Causation in Negligence Law:

The Problem of Proving the Impossible (or how to get your money without passing go)

by

Andrew Barker

A thesis submitted in conformity with the requirements for the Degree of Master of Laws

Graduate Department of Law University of Toronto

8 Copyright Andrew Richard Benedict Barker 1999

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Abstract

Causation in Negligence: The Problem of Proving the Impossible

by

Andrew Richard Benedict Barker

A thesis submitted in confonnity with of the requirements

for the Degree of Master of Laws

Graduate Department of Law

University of Toronto

It is fundamental for liability in negligence Law that a plaintiff first shows that the

negligent act of the defendant caused her injury. There are a p u p of cases. however,

where a p la in t s has succeeded in her daim, without fuifïlling this requirement, because

it was impossible for her to do so. These cases are often seen as presenting a

fundamental challenge to the need for proof of a causal relation in negligence law. Many

attempts have been made to avoid this challenge by reference to alternative bases for

identifying parties, and recognition of different forms of injury to a plaintiff. This thesis

considers these cases within the accepted structure of tort law, that requires proof of a

causal relation and awards compensation on an 'al1 or nothing' basis.

Table of Contents

. ............................................................... PART 1 INTRODUCTION -1

PART n - PROOF OF A CAUSAL RELATION ................................. 2

The Causal Relation in Negligence Law ............................................... 8

The Burden of Proof .................................................................... -13

The Standard o i Proof ................................................................... 14

The Function of Causation in Negligence Law ..................................... 15

PART III . A SITUATION OF IMPOSSIBILITY ............................... 17

What is 'A Situation of Impossibility'? .............................................. 18

(a) Certainty of injury to the Plaintrxand Negligent Act by the Defendant

................................................................... 19

0) The Reasonableness of the Situation of lmpossibiliîy .................... 20

A Situation of Impossibility . Wbat it is Not.. ....................................... 21

The Burden of Proof and the Failtcre ro Prove Causarion. ................. -22

(a) Sutcient Evidence to Determine Causation ...................... 23

(ô) imuflcienr Evidence to Determine Causarion - Further

Evidence Available ................................................... 24

(c) Insuflcient Evidence to Determine Causation - No Further

Evidence Available ................................................... 25

... ......................... The Spoliation of Evidence ..................... .. .. -27

PART IV O A STRUCTURE FOR THE CASE LAW .......................... 30

........................................................... The Dynamics of a Structure 31

... t l l

Degrees of Uncertainty. .......................................................... 32

............................. Tortious and Non-Culpable Competing Causes -37

.......................................................... A Structure for the Case Law 38

......................................................................... Category I .39

Category 2 .......................................................................... 42

Category 3 .......................................................................... 46

Category 4... ....................................................................... 49

Category 5 ......................................................................... 5 4

Cafegory 6... ..................................................................... 3 7

PART V . A RATIONALE FOR CASES INVOLVING A SITUATION

OF IMPOSSmILITY ........................................................................ -60

The Unenforceable Duty ................................................................. 61

The Ahtztre of an Unenforceable Duty .......................................... 62

The Nature of the Evidential Gap ............................................. ..64

The Signzjicance of the Unenforceable Duty .................................. 65

The Requirement of Fault. .............................................................. 65

The 'Innocent ' Plainrzfl .......................................................... -66

Fault on the Part of the Defendant ............................................. -67

(a) Creating the Siruarion of impossibility ........................... -68

(b) Foresight of the Situation of hpossibility ....................... -69

Certainty of Wrongful Injury .......................................................... 72

.................................... The Degree of Uncertainty of a Causal Relation 75

Substantial Possibility of Cause in Fact vs . Speculation ................. - 7 6

Reversing the Burden of Pro of. ................................................. -78 ................................................................ Inferring Causation 79

PART VI . CONCLUSION ................................................................. 82

Part 1 - Introduction

PART 1 - INTRODUCTION

Example 1'

A was the passenger in a car that was hit fiom behind by a car driven by B. The

impact forced A forward into the dashboard. and she suffered a concussion. Two

months later deahess in both of her ears developed. She consulted a number of

doctors after the accident, only one of whom diagnosed her with deafhess. She

brought an action for damages against B alleging that her deafhess was caused by

the collision, but at trial only called evidence fiom the doctor who had diagnosed

her deafhess. Her claim failed because she had not called evidence fiom the other

doctors she consulted.

Example 22

A was sitting in his car when he was hit fiom behind by a car driven by B. The

impact forced A's chest into the steering column, causing extensive bruising to

his chest. Unknown to A at the time. he had a deep-seated growth in his chest and

it was subsequently discovered that this growth was malignant. While the

malignancy codd have been caused by A's impact with the steering column, no

medicai witness was able to Say that this was anything more than a possibility. It

may already have been mdignant. or subsequently have becorne so. A's claim

against B for compensation failed.

I The facts of this example are taken fiom the decision in Levaque v. Corneau et. al. [1970] S C R 1010 (S.C.C.).

* The facts of this example are taken fiom the decision in BZackstock v. Foster [1958] S.R (N.S.W.) 341.

Part 1 - Introduction

Example 33

A worked in B's factory emptying brick kilns, and in the course of his work he

developed dennatitis fiom his exposure to brick dust. B was not negligent in

exposing A to brick dust while at work. However, it was negligent in not

providing showering facilities to its workers to allow them to wash after work-

Medical witnesses were unable to Say whether A developed the dermatitis while

he was working, or whether he developed it after he finished work and before he

was able to have a shower at home. Although A was unable to prove when the

dermatitis developed, he was successfiil in his claim.

What is the difference between these three examples? In al1 examples it was a possibiiity

that B's act caused A's injury, yet A was successfiil only in exarnple 3. In none of the

examples could A prove that B caused the injury. yet A's clairn succeeded in example 3.

In exarnple 1, A's daim failed because she had not brought al1 relevant evidence before

the court. In example 2 it was clear that there was no fiirther evidence that could have

been brought before the court, but A still failed in his claim. In example 3 there was again

no further evidence that could have been produced. but A was successful in his claim.

How can these differences between cases which in rnany ways seem alike be explained or

even justified? In a tort system of compensation. that requires proof of a causal relation

to establish liability, how can B in example 3 succeed?

This thesis attempts to answer some of these questions. Examples 2 and 3 both raise the

problem for the plaintiff of a 'situation of impossibility' of proving a causal relation

between the negligent act of the defendant and the injury to the plaintiE. Understood in

these te-, the examples raise two distinct questions; what is it that is different about

cases involving a situation of impossibility in cornparison to the ordinary case where a

plaintiff fails to prove a causal relation (i.e. the distinction between example 1 and

The facts of this examp le are takcn fiom the decision in McGhee v. Nalional Coal Board [ 1 9731 1 W.L.R 1 ( H L . , Scot.) [hereinafler McGhee].

Part 1 - lnuoduction 3

exarnples 2 and 3), and why are not al1 cases involving a situation of impossibility treated

the same way (Le. the distinction between examples 2 and 3). The focus of this paper is

on the second of these questions, and in providing an understanding of how and why a

plaintifT can suçceed in her clairn despite the impossibility of proving causation.

However, in c o n s i d e ~ g and defrnùig that problem, the answer to the first of these

questions d l also becorne apparent.

This paper suggests a p ~ c i p l e d basis for distinguishing between examples 2 and 3. in

most cases involving a situation of impossibility. if the daim of the plaintiff must

necessarily fail because she is unable to prove a causal reiation, there are a number of

Iegitimate policy concerns that may arise on the facts of any case. In particular, the

potential for the creation of an unenforceable duty on the defendant, the comparative fadt

of the parties in creating the situation of impossibility. and the possibility that a plaintiff

who has clearly suffered a wrongful injury \vil1 not be compensated or a defendant who

has inflicted a wrongfùl injury will not be required to compensate. These concems

explain why cases involving a situation of impossibility are sometirnes treated differentiy

by the courts, and expiain in part the difference between cases like example 1, and

examples 2 and 3. However, the presence of any one of these factors does not explain

when a court will allow a plaintiff to succeed in such cases. This paper will argue that

this issue is determined by the extent to which a court is able to vindicate the necessity

for proof of a causal relation in spite of the impossibility of proving such a relation. The

courts have required as a minimum proof that the act of the defendant either contributed

to the injury to the plaintiff, and could have been sufficient or necessary to have caused it,

or at the very least that there was a substantial possibility that it caused or contnbuted to

the injury, and could have been suficient or necessary to have caused it, This

requirement can be seen as a vindication of the necessity for proof of a causal relation to

the extent thut it is possible in cases invo lving a situation of irnpossibility .

The paper presents this argument in three stages. The first stage (Parts II and III)

introduces the problem of cases involving a situation of impossibility, and provides the

context within which the ensuing discussion \vil1 take place. There is £kt. in Part II, a

Part 1 - Introduction 4

brief discussion of the ordinary requirement for proof of a causal relation, This is the

requirement that the plaintiff must prove. on the balance of probabilities. that the

defendant's negiigent act caused her injury. If she fails to prove this, her claim will fail.

This is referred to as the 'ordinary requirement for proof of a causal relation'. Cases

invoiving a situation of impossibility challenge this requirement because if a plaintiff

were to succeed in her clairn, she would be successful even though she is unable to

establish a causal relation.

Part III then considers what is involved in a situation of impossibility, and in doing so

gives some explanation of the distinction between example 1, and examples 2 and 3. A

broad definition for cases involving a situation of impossibility is suggested. Such a

situation will arise where the evidence that is before the court allows no decision to be

made on the question of causation, and no Eùrther evidence that could help to resolve this

uncertainty either exists or at any time existed- This definition is intended to be

descriptive of the cases, and accordingly its proof must corne in the detailed consideration

of the case law that will follow. However. some attempt is made at this stage to

distinguish cases within this definition fiom cases that do not raise problems of

impossibility. Cases involving a situation of impossibility can be distinguished fiom

other cases where the plaintifYs claim fails because she is unable to establish a causal

relation. In the majority of those cases, the plaintiff fails either because the defendant's

act did not cause her injury, or because she has failed to bnng al1 relevant evidence

before the court. This is not true of cases involving a situation of impossibility. because

there is no further evidence that can be brought before the court. Cases involving a

situation of impossibility can also be distinguished fiom cases involving the spoliation of

evidence. in those cases further evidence that would tend to establish the causal relation

at some point existed, or possibly still exists, but has not been brou@ before the court

either because one of the parties to the litigation has destroyed it or because they have

refüsed to produce it. Again these cases cm be distinguished from cases involving a

situation of impossibility because hrther relevant evidence did at one stage exist (or still

does exist).

Part i - Introduction 5

The second stage of the argument is in Part IV. Here we consider in detail cases that

involve a situation of impossibility- The cases are organised by reference to two

variables that reflect the extent of our knowledge of the causes of the plaintiffs injury;

the degree of uncertainty as to a possible causal relation between the injury and the

defendant's negligent act (moving from a situation of certainty of contribution to the

injury, to a substantiai possibility of a causal relation. to such a relation being a matter of

speculation), and whether we know that the competing causes of the plaintiff s injury are

tortious. Use of these variable suggests a structure for considering these cases which is

both descriptive of the case iaw, and also reflects a progression fiom a situation of

greatest knowledge of a plaintiff s daim (where we know the defendant has suffered a

wrongfûl injury and the defendant has at Ieast contributed to that injury), to a situation of

least knowledge (where it is simply speculation to assert that the defendant caused the

plaintiff s injury and it is unknown whether the injury is even wrongfûl). However, this

structure, while being a useM way of thinking about the cases, does not tell us why cases

involving a situation of impossibility are treated any differently fiom other cases where a

plaintiff fails to prove causation.

The third and final stage of the argument is in Part V where we consider the difference

betsveen cases similar to examples 2 and 3. From the discussion of the case Law in Part

IV, four characteristics emerge fiom the cases as possible explanations for this

difference: the potential for 'guilty' defendants to escape liability, the comparative fault

of the parties in creating the situation of impossibility, the certainty that the plaintiff has

suffered a tortious injury, and the degree of uncertainty of a causal relation. The papa

suggests that whife the first three factors are important in understanding why a court

would treat these cases differently, the true point of distinction, as suggested earlier, is

the extent to which the court is able to vindicate the causal relation. Where the causal

relation is simply a matter of speculation, the courts cannot (and indeed do not) impose

liability on a defendant, and in doing so maintain the integrity of the causal relation.

Before finishing this introduction a few words should be said about the limits of this

paper. It is ultimately intended as an analysis of the case law according to what are the

Part 1 - Introduction 6

generdry accepted principles of tort law, and in particular, the necessity for proof of

some causal relation between the defendant's negligent act and the injury to the plaintifT,

and the 'dl-or-nothing' character of compensation in tort Law. The paper attempts to

understand the case law on its own terms. justiQing the decisions according to the

principles that the cases themselves view as pararnount. It accordingly does not consider

some of the alternative approaches that have been taken to the problem of impossibility

of proving causation, such as the doctrines of loss of chance4 or enterprise liability.' The

loss of chance approach is not considered because ultimately it is not concerned with

questions of causation, but rather the types of loss that are recognised by the courts.6 The

enterprise liability approach is not considered because it abandons the requirement for

proof of a causal relation in favour of liability based on the probability (or risk) of such a

causal relation.'

The second question that is not considered in this paper is that of the appropriate remedy

in a case involving a situation of impossibility. There has been substantial debate in

recent years over whether a court should reverse the burden of proof or simply infer a

"The exact defmition of 'loss of chance' is unclear, but it is generally accepted that it refers to the loss of an opportuniv to obtain or receive a desired outcome; for sxarnple, recovery fiom a persona1 injury." M. Lunney, "What Price a Chance" (1995) 15 Legal Stud, 1.

The doctrine of enterprise Iiability refers to the "imposition of Iiability upon each member in industry who manufactures or produces product which causes injury or harm to consumer and apportions Iiability of each member of industry by reference to that member's share of market for product" H. C. Black, Black's Law Diciiomty, 6' ed. (St Paul, Minnesota: West Publishing Co.. 1990) at 53 I .

6 See J. Stapelton, "The Gist of Negligence Part II: The Relationship Between "Damage" and Causation" (1988) 104 L.Q.R 389 at 390 - 400; D. Gerecke. "Risk Exposure as Injury: Alleviating the Injustice of Tort Causation Rules" (1990) McGiIl L. J. 797; T. Hill. "A Lost Chance for Compensation in the Tort of Negligence by the H o u e of Lords" (1991) M.L.R. 51 1. For exarnptes of the extensive literature on the doctrine of 'Ioss of chance' see H. Reece, "Losses of Chance in the Law" (1996) 59 M.L.R. 188; S. M. Waddams, "Damages: Assessment of Uncertainties" (1998) 13 J.C.L, 55; D. P. T. Price, "Causation - The Lords' Lost Chance" (1 989) 38 Int'l. & Comp. L.Q. 735; M. Staunch, "Causation, Risk, and Loss of Chance in Medical Negligence" (1997) 17 Oxford J. Legal Stud. 205; J. G. Fleming, "Probabilistic Causation in Tort Law" (1989) Can. Bar Rev. 66i; B. Coote, "Chance and the Burden of Proof' (1988) Austi. L.J. 761.

7 See generally, A. G. Celli, Jr., ''Towards a Risk Contribution Approach to Tortfeasor Identification and Multiple Causation Cases" (1990) 65 N. Y. Uni. L. Rev. 635; L. A. Alexander, "Causation and Corrective Justice" (1987) 6 Law & Phil. 1 at 14; Fleming, ibid

Part I - Introduction 7

causal relation as a response to these cases.' The question is largely irrelevant in this

paper, because on either approach the effect would be to impose iiability on a defendant

without reference to the need for proof of a causal relation? The question this paper

addresses is how to resotve cases involving a situation of irnpossibility while still

maintainhg the integrity of the causal relation. and why we would do so. The integrity of

that reiation does not depend on whether a causal relation is inferred, or the burden of

proof reversed, since on either approach, where causation is impossible to prove, the

result is an assertion of liability on the defendant based not on any causal principle, but

rather on broder grounds of policy.

Finally it should be noted that this paper deals primarily with cases involving negligence.

The reason for this is simply that the majorïty of cases involving a situation of

impossibility arise within the law of negligence. and a need to retain some limits on the

potential scope of the discussion in this paper. Howevei it is clear that the problems

considered in this paper are not Iimited to negligence law,Io nor necessarily to the law of

torts." The understanding suggested in this paper may prove to be equally applicable to

the problem of irnpossibility in these contexts, although that argument will need to be

made at a tater date.

' This debate started with the decision in McGhee. supra at note 3. where Lord Wilbedorce suggested a reversal of the burden of proof in cases involving a situation of impossibility. This approach was favoured by a number of courts. See, for example, the decisions in Chrk v- McLennan [1983] 1 Al1 E.R 4 16; Fiageruid v. Lane [1987l3 W.L.R 249 (C.A.); Bryce v. Swan Hunfer Group [1988] 1 Al1 E.R- 659; Letnik v. Metropofiran Toronto (Municipaii~) (1 988) 39 D.L.R. (Ont. CA-). nie approach was later rejected by the House of Lords in its decision in Wilsher v. fisex Area Hedth Aurhority [1988] 2 W.L.R. 557 (H.L.) mereinafter Wilsher] and by the Canadian Supreme Court in S n d v. Farreif (1990) 72 D.L.R. ( 49 289. See generally R Roth, "Causation and the Burden of Proof: An Age Old DiIemma and a New Age Approach" (1992) 14 Advocates' Q. 70 for a review of this debate-

9 This point is discussed tiirther in Part V when considering alternative theories for resolving cases invotving a situation of impossibility that vindicate the need for proof of a causal relation. See text accompanying notes 134 to 139 above.

'O The problern often arises, for example, in the context of nuisance actions. See Lumbton v . Mellish LI9841 3 Ch. 163.

I l An example of a simifar problem arising in the Iaw of contract is the decisior, in Rhesa Shipping Co. S.A. v. Edrnunds [1985] 2 Al1 E.R 712 (H.L.).

Part 1 - Introduction

Cases involving a situation of irnpossibility are cases that are concerned with the

requirement for proof of a causal relation in tort law. Tort law, and in particular the law

of negligence with which this paper is primarily concemed, requires that before a plaintZf

can recover damages fiom a defendant for any injury she has suffered, she must first

show that on the balance of probabilities a tortious act of the defendant was the cause of

her injury, If she cannot establish this, her claim will fail, This requirement for proof of a

causal relation has three parts. Al1 are relatively uncontroversial and can be stated in

short compass. First is the need for proof of a causal relation between the negligent act of

the defendant and the injury to the plaintiff. Second is the well established principle that

it is the plaintiff who carries the burden of proving this causai relation. Third is that it is

the plaintiff who must prove the existence of a causal relation on the balance of

probabilities. These three features are considered in this Part.

This paper does not consider the question of why causation matters. either in moral,12

structural, l 3 or purposive terms.14 It accepts the requirement as one firmly entrenched in

the case law, and more importantly, one whose importance is recognised in the very cases

" For discussion of the moral significance of the causal requirement in tort law see J. J. Thornpson, "The Decline of Cause" (1987) 76 Geo. L. J. 137: P. F. Rothstein, "Causation in Torts, Crimes. and Moral Philosophy: A RepIy to Professor Thompson" (1987) 76 Geo. L. J. 15 1; C. H. Schroeder. "Causation, Compensation, and Moral Responsibility" in D.G. Owen ed.. Philosophical Foundations of Tort L a w (Oxford: Clarendon Press, 1995) at 347.

" For examples of writers who consider the importance of causation in tems of how it expresses the structure of the compensation/liability regirne inherent in tort law see E. J, Weinrib, "Causation and Wrongdoing" (1987) 63 Chi-Kent L. Rev. 407 [hereinafler "Causation and Wrongdoing"]: E. J. Weinrib, The Idea of Private Law, (Cambridge: Harvard University Press, 1995) [hereinafier Private Lcnu]; J- L. Coleman, "Property, Wrongfiilness and the Duty to Compensate" (1987) 63 Chi-Kent L. Rev. 451; R A. Epstein, "A Theory of Strict Liability" 2 J. Legal Stud. 151 (1973); A. Ripstein & B. C. Zipursky, "Corrective Justice in an Age of Mass Torts" in J. Postema ed., Philosophy and Tort Lac?. (Cambridge University Press, forthcoming).

14 For examples of writers who understand the causation requirement purely in tems of how it achieves a broader social purpose see G. Calabresi, "Concernin_g Cause and the Law of Torts: An Essay for I-farry Kalvem, Jr." 43 Uni. of Chic. L- Rev. 69 (1975); L. A. Alexander, supra note 7.

Part II- h f of a Causal Relation 9

that have considered this problem- Yet it is usefûl to consider, in descriptive terms, the

role of causation in determining liability in negIigence Law. Clearly proof of a causal

relation connects a plaintiff to a defendant. and creates the relationship that is at the heart

of liability in tort Iaw. But where causation is established between a wrongful act of a

defendant and an injury to a plaintiff, causation tells us two important things: that the

injury to the plaint= is a won@ injury. and that the defendant's negligent act has

inflicted an injury. It shows that the plaintiff is entitled to compensation and that the

defendant is required to compensate. As this point is of some importance, it is considered

brîefly at the end of this Part,

The Causal Relation in Negligence Law

Before Iiability can be imposed on a defendant for any injury suffered by a piaintiff, it

must f i be shown that the negligent act of the defendant caused the injury to the

plaintiff. This requirement is seen as fundamental for liability in negligence law? It is

has been unanimously accepted by the authors of the leading te- on the law of torts,'6

and repeatedly affinned by the highest courts of the major ~ornmonwealth jurisdictions."

IS See the authorities referred to supra note 13. See also J. J . Thomson, "Remarks on Causation and Liability" (1984) 13 Philosophy. & Pub. A f f 10 1. reprinted in J. .I. Thomson, Rights. Resriturion. and RISk, (Cambridge, Mass.: Harvard University Press, 1986) 192; J. j. Thompson, "The Decline of Cause", supra note 12; L. A. Alexander, supra note 7.

16 Se+ I. G . Fleming, The L a w o/Torrs. 9<h ed. (Sydney: The Law Book Company, 1998) at 1 1 8: L. N. Klar, Torr Law, 2nd ed. (Toronto: Carswe 1 1, 1996) at 3 1 9; Ci. H. L. Fridrnan, The Law of Torts in Canada, vol, 1 (Toronto: Carswell, 1989) at 322; A. M. Linden, Canadian Tort Law, ed. (Toronto: Buttenvorths, 1 993) at 98; K. Cooper-Stephensen. Persond lnjury Damages in Canada, zd ed. (Toronto: Carswell. 1996) at 748; M. Brazier ed., Clerk and LindeII on Torrs. 17& ed- (London: Sweet & Maxwell, 1995) at 39; W. V. H. Rogers, Winfield andJofowicz on Tort. 14& ed. (London: Sweet & Maxwell, 1 994) at 147; M. BraPer, Street on Torrs, 9* ed. (London: Butterworths, 1993) at 249; F. Trindade & P. Cane, The Law of Torrs in Ausrralia, 2" ed. (MeIbourne: Oxford University Press. 1993) at 447; S. Todd ed., The Lmv of Torrs in lVew Zealand, 2" ed. (Wellington: Brookers, 1997) at 1025 - 1026.

" Bonnington Castings v. Wardlaw [ 1 9561 A S . 6 I 2 (H .L. (Scot.) [hereinafier Bonningion Castings]; Wikher, supra at note 8; Kay v. Ayrshire & Arran Heairh Board [ 19871 2 ALI E.R 4 17 (H.L.) [hereinafier Kay v. Ayrshire]; Bolilho v. City and Hackeny Heafrh Authority [1998] A.C. 232 (H.L.(E,)); Snell v. Farrell, supra note 8; Alhey v. Leunari [ 19971 1 W. W.R, 97 (S.C.C.); Murch v. E& M. ff- Srramme P@ and anorher ( 1 990 - 1 99 1 ) 1 7 1 C.L,R 507 (H.C.) [hereina fier March v. Srrumare] .

Part II- Proof of a Causal Relation 1 O

The necessity of this requirement can be illustrated by the decision in Burnerr v, Chelsea

and Kensington Hospita1 Management Cornrnittee." In that case, the deceased

unknowingiy consumed tea which had been poisoned with arsenic. Within a short period

of time he became violently il1 and went to the defendant's hospitai to seek treatment,

However, the nurse at the hospitd and the doctor with whom she consulted, sent him

home without providing any treatment, believing he had a simple case of gastritis. The

deceased died some hours later and his estate brought a ciaim against the hospital for the

negligent treatment he received. The court found that the defendant was negligent in not

providing proper treatment for the plainta but heId that the plaintiff had not shown that

this negligence caused the death of the deceased. Rather, the evidence established that

even if the deceased had received proper treatment. he would still have died- The

plaintiff s daim accordingly failed.

While the necessity for proof of a causal relation is easily stated, its application in

practice is more problematic.'9 It is first necessary to recognise that causation in the law

is concerned with a common sense standard rather than any scientific or philosophicai

notions of cause.20 It is to be understood ''as the man in the Street, and not as either the

scientist or the metaphysicia would understand it."" This is seen as justified by the

Court3 broader concem in a civil action with fixing liability. rather than the scientific

concem of determinhg cause as a matter of precision.z Yet a common sense standard

-- -

'* [1969] Q.B. 429.

19 Professor Fleming has noted; "Causation has plagued courts and scholars more than any other topic in the law of torts." See Fleming, supra note 16 at 2 18. See also Arnotr v. O 'Keefe LI9771 I.R.I. at 19 per Kenny S.

'O The classic discussion of the concept of 'common sense' causation is H. L. A. Hart 8: A. Honore, Causacion in Law, 2"d ed (Oxford; New York: Clarendon Press, 1985).

" Yorkshire Dole Steamship Co. Ltd v. Minister of War Transport Cl9421 A C . 691 (H.L.) at 706 per Lord Wright.

"The object of the civil inquiry into cause and consequence is to fix liability on some teasonabte person and to give reparation for damage done . . . The trial of an action for darnage is not a scientific inquest into a mixed sequence of phenomena, or an historical investigation of the chapter of events ... It is a practical inquiry." Wefd-Bfundeff v. Stephens [1920] A.C. 956 (H.L.) at 986 per Lord Sumner. For a more recent discussion of the difference between causation in science and philosophy, and causation in Iaw. see Mwch v. Sframare, supra at note 17 at 5 15 - 5 17 per Mason C.J., and 528 - 536 per McHugh J. For discussion of the idea of certainty of an adjudicative fact, and the fundamental difference between scientific and judicial

Part II- Proof of a Causal Relation I l

for causation appears to be an inherently value laden inquiry, susceptible for use as a

device for giving effect to othenvise unarticulated policy c o n c e r n ~ . ~ Accordingiy,

analysis of the causal requirement in tort law has sought to distinguish the specific factual

matters involved fiom the broader issues of policy. This is the distinction between cause

in fact and cause in la^?^

The first question usually asked in any causal inquiry is whether the defendant's act was a

'cause in fact' of the plaintirs injury.'* This is an inquiry into the relation of cause and

effect, and as such has similarities to 'scientific' notions of cause, It is intended as a

policy neutral question, aimed at establishing that the defendant's act was at least one of

the causes of the plaintiff s injury? Because crws involving a situation of irnpossibility

usually involve a problem in establishing cause in fact, sornething should be said about

what the courts treat as proof of this requirement. This question is usually deterrnined by

the application of the inclusive 'but for' test. The decision in Barnett v. Chelsea und

Kensingron Hospital Management Cornmittee is a classic example of the operation of this

test. If a cause satisfies the 'but for' test, it is usually described as a 'necessary' cause of

the plaintiff s injury, in that without the defendant's negligent act, the plaintiff would not

inquiries, see H. M. Hart, "Some Aspects of Evidence and Inference in the Law", in D. Lerner ed., Evidence and Inference, (The Free Press o f Glencoe, 1958); M. Radin. "The Permanent Problems of the Law" (1929) 25 Corn. L. Quart. 1; J. B. Weinstein. "The Difficulties for Devising Rules for Deteminhg Tmth in Judicial Trials" (1 966) 66 Colum. L. Rev- 223.

'3 For exarnple, see the judgment of McHugh J in March v. Sframare, supra note 17.

'' For discussion of the general principles of cause in fact and cause in law see Fleming, sztpru note 16 at 2 18 - 354; Rogers, supra note 16 at 147 - 1 74; Klar, supra note 16 at 3 19 - 363. '5 See generally D. W. Robertson, "The Common Sense of Cause in Fact" (1997) 75 Tex- L. Rev. 1765; N. J. Mullany, "Common Sense Causation - an Australian View" (1992) 12 Oxford J, Legal Stud. 43 1; E. J. Weinrib, "A Step Forward in FactuaI Causation" (1975) 38 M.L.R, 518.

26 Whether this inquiry can ever be purely one of fact has been the subject of much debate. See, for exarnple, W. S. Malone, "Ruminations on Cause-in-Fact" (1956) 9 Stan. L. Rev. 60 who argues that the formulation of factual issues is as much a matter of policy as questions of proximate cause. Another exarnple of an analysis seeking to emphasise the policy basis of the cause in fact inquiry is G. Calabresi, supra note 14. The most wel1 known argument for distinguishing policy considerations from the factual aspect of the causal inquiry is that of Hart & Honore. supra note 20. See also A. C. Brecht and F. W. Miller, The Test of Facîuat Causation in Negligence and Strict Liabiliry Cases, (St Louis: Washington University Studies, 196 1). These different positions are reviewed by R W. Wright, "Causation in Tort Law" (1985) Cal. L. Rev. 1737, where he also makes a powerful argument for maintaining a distinction between matters in the factuaI causation inquiry and issues of responsibility for h m .

Part II- P m o f of a Causal Relation 12

have suffered the injury?' In these terms the negligent act can also be described as

'sufficient' to have caused the injury. in that given this set of conditions, '%e

consequence must f o l l o ~ " . ~ ~ Yet while it appears that al1 'necessary' causes. in the sense

of being a 'but for' cause, are causes in fact, not al1 causes in fact appear to involve

'necessary' causes in the 'but for' sense." In particular, in a limited number of instances

where there are competing sufficient causes, courts have preferred to establish causation

by reference to the more general description of the defendant's conduct as 'suficient' to

have caused the plaintiffs i n j ~ r y ' ~ The classic illustration of this is the decision in

Anderson v. Minneapolis ~ a i l w q ? ' where f ies from two separate sources combined to

destroy the plaintifYs house. Although each cause was 'suficient' to have destroyed the

plaintiffs house (in that, viewed in isolation, it would have k e n necessary to have

caused the injury), neither cause could be descnbed in the 'but for' sense as 'necessary'.

27 The discussion here about necessary and sufficient causes refers in part to the analysis of Cooper- Stephensen, supra 16 at 75 1 - 752. Wright, Ibid, sugcsts that al1 questions of cause in fact require proof of both necessity and sufficiency. That question. however, does not necessarily have to presuppose only one set of conditions for each injury. There can be. and in cases of muitiple suficient causes clearly are, more than one set of conditions sufticient to have caused the injury. The question on his analysis is whether the defendant's negligent act was a member of a set of necessary conditions that were suficient to have caused the injury. His analysis has been supported by a number of writers. See. for example, Fleming, supra note 16 at 2 19; Brazier ed.. Sfreer on Torrs. supra note 16 at 249.

" Wright, supra note 26 at 1789.

'P This distinction is often captured in the statement that the 'but for' test is a test of inclusion rather than exclusion. See C. E. Carpenter. "Concurrent Causationn (1935) 8 U. Pa- L. Rev. 941 at 948: Weinrib, supra note 25 at 521 - 522.

The concept of the set of actual conditions that must be suficient to have caused the injury is problematic. The view that is adopted here is that it refers to a set of actual conditions, although in a more narrow sense than that suggested by Wright. That is. a situation which did in fact exist, such as one of the fues in the merged fve case, and assessing the sufEciency of that act combined with the background conditions, to the excIusion of the other competing cause. Wright, in an effort to explain cases such as Corey v. Havener (1902) 65 N.E. 69, where it did not appear that it was established that the act of either defendant was suficient to have caused the injury (see discussion infra note 86) adopts a broader approach to the need for the sufficiency of an arma1 set of conditions. On his view, a set of actual conditions can include those conditions that were present, but also a subdivision of each set of actual conditions. Thus, in the rnerged fue example. if one of the causes was cleariy suficient to have caused the fire, and the other insufficient, the insufficient fire was still a cause because "it was necessary for the sufficiency of a set of actual antecedent conditions which included another fire (the first) that was "ut feusr large enough for the injury if it merged with a fire the size of the second fire-" See Wright, supra note 26 at 1793.

" (1 908) 179 N.W. 45.

Part II- P m f of a Causal Relation 13

The use of these two ternis can be a source of endless confision. Ultimately al1

necessary causes can be descnbed as suficient. as a cause is only necessary in

conjunction with other conditions which together are sufficient to cause the injury, and al1

sufficient causes are necessary within their own particular set of conditions. In this paper

the term 'necessary' will be used to refer to causes in the 'but for' sense, in that without

that cause, the injury would not have occurred. A cause will be described as 'sufficient'

where the cause fails to satisfy the 'but for' test. but would have been necessary on a set

of conditions that did occur absent the other competing cause.

Once it is established that the defendant's act was a factuat cause of the plaintiff s injury,

the problem becomes one of determining whether the defendant's act shouid be regarded

as the relevant cause of the plaintiffs injury for the pwposes of determining liability.

This is the problem of detennining the iimits of the defendant's liability for the

consequences of her negligent act. Defining those lirnits is one which, ultimately, has

been described as deQing "verbal defmition in fixed r ~ l e s . " ~ ~ In judicial language, it is

captured within the concept of 'comrnon sense' causation. While this requirement has

been the subject of extensive debate, the accepted standard now appears to be that, at the

very least, the type of injury sufTered by the plaintiff must have been foreseeable.

The Burden of Proof

It is weI1 established that the burden of proving causation rests with the plaintiff. While

this requuement is probably not fundamental in the same sense as that of the need for

proof of a causal relation, it is equally well established. It is acknowiedged by the

authon of the leading texts on tort law.j3 as well as the leading courts of the major

3 1 Fleming, supra note 16 at 232.

" See Fleming, supra note 16 at 225 - 227; Klar. supra note 16 at 407 - 409; Fridman, supra note 16 at 322; Cooper-Stephensen, supra note 16 at 754; Btazier ed., Clerk and LinakeII on Torts, supru note 16 at 39; Brazier, Street on Torts, supra note 16 at 240 - 242; Trindade & Cane, supra note 16 at 437; Todd ed., supra note 16 at 1030.

Part II- Proof of a Causai Relation 14

commonwealth j~risdict ions.~~ More importantly. it has recently been re-affirmed by the

House of Lords and the Canadian Supreme Court in the face of challenges presented by

cases such as those considered in this ~ a p e r . ~ * The nature of the burden of proof of

causation will be considered in more detail in the following ~ h a ~ t e r . ~ ~

The Standard of Proof

The final requirement to consider is the standard the plaintiff must satisw in proving

causation. It is ciear that as any question of causation involves a question of past historic

fact, the ptaintiff must prove the existence of a causal relation on the balance of

pr0babilities.3~ Once a plaintiff has established this much, the fact of a causal relation will

be treated as a matter of certainty. As was stated by Lord Diplock in MaZZett v

McMonagle: "ln detennining what did happen in the past a court decides on the balance

of probabilities. Anything that is more probable than not it treats as certain."38 As is

clear from the quotation. the balance of probabilities test incorporates within it a degree

of uncertainty, an uncertainty which in some cases can be subs tant ia~ .~~ However, the

34 Bonnington C'ings. supra note 17; Horson v East Berkshire Area Health Authority [ i 987) 1 A.C. 750 (H.L.) [hereinafier Horson]; Wilsher, supra note 8: Kay v. ..lryshire. supra note 1 7: Snell v. Farrell, supra note 8.

35 See the discussion supra note 8.

36 See the discussion inza notes 53 to 62and accompanying text.

37 See Fleming, supra note 16, at 225 - 337; Klar. supra note 16 at 408; Cooper-Stephensen. supra note 16 at 754; Brazier, CIerk and LindreiI on Torts, supra note 16 at 383; R. F. V Heuston, Salmond and Herrston on rhe L a w of Torrs, 21n ed. (London: Sweet & MaxwelI, 1996) at 240; Todd ed., supra note 16 at 1030.

38 [1969] 2 Al1 E.R 178 (H.L.) at 190 - 191. See also Horson. supra note 34 at 793 per Lord Ackner, "Where causation is in issue, the judge decides that issue on the balance of probabilities. ..- Once liability is established .., the Ioss which the plaintiff has sustained is payable in hl!. It is not discounted by the extent to which he has faiIed to prove his case with 100 per cent. certainty." See also Arhq v- Leonafi [1997] 1 W.W.R 97 (S.C.C.).

39 The balance of probabilities test is usually thought of in terms of being a probability of at least 51% of the alieged fact having occurred. Such a formuiation would allow, in theory at least, a 49% probability of the alleged fact not having occurred. However research has indicated that the judge and jury generally require more than proof simply of a 5 1% probability. something more Iike a 75% probability. See R J. Simon & L-Mahan, "QuantiQing Burdens of Proof' (1 970-71) 5 Law & Soc, Rev. 3 19, referred to by J. G. Fleming in "Probabilistic Causation in Ton Law", supra note 6. See also D. Hanter, "The Civil Standard of Proof Uncertainty: Probability, Belief and Justice" (1994) 16 Sydney Law Rev. 506, in which he defends

Part II- Proof of a Causal Relation 15

Courts of England and Canada have rejected any attempt to reflect this uncertainty in the

award made in favour of the p la in t i~40 The approach is d l or nothing; either the plaintiff

can show that the act of the defendant was more probably than not the cause of her injury,

in which case she will recover the full value of her loss, or she will recover n ~ t h i n ~ . ~ '

The Funcrion of Causation in Negligence Law

in offering a descriptive account of the causai relation in negligence law. we must also

consider the function it fulfils in the assignment of liability. The question here is what

does proof of causation tell us about the plaintiff s claim? We are not concerned with the

wider issue of whether causation is a moraily relevant factor in determining liabilityp2 or

even assuming that it is morally relevant. whether the litigation structure of negligence

law reflects the significance of causation? Rather, the significance of the causal relation

is accepted, as it is accepted by the courts. and the question that is asked is what does

proof of causation tell us about the plaintiff s claim, and her entitlement to compensation

from the defendant. Understanding the function of causation in negligence law wiii be

important to us when c o n s i d e ~ g the problems created by cases involving a situation of

impossibility.

use of a more probable than not standard (51%) as a basis for accepting proof of causation over more evaluative standards such as a "persuasion" as to the existence of such a causal relation,

10 See Hozson. supra at note 34; Lafrriere v Larvson ( 1 99 1). 78 D.L.R (4h) 609 (S.C.C.). Although contrast the position in Austxalia in Malec v. ' C. Hurron Py Lfd (1990) 169 C.L.R. 638 (H.C.A.) Poseidon v. Adelaide Petroleum N.L. (1994) 68 A.L.J.R. 3 13 (H-CA-), These decisions are discussed by Lunney, supra note 4.

4 I [n this regard, the problem of proof of causation needs to be distinguished from the debate over compensation for loss of chance. The loss of chance approach to cases involving a situation of impossibility is to modify the type of injury that is to be cornpensated. For example, in a personal injury claim, rather than compensating for the injury itself, the plaintiff is compensated for the chance of avoiding the injury. It is not a debate about the nature of the causal relation, indeed it is clear chat even in a case involving a loss of chance, the plaintiff must still prove on the balance of probabilities that she had a chance which has been lost. See the authorities mentioned supra note 6.

42 For discussion of the moral significance of the causal requirement see the authorities mentioned supm at note 12.

43 See for example, Coleman, supra note 13.

Part II- Proof of a Causai Relation 16

At its most simple level, proof of a causal relation tells us that there is a relationship

between a party whose action might potentially cause injury, and a party who has

sufTered injury. The potentiality that the defendant's act may injure a person or their

property has crystallised into a specific injury to the plaintiff. We can Say that that injury

has been 'caused' by the defendant's act. There is a physical c o ~ e c t i o n between the two

facts. On a strict liability model for tort law. this is al1 causation does and indeed ail that

is necessary for determinhg liability? Yet negligence law has not adopted a strict

liability model of liability. Rather in also requires wrong-doing on the part of the

defendant. The question then is, with this element of c~rong-doing added, what does

causation tell us about the plaintiffs daim'?

First, once the element of wrong-doing is added to the defendant's act, we also know that

the injury that has been suffered by the plaintiff is a wrongfùl injury. It is an injury that is

recognised by tort law as grounding a right to compensation. Without proof of a causai

relation to the defendant's wrongfil act, the plaintiff has simply suffered an injtuy. Tort

law does not recognise such an injury as being relevant to the defendant's possible

liability or the plaintiff s entitlement to compensation. It only recognises injuries that are

caused by a wrong. Thus proof of a causai relation identifies the plaintiff as having

suffered a won@ injury, one which entitles her to compensation fkom a defendant.

Proof of causation also tells us something about the defendant's act. It tells us is that the

defendant's wrongful act has caused an injury. The potentiai for harm it created has

crystallised in an injury to a plaintiE To adopt the language of one comrnentator, it tells

us that the defendant has breached a duty of non-injury, as opposed to a duty of non-

injurio~sness.~~ We know that this defendant is not wholly innocent. She is required to

compensate the person she has injured.

44 See Epstein, supra note t 3.

*' Ripstein & Zipursky, supra note 13. There has been some debate as to whether causation is relevant in assessing the moral culpability o f the defendant. The argument that is made is that what negligence law is concerned about is the wrongfirIness o f the act o f the defendant. Whether that act caused any injury is a matter o f fortuity. See J. J. ïhornson, "Remarks on Causation and Liability", szrpra note 13; Weinrib, "Causation and Wrongdoing", supra note t 3; Weinrib, Private Law, supra note 13; Coieman. supra note 43. As noted earfier, this paper does not consider the difficult issue of the relevance or othenvise of

Part II- Proof of a Causal Relation

PART III - A SITUATION OF IMPOSSIBILITY

In the last Part we considered the nature of the requirement for proof of a causal relation

in negligence law. We saw that it is welt established that to found her claim. a plaintiff

mwt show on the balance of probabilities that the negligent act of the defendant caused

her injury. We also considered the function that causation plays in negligence law, and in

particular its identification of the injury that has been suffered by the plaintiff as a

won-gfui injury, or the defendant's act is one that has inflicted wronf l injury. We now

consider a type of case where it is impossible for the plaintfl to satisfy this requirement.

This type of case is referred to as one involving a 'situation of ùnpossibiliîy'.

We do not at this stage consider examples of cases that represent this situation. Our

concern here is to identiQ in general ternis the nature of a case involving a situation of

impossibility, and in particular to identiQ some of the charactenstics such cases will

share. This is done fmt by presenting a broad definition for such cases. This definition

is descriptive of the case law rather than prescriptive. Its ultimate proof \vil1 lie in

consideration of the cases in Part V. However. the description will allow us to

distinguish these cases fiom a range of other cases where a plaintiff fails in her daim

because she is unable to prove a causal relation. It will allow us to answer in part the first

question posed in the Introduction of what it is that is different about cases involving a

situation of impossibility.

-- ~ - -

causation in assessing the character of the defendant's act. Its concern is simply to see what it is that causation tells us about the plaintiffs daim and the defendant's act. CIearly where we know that the defendant's act resulted in injury, wve know more about the plaintiff s daim than if it is a possibility that the defendant's act caused no injury at all.

Part III- A Situation of Impossibility

What is 'A Situation oflinpossibiIity '

A situation of impossibility exists where the trier of fact, having heard al1 the evidence

brought before it, decides that there is insuficient evidence to determine either one way

or the other the existence of a causal relation between the negligent act of the defendant

and the injury to the plaintiff, and any M e r evidence that may have assisted the court in

determinhg this issue has at no stage existed. or couid not reasonably be brought before

the court by either Party.

As noted above, this definition is intended to be descriptive of a body of case Iaw, but if

we consider the process of proof in judicial proceedings, it is also a possibility that seems

likely to arise. Determination of facts in the judicial process is an inherently uncertain

activity. The law must "settle disputed questions of adjudicative fact by reliance upon

the ambiguous implications of non-fungible '-tracesy' - traces on human brains and on

pieces of paper and traces in the form of the unique arrangements of physical 0bje~t .s . '~~

While courts in the vast majority of cases are able to resolve these questions. often on the

bais of very limited evidentiai material. the situation may arise where facts simply do

not suggest a conclusion either way on the matter in dispute. The traces may themselves

be silent, or not in fact exist. In a system of dispute resloution, where evidence is Iimited

to that produced by the parties to the action. and a decision on disputed facts can only be

reached by reference to 'traces' of the occurrence of that fact, it seems certain that in

some cases those 'traces' will themselves not exist.

Before considering what a situation of impossibility c m be distinguished from. however,

there are two points that a i se fiom this definition that need m e r clarification:

(a) The fact that in al1 cases involving a situation of impossibility. it will

invariably have been shown that the plaintiff has suffered an injury and the

defendant has committed a negligent act;

--

46 Hart & McNaughton, supra note 22 at 52.

Part III- A Situation of Impossibitity

(b) It need only be unreasonable for M e r evidence to be brought before the

c o r n not impossible in any absolute sense.

(a) Certaine of Injury to the Piaint~ff and NegZigent Act by the Defendant

It is important to recognise that in cases involving a situation of impossibility, it will

invariably have been proved on the balance of probabilities. diat the defendant has

cornmitted a negligent act against the plaintiff. and that the plaintiff has herself suffered

an injury. This does not mean that before any question of causation can arise. an injury

to the plaintiff and a negligent act by the defendant must first be established. It may often

be the case, for example, that because there is clearly no causai relation between the act

of the defendant and the injury to the plaintiff that the court does not even consider

whether the defendant's act was negligent.'" Rather, in considering cases where the

impossibility of proving causation is the defining characteristic of the case (which is our

concem here), these two facts will almost certainly have been established."' I f a plainMf

is unable to show that she has suffered an injury. then there is no injury to whîch any

question of a causal relation c m be applied. The court is more likely to focus on this

failing, rather than the more difficult issue of the impossibility of proving a causal

relation. Similarly, if the plaintiff is unable to show a negligent act committed against

her by the defendant, it would be redundant to talk of whether that act caused her any

injury when even if that matter were answered in the affirmative, she would stili need to

show that the act was itself negligent. We are concemed here with the minimal situation

47 For example FYeekes v. McNulfy (1 898) 48 S.W. 809, where the question was whether the provision of fire escapes would have saved the life of the deceased. The court held; ''[Ilf the contention of counsel for the plaintiff ... were correct, and chat its breach would constitute actionable negligence, these questions are mere abstractions in this case, since no causal connection between the violation of the ordinance and the injuries sustained by the plaintiff is shown." (at 8 12 per McAlister J.).

48 This fact is recognised by Professor Robertson, when considering problem cases involving the issue of cause in fact, "No end of confusion results when academic and nonlawyer observes of the law's approach to factual causation forget that the issue never cornes up except in the context of a lawsuit in which the defendant's wrongfiil conduct and the piaintiff s injuries have been particularized." See Robertson, supra note 25 at 1769.

Part 111- A Situation of Irnpossibility 20

that c m arise involving a situation of impossibility. For that situation, it wili first have

been shown that the plaintiff has suffered an injury and the defendant has committed a

negligent act to the plaintiff.

Of more interest is the possibility that the plaintiff may be able to prove more than the

bare fact of a negligent act and an injury. yet still be unable to prove a causal relation

between the two. Here we need to refer to our earlier discussion of the role of causation

in tort law. Because a plaintiffcannot prove causation. it does not necessarily follow that

she will be unable to prove that her injury tvas wrongful. She rnay be able to show that

al1 possible causes of her injury were tortious. and indeed this is a common feature of

many cases involving a situation of impossibility."9 She may also be able to show not

just that the defendant's act was negligent. but that it inflicted a wrongful injury on

someone. We must note, however, that the second of these possibilities is one which

seldom arises. 50

(b) The Remableness of rhe Situation of Impossibiliry

The second feature that should be noted about our definition for cases involving a

situation of impossibility is that the requirement that there is no evidence that couid assist

in resolving the evidential uncertainty is one subject to reasonableness. The courts do not

require as an absolute that causation rnust be impossible to prove. There rnay be cases

where in theory proof of causation is possible but which still involve a situation of

impossibility. It is rather that it would in the circumstances be unreasonable to requke

49 For example Corey v. Havenet-, supra note 30, and Cook v. Lavis [1952] 1 D.L.R 1 (S.C.C.).

50 The reasons for this are unclear but probably result from the adversarial nature of the litigation process. In an action between two individual parties, the range of causes of the plaintiff s injury is an issue that is Iikely to be a well canvassed. The plaintiff will attempt to show that it was the defendant's act that was the cause of her injury, while the defendant that some other cause was to blame. In such an environment, it is not surprising that where causation cannot be proved. the court will sometimes still be able to characterise the competing causes as tortious. Yet whether the defendant's act injured some unidentified plaintiff seems a siightly irrelevant question to ask. The plaintiff wilt be trying to establish that the defendant's negligent act injured her and not some other person, while the defendant will be trying to show she injured no one at d l . The question is most likely to arise when the entire range of potential plaintiff s is before the court, and indeed the only examples of this possibility that the writer has identified are cases involving class actions where this was the case.

Part III- A Sidon of Impossibility 21

the plaintiff to prove the fact. This point cm be illustrated by the decision in Letnik v,

MunicipaIiîy of Metroploitan m or ont o.^ ' A ship owned by the defendant negligently

collided with a ship owned by the plaintiff. The plaintifYs ship appeared to s a e r only

minor damage in the collision, but two weeks later sank very suddenly, It was unknown

what caused the vesse1 to sink, and it was apparendy impossible for the plaintiff to prove

that it sank as a resuit of the collision. One of the arguments that was made by the

defendant was that this was not a situation of impossibility because the plaintiff could

simply raise the ship to establish the cause of its sinking. The court rejected this

argument on the basis that it would be unreasonable to require the plaintiffto do ~ 0 . ' ~

The respondents also argued that there was no evidential gap in the sense of McGhee because al1

the appellants had to do to determine the actual cause of the sùiking was to raise the ship. I t is tme

that in the case at bar the evidence might in this sense have been available: it was not beyond the

present state of science as in McGhee or blasted into pieces as in Nowsco. However the appellants

argue that it was a virîuaI impossibility for them CO bridge the evidential gap. The market value of

the Normac had been estimated at W50.000 ... Estimates for raising and refloating the ship .-. ranged fiom â324,OOO to $890,000. ... The economic cost of bridging the evidential gap appears

to me to be so completeIy disproportionate as to be impracticai ... It would not seem just for the

Courts to impose on the appellants an expense of the scale required to establish factuaI causality.

A Situation of linpossibifity - Wliat if is Not

We can also use this broad definition for cases involvïng a situation of impossibility to

distinguish those cases from others with which they might be compared. There are two

possibilities in this regard; other cases where a plaintiff fails in her claim because she is

unable to establish a causal relation, and other cases where on the evidence before the

court it is impossible to establish a causal relation. The first of these possibilities is

considered under the 'burden of proof, and the second in the context of the doctrine of

'spoliation of evidence' .

(1988) 44 C.C.L.T. 69 (F.C.A-) Fereinafter Lernik].

" Ibid at 96 pet MacGuigan J.

Part III- A Situation of impossibility

The Burden of Proof and the FaiZwe to Prove Causation

Cases involving a situation of impossibility can be distiaguished fiom the usud case

where a plaintiff fails in her claim because she is unable to prove the existence of a causal

retation. This is an important distinction to make because there are many reasons why a

plaintiff may fail to prove causation, and in the majority of them we see no objection to

the plaïntiff s claim failing as a result. For example, it may be that the defendant did not

in fact cause the plaintirs injury. Cases involving a situation of impossibility are just

one example of such a situation. They are the rare case where the burden of proof û d y

operates as a 'tie-breaker'.53

It wiI1 be suggested that in considering the different ways a plaintiff can fail to prove

causation, there are three possibilities;

(a) there is sufflcient evidence to determine causation, and the court determines

the issue against the p lah t ic

(b) there is insufficient evidence to detennine causation, and M e r evidence is

possibly available;

(c) there is insufficient evidence to detemine causation, and no further evidence

is available.

53 It appears that few cases are resolved purely by the operation of the burden of proof. Reson to the standard is necessary only in cases where there is doubt as to the matter at issue. "But the onus as a determining factor of the whole case can onIy anse if the tribunal fin& the evidence pro and con so evenIy balanced that it can corne to no such conclusion. Then the onus will determine the matter. But if the tribunal, after hearing and weighing the evidence, cornes to a determinate conclusion, the onus has nothing to do with it, and need not be fiirther considered." Robins v. Narionul Tmr Co. [1927] A C 5 15 (P.C.) at 520 per Lord Dunedin. See also S. Wexler & j. Efion, "Burden of Proof and Cause of Action" (1984) 29 McGiII L. J. 468 at 468 - 469.

Part III- A Situation o f Impossibiiity

(a) Suflcient Evidence tu Determine Causafion

In the majority of cases where a plaintiff s claim fâils because she is unable to prove a

causal relation, there is sufficient evidence before the court for a finding of fact to be

made on the issue. The problem here is not one of evidentiai uncertainty, as in a case

involving a situation of impossibility, but rather that the court has determined that the

plaintiff s injury was not caused by any negligent act of the defendant.

If we consider this situation M e r we c m see that there are in theory two possible ways

that a plaintiff may fair in this regard. Firsti the evidence may show that the injury to the

plaintiff was not a wrongful injwy. An example of this is the decision of the H o u e of

Lords in Mc Williams v. Sir William Arrol & ~ o m ~ a n y . " In that case, the deceased was

employed by the plaintiff as a steel erector in comection with the construction of a tower

crane. During the fmal stages of construction. he fell from the tower on which he was

working and was killed. At the time of the accident he was not wearing a safety belt,

which the evidence suggested would have saved hiru from the fdl. Safety belts had k e n

available until 2 days prior to the accident, when the defendant had moved them to a

different site. However, &er considering the evidence, the court held that if such a belt

were available, the deceased wouid not have wom it. Accordingly the plaintiff s claim

failed. The legally relevant cause of the injury was not the failure to provide a safety

belt, but the deceased's reluctance to Wear such a belt. The injury that was suffered was

accordingly not a wronghil injury''

A second possibility is that whiie the evidence rnay show that the injury to the plaintiff

was a wrongfùi injury, it rnay also show that the defendant was not the cause of that

wrongful injury. A good illustration of this possibility is the decision in Bindex Minepex

v. ~arnes . '~ In that case the plaintiff had been exposed to asbestos by a number of

" [1962] W.L.R 295 (H.L.). See also Kay v. Ayrshire, supra note 17.

s5 This illustrates the point made earlier that an important hnction of proof o f a causal relation is to identify the injury suffered by the plaintiff as a wrongtùl injury. See supra notes 42 to 45 and accompanying text.

s6 (29 July 1997 NSW Lexis 946) (C.A.)

Part III- A Situation oflmpossibility 24

defendants over the course of his working life. As a result be developed rnesothelioma

By far the greatest and most dangerous exposure to asbestos had been while he worked

for the Royal Navy, however a claim against it was barred by particular limitation

provisions. His claim was brought against the manufacturers of brake linings, which

contained asbestos, which he had been exposed to during his work at a garage. His claim

failed because while the court accepted that he had clearly suffered his injury as a result

of a tort, it was more likely one committed by the Royal Navy than by the parties before

the court.

The important point to note is that these cases are not resotved according to the incidence

of the burden of proof. The plaintiff is unable to satisfy the causal relation because no

such relation as a matter of fact exists. By contrast, in cases involving a situation of

impossibility there rem- the possibility that such a causal relation does exist.

fi) Insuficienf Evidence tu Determine Causal Relation - Furrher Evidence Amilable

A second, and more difficult, group of cases concern situations where a plaintiff fails to

prove a causal relation because there is insufficient evidence before the court to

determine the issue, but there is in theory at least the possibility of further evidence

having been offered by the plaintiff- The exact basis on which these cases are determined

is unclear. There is some similarity with the idea of spoliation of evidence that is

considered later." However, rather than an intentional interference with evidence, as is

involved in those cases, the standard here is closer to one of negligence. These cases

seem to be resolved on the ba is of the incidence of the burden of proof, and an

obligation on the party canying the burden to adduce sufficient evidence to discharge that

burden. The courts consider and recognise the possibility of M e r evidence king

available which the plaintiff has simply failed to produce, and it is on this basis that the

claim of the plaintiff fails.

57 See infra notes 63 to 74 and accompanying text.

An example of this type of case is Reed v. E I I ~ S . ~ ~ The plaint= worked for the defendant

as a jeweilery polisher. M e r leaving their employment he was diagnosed as suiTering

fiom tuberculosis. He alleged that this was caused by the defendant not taking proper

steps to remove fiimes and dust he was exposed to as a result of his working conditions,

and that this lowered his resistance to diseases such as the tuberculosis fiom which he

sufEered. However, the plaintiff called no evidence to support the drawing of any link

between the lowering of his vitaiity and the contraction of the tuberculosis. Ln these

circumstances the court was not prepared to speculate as to such a causal c o ~ e c t i o n

where the plaintiE could have brought f o m d more evidence on the issue. "[Tlhere

rnay be cases in which proof may be impossible. and this rnay be one of them. or may be

one in which complete proof would show no cause of action- However that may be, it is

quite certain that the plaintiff might have given much more evidence than was adduced in

his behalf on this question."59

The rationale for the decision seems to be that the plaintiff has a duty to bring forward al1

relevant evidence to support its c l a h (as an incidence of the bwden of proof). There was

insufficient evidence to suggest the existence of a causal relation, yet the plaintiff couid

have brought forward more evidence to resolve this uncertainty. Again, these cases c m

be distinguished fiom cases involving a situation of impossibility because in the later

group of cases, as we will see, it is impossible for either party to cal1 M e r evidence to

help resolve the issue.

(c) Insutcient Evidence to Determine Causation - No Further Evidence Available

The most difficult cases are those where the court is unable to determine on the evidence

whether the plaintiffs injury was caused by the negligence of the defendant, and no

58 (19 16) 32 D.L.R 592 (Ont. CA,). For other examples of cases where the plaintiff fails to bring forward sufficient evidence to establish her daim, and where the possibility existed for fiirther relevant evidence, see Levesque v. Corneau, supra note 1 ; Kaufmann v. Toronlo Ti-arsit CommlSSion ( 1959) 1 8 D.L.R (2d.) 204 (Ont, C.A.); Hoag v. MarshaU (1989) 39 B.C.L.R. 205 (B.C.C.A.); Roncato V. Caverly (1991) 84 D.L.R. (49 303 (0nt.C.A.).

Part III- A Situation of Impossibility 26

further evidence exists which could assist the court in this determination. These cases,

subject to the exclusion of cases involving the spoliation of evideme. are cases that

involve a situation of impossibility. Because a causal relation has k e n neither proved

nor disproved, the cases must be resolved according to the incidence of the burden of

proof. They are rare, because courts are reluctant to decide cases on such a standard.60

Examples 2 and 3, referred to in the introduction, were examples of such cases. One

m e r example may assist at this point to ernphasise the contrast with the groups of cases

just discussed.

In Wakelin v. London & South Western Raihvuy ca6' the body of the plaintiff s husband

was found lying near a pedestnan crossing for the defendant's railway line. It was

apparent that he had been stmck by a train. and indeed this was admitted by the

defendant. However, little more was known of the circumstances of the accident. While

the House of Lords was prepared to infer negligence on the part of the defendant, it was

not prepared to infer that its negligence caused the collision. The facts were equally

consistent with the deceased having been himself negligetd2

The evidence goes no M e r . It affords ample material for conjecturing that death may possibly

have been occasioned by that negligence, but it fùrnishes no data fiom which an inference can be

reasonably drawn that as a rnatter of fact it was so occasioned.

There is no suggestion in the decision that the plaintiff could have called further evidence

to resolve this uncertainty. Indeed, with the plaintiff s most helpw witness having been

kiiled in the accident, it is difficult to imagine what fuaher evidence could have k e n

called. However, in spite of this problem, the court was not prepared to speculate as to

"NO judge likes to decide cases on the burden of prwf if he c m legitimately avoid having to do so. There are cases, however, on which owing to the unsatisfactory state of the evidence, or othenvise, deciding on the burden of proof is the only just cause open to him to take." Rhesa Shbping Co. S.A. v. Edmunds, supra note 1 1 at 7 18 per Lord Brandon.

6' (1886) 12 App. Cas. 41 (H.L.) [hereinafier Wakefin].

62 Ibid. at 49 per Lord Watson.

Part III- A Situation of lmpossibility 27

the cause and hold the defendant liable for an accident that may well not have been its

fault .

The case illustrates the dificulties involved in a case involving a situation of

irnpossibility. The plaintiffs claim does not fail because there is no causal relation, as it

remains a possibility that such a relation does exist. Nor can it be said that the plaintiff

should have produced M e r evidence, as none was available. In these cases. liability is

determined simply on the basis of the incidence of the burden of proof.

The Spoliation of Evidence

The second group of cases fiom which cases involving a situation of impossibility must

be distinguished are cases where a party to the litigation has destroyed or deliberately

fails to produce evidence that might help resolve the issue in dispute. In these cases the

evidence exists, or existed, but because of the deiiberate act of one of the parties to the

litigation, that evidence is not brought before the court* ïhese cases are covered by the

doctrine of spoliation of evidence, and they are resolved by the court drawing an adverse

iderence of fact against the person responsible for the evidential deficiency.

It is a d e of long standing that if a party to litigation destroys or intentionally fails to

produce evidence relevant to the matters in dispute. an adverse inference may be drawn

against them that the evidence was unfavourable to their case.63 This process of

inference drawing is capiured in the rnaxim. omnia praesumunrur contra ~ ~ o l i a t o r e m . ~

63 See generally, J. S. Gorelick, S Marzen, & L. Solum, Destruction of Evidence, (New York: Wiley Law Publication, 1989); 1. D. Lawson, The Law of Prmmprive Evidence, Z~ ed. (St Louis: Central Law Journal Company, 1899) Chapter 8; H. Broom, A Selecrion of Legal iMmirns, Cfass$ed and Ifhstrated. 8' Amer. ed. (Phiiadelphia: TI & J. W. Johnson & Co., 1882) at 938 - 942; J, M. Maguire & R- C. Vincent, "Admissions Iniplied from Spoliation or Related Conduct" (1935) 45 Yale L. J. 226; L. Solum & S. Marzen, "Truth and Uncertanity: Legal Control of the Destruction of Evidence" (1987) 36 Ernory L. J. 1085.

" "All things are presumed against a wrongdoei'. J. Burke ed., Jowitt 's Dicfionary of Engfish Law, 2& ed (London: Sweet & Maxwell, 1977) at 1283.

Part III- A Situation of hpossibitity 28

The leading case is Annory v. ela ami rie.^^ In that case, the plaintiff chimney sweep took

a jewel to the defendant for valuation. While the defendant's apprentice was weighing

the jewel, the stones were removed, When the jewel was returned to the plaintiff the

stones were missing and the ptaintiff brought an action in conversion for the return of the

stones. At triai the defendant did not produce the stones, and so it was impossibie to

know the value of them. The court accordingly inferred that they were stones of the

highest value.

The basis on which this inference is drawn has been the subject of some debate?

However, it seems clear that the dominant basis on which the inference is understood is

that the destruction of evidence, or the refisal to produce evidence, betrays a guilty mind,

in that had the evidence been favourable to the spoliator, it wouid have been preserved or

produced. An example of this is the decision in The North British Mercantile Insurance

Co. v. ~ o u r v i l l e . ~ ~ The case concerned the fraudulent over-valuation of a property for an

insurance claim. The circurnstantial evidence strongly suggested such an over-valuation,

but the only records that would property explain the true value of the property had been

destroyed by the insured after proceedings had been c~rnmenced.~~

65 (1 722) 1 Str. 505. See also R v. A d e l 1 Hob. 109: CIunes v. Pe-ey (1807) 1 Camp. 7; Baker v. F d o n g [1891] 2 Ch. 172.

66 The basis of the inference that is presented here is the one generally accepted by the courts. I t aIso explains most of the Iimits in the application of the doctrine that are also discussed. However. it has been suggested that this is too narrow a conception of the hnction of the doctrine, focusing only on the idea of achieving accuracy in court proceedings. SoIum & Marzen argue that courts also consider the functions of compensation to the victim of the spoiled evidence, and punishment of the spoliator. Supra note 63 at 1 160 - 1 177. The importance of these fiinctions would help explain cases such as Gray v. Haig (1 855) 13 Beav. 65; The Opheiia [1916] A.C. 206 (P.C.); and CVardour v. Berisford (1687) 1 Vern. 452 where the destruction of evidence did not as a rnatter of fact. as opposed to presumption by the court. seem to betray a guilty rnind.

67 (1 895) 25 S.C.R 177 (S.C.C.), See also Roe v. Harvey ( 1 769) 4 Burr. 2485; Chiidrem v- Sarby (1683) 1 Vem. 207; James v. Biou (I826) 2 Sim. & St. 600; The King v. Cholpeck Fish Company (1913) 17 6.C.R 50 (B.C.CA).

68 Ibid. at 190 per Taschereau J. Macguire & Vincent trace this logical relation through what they describe as a "well-know formula: The litigant's conduct indicates a beIief relevant and detrimental to some feature of his case; therefore he holds that belief; therefore his case in this regard is defective." Supra note 63 at 235.

Part III- A Simon of Impossibi Iity 29

The rule omnia prummunrur conrra spoliatorem is one based on common sense and reason. If

these pape= had supported the claim, they woutd have been scmpulously taken care of, and their

non-production justifies us, in law, to come to the conclusion that they wouId, if forthcoming, be

adverse to the respondent's contentions.

On this view, the evidential gap created by the misshg evidence is addressed by an

inference as to the hue state of affai~s.~~ It remains an inquky into the fact at issue, and

the drawing of the inference has the effect of describing how matters in fact were. This

approach is supported by the requirement referred to in many cases that there must be

intentional wrongdoing in the destruction of evidence;' the importance of the timing of

the destruction (in that it should be done in contemplation of ~iti~ation)." that the

inference cannot be drawn if known facts tend IO contradict it. that the inference cannot

be drawn unless some basis at least exists as to its t r ~ t h , ~ and that the spoliator is able to

rebut any presumption of a guilty mind in destroying or failing to produce the evidence."

In surnmary, "the courts require an adequate showing of a rational comection between

the withholding of evidence and the conclusion of guilt or c ~ l ~ a b i l i t ~ . " ~ ~

Therefore it can be seen that seen that in such cases the evidential gap that is created by

the destruction of evidence is resolved by an inference of guilt against the spoliator.

These cases c m again be distinguished fiom cases involving a situation of impossibility.

First because in cases of spoliation, evidence that may have helped resolve the issue at

69 "As its name suggests, the spotiation inference is a logical deduction of guilt fiom the destruction of presumabty incriminating evidence." Gorelick, supra note 63 at 5.

70 For example, Delan- v. Tenkon (I758) 3 Brown 659; H. & C. Smith v. Great Western Railway Company [192 11 2 K.B. 277 (C.A.); [ndian Oil Corporation v. Greenstone Shbping SA. (Panama) Cl9883 1 Q.B. 345; Dobson v. North Tynside H.A. [1996] 4 ALI E.R 474 (C.A.); Hoescht v. Celanese v. B.P. Chernicals [1998] F,S.R 586. See also Macguire & Vincent, supra note 63 at 23 1 - 235 for a discussion of the importance of this requirement.

" Gorelick, supra note 63 at 43-

" Smirh v. LW (1873) 15 N.B.R. 64 (C.A.); Cowper v. Earl Cowper (1 734) 2 P. Wms. 720.

For example, WiIIiamson v. Rover Q d e Co. [ 1 90 1 j 2 Q.B.D. 6 1 5 (C.A.) at 6 19 per Fitz Gibbon L.I; St- Louis v. The Queen (1 896) 25 S.C.R. 649 (S.C.C.).

'' Maguire & Vincent, supra note 63 at 234.

Part III- A Situation of Impossibility 30

sorne point existed (and possMy stilt does). Second, there is a clear b a i s on which one

of the parties to the litigation can be blamed for this evidential deficiency. Neither of

these possibiiities seem to apply to cases involving a situation o f impossibility

PART IV - A STRUCTURE FOR CASE LAW

In the previous Part, we considered in general t ems the sort of case that involves a

situation of impossibility, and distinguished it from other instances where a plaintiff fails

to prove causation, or it is impossible on the evidence before the court to establish

causation. We now examine specific examples of cases involving a situation of

impossibility. This Part is divided broadly into two sections. In the first. a general

structure for anaiysing the cases will be suggested. This structure is denved fiom the

interaction of two variables; the degree of uncertainty of a causal relation between the act

of the defendant and the injury to the plaintiff, and whether the competing causes are

tortious or non-culpable. The structure that is suggested is ultimately one that is

descriptive of the case law. However. it also represents a logical and systematic

organisation of the case law that helps us recognise the movement fiom one category to

the next as a movement from a situation of greatest certainty of causation to a situation of

least certainty.

In the second section we consider examples of cases within each of the categories

suggested by this structure. In doing so we identiQ the different features of these cases .

that may explain why it is that they are often treated differently to other cases where a

plaintiff is unable to establish a causal relation. It will be suggested that there are four

explanatiow that arise fiom the review: the possibility of a 'guilty' defendant escaping

liability (a concern that is sometimes expressed in t e m s of the potential for an

unenforceable duty), fault on the part of the defendant in creathg or at least foreseeing

the situation of impossibility, the possibility that a plaintiff who has suffered a wrongful

injury will not be compensated (or occasionally that a defendant who has inflicted a

wrongfd injury will not be required to compensate), and the extent to which the causal

relation c m still be vindicated in face of the situation of impossibility.

Part IV - A Stnictuce for the Case Law

The Dynum*cs of a Structure

In this section an attempt is made to ideni@ a structure for considering cases involving a

situation of impossibility. It will be suggested that there are two main principles that c m

assist us in organising the cases. The first is concerned with the degree of uncertainty of

the existence of a causal relation that is created by the situation of impossibility. The

second relates to whether the competing causes are tortious or non-culpable.

The basis of this structure reflects what it is that we know about the cause of the injury to

the plaintiff. It asks two questions; what do we know about the defendant's act as a

cause? and what do we know about the other possible causes. While this structure is

intended to be descriptive of the cases, it also reftects a progression fiom the situation of

greatest certainty in our knowledge of causation to a situation of greatest uncertainty.

This seems clear fiom the fmt principle of the differhg degrees of certainty of causation.

Where a plaintiff cm show that her injury was to some extent at least caused by the

negligent act of the defendant, the nature of the evidential uncertainty is less than where it

is impossible for the plaintiff to show any causal relation. Likewise where the plaintiff is

able to show the possibility of some causal relation, the degree of certainty is greater than

where that relation is purely speculative. Yet the same progression c m be seen in the

nature of the competing cause. If a plaintiff is able to show al1 causes are tortious, she

can also show that she has been the victim of a tort. In effect, she can show she has

suffered a wrongful injury. Here we know more about the cause of her injury, in the

context of her entitlement to compensation. than we do if it is still possible that her injury

was the result of a non-culpable act.

However the uses that can be made of this structure are iimited, It is intended only as a

convenient way of organising the cases which reflects our knowledge of the causes and

highlights the difKerent way courts treat competing tortious and non-culpable causes. It

does not explain why such a structure need even exist, nor why cases within different

categories of the structure may be resolved differently. Ultimately we will see that the

Part IV - A Stmctute for the Case Law 32

division between cases where there is a substantial possibility of a causal relation and

cases where such a relation is only speculative reflects cases where a plaintiff succeeds in

her claim and those where she fails. Once that argument is made the structure can be

reduced simply to a categorisation of cases according to the degree of uncertainty of a

causal relation between the injury to the plaintiff and the negligent act of the defendant,

with the fact of competing tortious causes being considered as one of many broad policy

considerations that may arise in any particular case. Wowever at this stage. where we are

simply examining the different possible cases that may arise, it is convenient to maintain

the distinction between cases where there are competing tortious causes and those where

the competing causes are non-culpable.

Degrees of Uncertainiy

In any case where it is impossible to prove causation, the result is that while the

possibility of a causal relation exists (and so also its converse of a lack of a causal

relation) whether that possibility was fblfilled remains uncertain. However, this

uncertainty is not categorical. Simply because a plaintiff cannot satisfi the legal test for

causation does not mean that the possibility of such a relation is constant in al1 cases.

Rather, given the variable nature of evidence that rnay be produced in any one case, the

strength of a possibility of a causal relation may also Vary.

If we consider the position of a plaintiff where it is impossible to prove causation, it

would seem that there are broadly three different situations that may arise.

(a) The piaintiff may be able to show that the defendant's negligent act

contributed to the injury, but it is impossible to show the extent of that

contribution. Regardless of this irnpossibility, however, the plaintiff is able

to show that the defendant's negligent act was more probably than not the

legaily relevant cause of her injury. ("Certainty as to contribution and cause").

Part IV - A Structure for the Case Law 3 3

(b) As with the first situation, the plaintiff rnay be able to show that the

defendant's negligent act contributed to her injury, but it is again impossible

to show the extent of that contribution, Here, however, it is also impossible to

show that the defendant's negligent act was more probably than not the cause

of the injury. ("Certainty as to contribution, uncertainty as to cause").

(c) A third possibility is that the plaintiff may be unabie to show any causal

connection between the defendant'ç negligent act and her injury. m a t is, in

contrast to the two earlier situations, there is no proof of a causal relation at

ail, ("Uncertainty as to cause'?.

The first of these situations does not present any problem for a plaintiff. As was noted in

Part II, courts do not demand complete certainty of the fact of causation, nor indeed of

any fact. Al1 that is required is that the plaintiff prove that the injury was more likely

than not caused by the defendant's negligent act. If this is established then the fact is

regarded as conclusively proved, even though the exact proportion of the contribution is

~nknown.~' Even if we were to give the defendant the benefit of the unknown causal

possibility (i.e., assume it in her favour) it would not othenvise effect her liability.

The final two possibiiities do, however. raise issues as to how the problem of

impossibility is to be dealt with, primarily because if we again assume the causal

possibility in favour of the plaintiff, it may be that the defendant's negligent act was

causaily unrelated to the injury she suffered, I f liability were imposed on a de fendant in

such circumstances, it may be that liability was imposed on an otherwise innocent

It is these two possibilities that create the problem for the plaintiff of an

impossibility of proving causation.

75 See discussion supra notes 37 to 4 1 and accompanying text.

76 In this paper the reference to 'innocent' and 'guilty' defendants refers only to whether that defendant did or did not 'cause' the injury.

Part IV - A Stnichut for the Case Law 34

Yet an important distinction must be made between the two situations. Where we know

that the defendant's negligent act contributed at least to the injury, we know that it played

some causative role. There is a clear causal relation of some sort. The negligent act of

the defendant was at least a cause of the plaintiff s injury. The question is whether it was

either sufficient or necessq to have caused the injury. Indeed the prevailing view is that

such cases do not in themselves present a problem of establishg cause in fact. although

they clearly present a problem of detennining the extent to which the defendant should be

Iiable for the consequences of her action." By contrast where it is impossible to show

whether a defendant's negligent act even contributed to the injury. there is no proof of a

causal relation in any form. Therefore. at a minimum, cases where there is at least

certainty of contribution suggest a greater cenainty of causation than those where no

contribution can be s h o w at dl.

Analysis of the case Law dso suggests that a refinement of cases involving a situation of

uncertainty as to cause can be made. In these casesT a distinction appears to be drawn

between cases where the presence of a causal relation between the negligent act of the

defendant and the injury to the plaintiff rernains a substantial possibility, and those cases

where such a causal relation seems pure speculation. The exact nature of this division is

dificuit to articulate, although it would seem to be grounded in common sense notions of

cause. Yet it emerges as an important distinction in the case law. and some atternpt will

be made here to articulate its basis before proceeding fürther.

The first way of conceptualising this division is simply to consider the process of proof in

court proceeduigs. Certainty in judicial proceeding is a relative concept. The evidence

before the court is often imperfect. The more evidence produced tending towards the

alleged fact, the greater the degree of certainty. The less evidence, the less certainty. The

different degrees to which a court can be certain of a result are reflected in the different

standards of proof that can be used; beyond reasonable doubt in criminal matters, and the

balance of probabilities in civil matters (although this standard can itself be raised if the

-

" See W r i g h ~ supra note 26 at 1974.

Part IV - A Structure for the Case Law 35

alleged fact is a serious one such as h;i~d). '~ The same applies when a fact is unproven,

and is only a possibility, as is the case where there is a situation of impossibility. It is a

question of degxee. A court may in one case treat the existence of such a relation as a

matter purely of speculation, whilst in another it rernains a substantive possibility, dbeit

one that cannot ultimately be re~olved-'~

This idea of diffierent degrees of uncertainty of causation is also expressed in the case law

in two different ways. The first is in the idea of the creation of a risk by the defendant,

and an injury to the plaintiff within the scope of that risk While this doctrine has

sometimes been suggested as an alternative to causation as a means of comecting a

plaintiff s injury to the defendant's negligent act." one of its attractions is that it reflects

an intuition of the possibility of a causal relation. Proof that a defendant created a risk of

injury, and that the plaintiff has suffered an injury within the scope of that risk, is not

78 See generally R. Pattenden. "The Risk of Non-Persuasion in Civil Trials: The Case Against a Floating Standard of Proof" (1988) 7 Civil Sust. Q. 220; Harner. "The Civil Standard of Proof Uncertainty: Probability, Belief and Justice", supra note 39.

79 A similar argument, considering the degrees of persuasion a court can have of an alleged fact. has been made by Professor Carpenter in considering what is required to submit a disputed matter to a trier of fact. In most commonwealth jurisdictions, where in civil trials at least the fùnction of determining questions of fact is also performed by the judge. this distinction is not so important. However, in those jurisdictions which retain jury trials for civit matters, the distinction has some importance as it determines when as a matter of Iaw, a piaintiffs claim should be dismissed, or a verdict directed, He suggests that there are a number of different degrees of conviction a court can have about a fact in issue.

"If the degrees of probability of the existence of a fact were arranged in order fiom the least to the greatest, it might form a hierarchy something Iike this: (1) Clearly not a cause. (2) Possible but very improbable that it was a cause. (3) Reasonably was a cause but probably was not. (4) More Iikely that it was a cause than that it was not. (5) Reasonable possibility that it was not a cause but probably was. (7) Possible but very improbable that it was not a cause. (8) Clearly a cause, For the plaintiff to prove the existence of a fact, he does not have to prove to an absolute certainty that the defendant's act rather than some other cause w s responsible for the damage. If it was ( 1 ) clearly not a cause, or (2) possible but very improbable that it was a cause, the court should non-suit the plaintiff, or direct a verdict for the defendant. If it was (7) possible but very improbable that it was not a cause in a civil action, or (8) clearly was a cause in either a civil or criminal action, the court should direct a verdict for the plaintiff if al1 the other elernents of legal liability are found to exist- If it appears to fa11 into (3), (4)- (5). or (6) in the hierarchy given, the q~cstion should be feft tothejwy ..."

See C. E. Carpenter, "Workable Rules for Determining Proximate Cause" (193 1) 20 CaIif. L- Rev. 396 at 399.

80 See, for exampie, the argument made by Gerecke, supro note 6.

Part IV - A Stntcture for the Case Law 36

proof of a causai connection,*' but where we will never know whether such a relation

exists, it is a useful way to conceptualise the remaining possibility of such a relation. The

extent to which it will suggest such a relation m u t depend on the existence and number

of other possible sources of the risk. But where the number of those competing sources is

limited, the idea of an injury within the scope of the risk seems to suggest a substantive

possibility of a causal relation-

The idea of injury within risk reflects an evaluative approach to the issue of causation.

Yet in some cases, evaluative considerations that may assist the court in establishing

causation are absent, yet their stifl remains a statistical basis on which it coutd be said

that a substantial possibiiity of a causal relation e~ i s t s . ' ~ In these cases the possibility of

a causal relation is established by considering the simple probability of such a relation.

Where the possibility of a causal relation is an alternative between a nurnber of causes,

the probability of any one cause being the cause can be stated in percentage tenns. For

exarnple, the probability of a causai reiation may be 50%, 30%, or less. Clearly as the

probability of a causal relation decreases. the extent to which it can be described as a

substantial possibility is also diminished. However, where it is suficiently high, it is

clear the courts have used the existence of a pure statisical chance of a causal relation as

the ba i s for concluding that the is a substantial possibiIity of such a relation.

Accordingly the degree of uncertainty created by a situation of impossibility can be

categorised in three ways; certainty as to contribution (although the extent of that

contribution is unknown), uncertainty as to cause but there is a substantial possibility of a

81 See Weinni, supra note 25 at 523; Gerecke, supra note 6 at 828.

82 ï h e distinction between statistical probabilities and an evaluative approach to the evidence of causation is not often clear. The courts have consistently affirmed that they are not bound by a statistical assessrnent of the probabilities of a result See the discussion supra notes 20 to 22 and 37 to 4 1 and accompanying text. A good exarnple of the difference that cm exist between a statistical possibiiity and an evaluative approach to causation is provided by Gonthier J. in Lafrriere v. Lawson. supra note 40 at 657: "If one moves then to a procedure which is recomrnended despite a mere 25 % chance of success according to expert evidence, it is still not a foregone conclusion that the doctor's fault in not using this procedure must be said to have no causal role in the patient's death or sickness. If the experts are examined properly, a judge may well find that he or she is justified in concluding that the omission of that procedure did not cause the death or sickness, but that it caused other Iesser but clearly negative results (e-g., slightly shoner Iife, greater pain)."

Part IV - A Structure for the Case Law 37

causal relation, and uncertainty as to cause where the possibility of a causal relation is

speculative.

Tortious and Non-Culpable Cornpethg Causes

The second principle that is relevant in identiQing a structure within which to consider

these cases concems the nature of the competing causes; whether they are in the

aggregate tortious or non-culpable. This division is important for understanding the

substantial aiiowauces that are ofien made in favour of a piaintiff confionted by a

situation of impossibility. It is ctear that the courts treat cases where competing causes

are tortious differently fiom those cases where the competing causes are non-cuipable.

The law in this area could be described as somewhat c o h e d , however the position can

be summarised as follows." Where the competition is between a tortious wrong, and a

sufficient non-cuipable wrong, the defendant will not be liable. Where the competition is

between different tortious wrongs, however, if the respective contributions to the injury

cannot be segregated, each defendant will be liable for the whole of the loss to the

phintiff.

The basis of this distinction appears to corne from the nature of loss in tort law." What

constitutes a loss in tort law must be defined according to some constant, which is the

situation of the plaintiff without any tortious injury. The non-cdpable cause forms part

of the background against which the plaintiff s position is to be evaluated, and as such the

defendant's negligent act does not cause any loss if another non-culpable cause wouid

have caused it. However, the constant against which the defendant's negligent act is to

be considered is more accurately described as that of a plaintiff without any wrongs,

including other tortious wrongs. Therefore where there is a competition between tortious

83 This summary is taken largly from the review in Cooper-Stephensen, supm note 16 at 786 - 806. See also G . Williams, "Causation in the Law" [l96 11 C.LL 62 at 76; R 3. Peaslee, "Multiple Causation and Damage" (1934) Harv. L. J. 1127; the dissenting opinion o f MacLaughlin J in Sunrise Co. v. The "Lake Winnipeg" (I991), 77 D.L.R 701 (S.C.C.); Penner v. Mi1chell[1978] 5 W.W.R 328 at 332 - 336 (Alta. C.A.); Bakr v. WiIIoughby [ 19701 A C 467 (H.L.).

84 Cooper-Stephensen, supra note 16 at 786 - 806.

Part CV - A Structure for the Case Law 38

wrongs, the defendant's conduct is to be measured against a plaintiff who has not

suffered any wrong, and the defendant rnust accordingly compensate the plaintiff in fiill.

The different treatment these czses receive can probably only be justified in terms of

policy rather than 10~ic. '~ Where the competing causes are non-culpable. to compensate

a plaintiff would be to place her in a better position than she would othenvise have ken-

However, where the competing causes are tortious, not to compensate her would be to put

the plaintiff to the chance of falling between the *'two stools" of the tortious defendand6

Where a plaintiff is able to show that a11 the competing causes are tortious. she will also

necessarily have shown that the injury she has suffered is a wrongfùl injury. She will

have shown herself entitled to compensation. as opposed to a plaintiff who rnay not even

have suffered an injury recognised by tort law. Therefore, this division between the

nature of the competing causes also reflects a division between certainty and uncertainty

as to tortious (Le. wrongful) inju~y.~'

A Structure for the Case Law

Combining these two broad principles suggests the following structure for cases where it

is impossible to prove causation.

85 Peaselee, supra note 83 at 1 13 I .

86 b b I n ~ ~ f a r as their accountability to the plaintiff is concerned, it is manifestly just that he should not be put to nice discrimination; both defendants being offenders against the plaintiff, and the result caused k i n g more or less the product of their united wrong, he shoufd not be called upon to act as a divider between thern. Nor should he be put to the chance of falling between two stools." Peaselee, supra note 83 at 1 132.

Part IV - A Structure for the Case Law 39

Catego ty I

Certainty as to Contribution

Competing Tortious Causes

Exarnple: Corey v- Havener

Category 3

Uncertainty as to Cause - Substantial Possibility of

a Causal Relation

Competing Tortious Causes

Exarnple: Cook v. Lewis

Ca tego ry 5

Uncertainty as to Cause - Speculative Causal

Relation

Competing Tortious Causes

ExampIe: Sindell v- Abbott Laboratories

Category 2

Certainty as to Contribution

Corn peting Non-Culpable Causes

Example: Bonnington Costings v. Wurdlav l

Category 4

Uncertainty as to Cause - SubstantiaI PossibiIity of a

Causal Relation

Corn peting Non-CulpabIe Causes

Exarnp le: McGhee v. Afutiod Coai Board

Category 6

Uncertainty as to Cause - SpecuIative Causal

Relation

Competing Non-Culpable Causes

Exarnple: Wilsher v. Essex A . H A

Category I - Certainîy as to Contribution - Cornpethg Tortious Causes

This fust situation we consider is where there is certainty of contribution by the

defendant to the plaint i rs injury, and the competing causes are also tortious acts. This

situation is illustrated by the decision in Corey v. ~avener.'~ The facts of the case are

well known. nie plaintiff was riding his carriage on the highway. The defendant's were

behind him, both riding motorcycles that made a loud noise and emitted smoke. They

passed on either side of the plaintiff at high speed. causing the plaintifYs horse to bolt

and in the process injuring the plaintiff. In the circumstances of the case "it was

impossible to determine what portion of the injury was caused by e a ~ h " . ~ ~ The jury,

however, concluded that each defendant conûibuted to the injury, and on appeal it was

held that this was mfTicient to make both Iiable for the whole of the injury caused-

" This division is also suggested by Peaslee, supra note 83 at 1 129.

88 (1 902) 65 N.E. 69 (Mass. SJ-C.). Other examples of cases in this category are McAfIister v. The Penmyfvania Raiiroad Company (1936) 324 Pa. 65: Barker v . Permanent Steamless Ffoors [ 19831 2 Qd- R 56 l (C.A.).

Part IV - A Structure for the Case Law 40

While the case is well known, it is not often seen in t e m s of the impossibility of proving

causation. The decision is treated by many writers as an exarnple of a cornpetition

between two sufficient, tortious causes of the i n j ~ r ~ . ~ * This approach assumes that it was

known that neither defendant's action was necessary to cause the injury, but both were

sufficient. The case is then treated as a paradigrnatic example of the failure of the 'but

for' test for causaion, as applying the test in such a case would lead to the 'absurd' r e d t

that each defendant would be able to say that 'but for' their act, the plaintiff would still

have suffered the injwy (and therefore avoid liability) even though the action of each was

clearly sufficient to have caused the injury?' It will be suggested that this approach

results fkom a mis-reading of the decision, and the case is properly seen as an example of

the irnpossibility of proving causation.

Contrary to what many writers assume. the decision makes no reference to the act of

either defendant being suficient to have caused the injury in the absence of the act of the

other.g2 The only reference to the sufficiency of either defendant's act is that it is

impossible to know the "portion of the i n j w " that was caused by each defendant. This

seems to leave open the possibility that both acts were necessary (the case could then be

resolved by the simple application of the 'but f o i test), that one act \ÿas sufficient and the

other neither sufficient nor necessary, or that both were sufficient but neither necessary.

The problem in the case was not simply that the application of the 'but for' test would

allow two defendants whose conduct was sufficient to have caused the injury to escape

liability, but rather in establishing the sufficiency or necessity of each defendant's a ~ t - ~ '

Once Corey v. Havener is seen in t ems of impossibility, the nature of the allowance

made in favour o f the plaintiff becomes clear. Under an interpretation that views the case

- - - - - - -

90 For example, Fleming, supra note 16 at 222; Keeton ed.. Prosser and Keaton on the Lmv of Torts, 5' ed. (St Paul, Minnesota: West Publishing Co., I984) at 266; Weinrib, supra note 25 at 520.

91 Ib id..

92 Malone, supra note 26 at 90; Wright supra note 26 at 179 1 - 92.

93 A bener example of a case of cornpeting sufiÏcient causes is the decision in Andersen v. Minneapolis St. P. & S. Ste. M. Ry., supra note 31.

Part IV - A Structure for the Casc Law 41

as a cornpetition between sufflcient causes, the plaintiff had proved al1 the elements of a

tort against each plaintiff. The court s h p l y sought to avoid what it saw as an absurd use

of the 'but for' test, which would have allowed al1 defendants to deny liability in

circumstances where at least one (and possibly both) of their acts were sufficient d o r

necessary to have caused the injury.

Yet when the case is seen as one involving a situation of impossibility, it is clear that (in

theory at least) a substantive allowance was made in favour of the plaiotiff.9' Had the

plaintiff been able to prove the proportion to which a particular defendant's act

contributed to the injury, and that act was itself sufficient to have caused it. he would

have been entided to full compensation fiom that defendant and it wodd not have been

necessary to hold liable a defendant whose negligent act may have been neither sufficient

nor necessary to have c a w d the injury (which is the possibility created by the decision).

The eEect of the decision is to render such a distinction irreievant. The plaintiff was not

required to prove whether the act of either defendant was sufEcient, or whether both of

the defendants acts were necessary. but rather the lesser standard of whether their acts

made a substantial contribution to the injury. The allowance that was made in favour of

the plaintiE was not in avoiding the absurd result created by the application of the 'but

for' test, but rather in lowenng the standard of proof required of the plaintiff so that the

bare minimum he was able to show was sufficient for the purposes of imposing liability.

Having identified the problem in Corey v. Hmrener as being one of irnpossibility of

proving causation, we can then consider the factors that may have motivated the court's

decision. Given the brevity of the decision. these factors are not manifest. However, it

will be suggested that the facts of the case raise three possible considerations that may

help explain the decision. Perhaps the ovemding consideration was that it kvas clear that

94 It seerns that a substantial allowance, at least in theory, is made in favour of the plaintiff in using the test of substantial possibility or material contribution to the injury. Malone describes it as follows, supra note 26 at 89: "in the combined force cases the courts do not abandon the effort to define cause. They merely re-establish the point o f acceptable affinity between misconduct and the loss lower on the scale-" See also the decisions in Bonnington Castings. supra note 17, and Nicholson v. Arfcrs Sreef Fou- and Engineering Co. Lrd Cl9571 f W.L,R 6 13 (H.L. (Sc.)). which descnbe the substantial factodmaterial contribution test as requiring only proof of a causal relation more than de minimus.

Part IV - A Stnacture for the Case Law 42

the plaintiff was the victim of a tortious wrong committed by at least one of the

defendants, and probably b t h . If the defendants were able to take advantage of the

situation of impossibility that confionted the plaintiff they would each be able to avoid

liability for a wrong to which both had clearly contributed, and for which the act of one

was at least either necessary or suscient to have caused the injury. Here the concern

was both that a deserving plaintiff would not be compensated, and that a negligent actor

would not be liable for an injury bis act very probably was sufficient to cause.

In addition, there seems a sense in which the impossibility that confionted the plaintiff

was the responsibility of the defendants. This is not made expiicit in the decision, but it

does seem to underlie the result. The problem of proof was the result of the two

motorcycles passing the plaintiff at the sarne time which rendered it in~possible to

establish the causative effect of each act. it could be said that even if there was an

'innocent' defendant, their negligent act still created the problem of proof for the

plaintiff. At the very least, the close retationship between the hvo defendants suggests

that the innocent defendant should have foreseen the possibility of such a problem of

pro0 f arising .

Underlying these two considerations is a recognition that there was a causal relation of

some kind between the negligent acts of the defendants and the injury to the plaintiff, in

that each defendant's act at least contribrrred to the injury. It was not that the defendant

possibly played no role in causing the injury to the plaintiff. Rather, he clearly played

some role, and the question was whether that was either ~ ~ c i e n t or necessary to have

caused the injury.

Caregory 2 - Certainty as to Contribution - Compefing Non-Culpabie Causes

The situation in Corey v. ffmener becomes more difficult if the competing causes are

non-culpable. In such a case, it is not ciear that the plaintiff has even suffered a wrongful

injury. If it could be shown that the competing non-culpable causes were sufficient to

cause the injury, then the defendant will not be liable even if its negligent act would also

Part IV - A Structure for the Case Law 43

have been sufEcient? Therefore if liability were imposed in such a situation of

irnpossibility, the court may be imposing liability on a defendant whose act may not have

caused the injury, to compensate a plaintiff who may not have M e r e d a wrongfùl injury.

An example of a court imposing liability in such a case is the decision of the House of

Lords in Bonningion Castings v. ~ a r d l a w . ~ ~ In that case, the pursuer worked in a

foundry owned by the defender. removing the sand coating fiom the outside of steel

castings. As a result of this work he developed pneurnoconiosis. This condition was

caused by inhaling the fine particles of silica dust that were created when the sand was

removed &om the casting. Within his work area there were three sources for this silica

dus& however only one of those sources resulted from negligence on the part of the

defender. The problem of impossibility in the case was that while it was clear that the

disease was caused by breathing the atmosphere containing the silica dust from al1 three

sources, it was impossible for the pursuer "to resolve the cornponents of that atmosphere

into particles caused by the fatilt of the defenders and particles not caused by the fault of

the defenders, as if they were separate and independent factors in his illne~s."~'

The House of Lords was unanhous in holding that regardless of the impossibility of

proving the proportion o f dust inhaled from the negligent source, the defender should be

liable for the full loss suEered by the pursuer. nie majority took a similar approach to

that in Corey v. Havener and opedy modified the standard of proof required for

causation in the case. On ùiis approach. the pursuer need only show that the dust fiom the

- -- - - - -- - - -

95 See discussion supra note 83 and accompanying text.

% Supra note 17. For other examples see Nicholson v. Atlas Steel r'oundry and Engineering Co. Lld. supra note 94; Vernon v. Bosley (No. 1) Cl9971 I Al1 E.R. 577 (C.A.). In a number of cases. while the extent of the contribution is unknown, the court has accepted that it is clear it did not contribute 100% to the total injury. In recognition of this the court has sou& to reduce the award of damages. See for example Deacon v, Heichert (1984) 9 D.L.R. ( 4 9 680 (B-CS-C); Thompson v. Smith Shiprepairers (North Shielak) Cl9841 1 Q.B. 405.

Part IV - A Stnicturr for the Case Law 44

negligent source "materially contributed" to the disease, a fact which was clearly

established on the medical e ~ i d e n c e . ~ ~

It is suggested that the case is again an example of a substantial allowance being made in

favour of a plaintiff confkonted with an impossibility of proving causation. To

understand the nature of this allowance, we need to consider the possible outcornes had it

been possible to prove causation. It could have been that the dust fiom the negligent

source and dust fiom the non-negligent source were both sufficient to cause the injury,

were both necessary to cause the injury, or that only one of them was sufficient and/or

necessary. This analysis can be M e r refïned because it is clear from d l the judgments

that by far the greater source of dust came from the non-culpable source, so that it does

not seem possible to say that the negligent source couid have been nifficient whüe the

non-culpabie source insufficient. If the non-culpable source had itself k e n sufticient to

cause the injury then it seerns clear that the defendant could not have been liable."

Accordingly, the only ba i s of liability for the defendant would be if it was shown that

both sources were necessary to cause the injury. In imposing liability on the defendant,

the House of Lords effectively assume this to have been the case- 100

Again, there is little discussion in the decision as to why this assumption was made in

favour of the pursuer. Yet it seems clear that the three broad factors we identified in

Corey v. Hmener were also present in this case. While the pursuer could not point to the

potential of falling between two torifeasors, as the plaintiff could in Corey v. Hmener, a

similar argument codd be made in respect of the potential for an unenforceable duty if

98 Lord Keith, on the other hand, focused on the exact injury suffered by the pursuer- In his view the facts supported the inference that without the addition of the d u t frorn the negligent source, the pursuer may not have developed the disease when he did, and possibly rnay not have devetoped it at alt. On his approach, the case was resolved simply on an application of the 'but for' test.

99 See discussion supra notes 87 to 86 and accompany ing text.

'O0 The unusual nature of the decision in this regard is noted by Professors Trindade and Cane. 'The curiosity of the principle is that a defendant can be held Iiable for the whole of a loss even though al1 that can be proved on the balance of probabilities is that he contributed to it. n e principle ailows the coutt sirnply to ignore the lack of evidence on the issue of which factor caused part of the plaintiffs loss." Trindade & Cane, supra note 16 at 451. Stapelton refers to it as a "radical, pro-plaintiff result". See Stapelton, supra note 6 at 404 - 405.

Part IV - A Stmcture for the Case Law 45

the defender were able to take advantage of the situation of impossibility. The defender

was under a duty to rernove fiom the atmosphere the silica dust fiom the negligent source

because of its potentiaily hannfUl effects. If the defender were allowed to rely on the

confusing presence in the atmosphere of dust from the non-culpable source, then no

pursuer would be able to claim against it for any injury d e r e d as a result of inhahg

dust fiom the negligent source.101

And as in Corey v. Havener, there does seem to be a basis on which responsibility for the

situation of impossibility can be pIaced on the defender. The potential objection to the

decision would have k e n if the non-culpable sources were sufficient to have caused the

injury, but this can never be known, and the reason for this is the general dust in the

atmosphere, a situation which was created by the defender. To ailow the defender to rely

on this impossibility of proving the exact proportion of dust inhaled by the pursuer would

be to allow it to take advantage of a situation it created. Aiternatively, given that the

defender had created the competing cause. and the nature of the injury being one which

was caused cumulatively fiom repeated exposure, the defender should have been able to

foresee the problems of proof the pursuer was likely to face. In combining dust fiom

innocent and non-culpable sources it must have been apparent that the pursuer would

have difficuity in distinguishing the cause.

Underlying these considerations is the fact that there was again a clear causal relation

between the act of the defender and the injury to the pursuer that was more than de

minimus. The defender couid not deny a cornplete lack of causal comection. only that

the causal effect of its negligent act was not suficient to be a legally relevant cause.

'O' See Stapelton, supra note 6 at 390.

Part IV - A Structure for the Case Law 46

Category 3 - Uncertainty as to Cause - Subsrantial Possibiiity of CmsaI Relation -

Competing Tortious Causes

The previous cases have involved the situation where it was clear that the negligent act of

the defendant contributed to some extent at least to the injury suffered by the plaintiff,

The problem in those cases was not in estabiishing the existence of a causal relation as a

matter of fact, the act of the defendant clearly being a cause of the injury, but rather

whether that cause was in itself suficient to qualiS. as the cause of the injury. We now

consider the problem of impossibility where the problem is primarily in determining

whether the defendant's negligent act had any causative effect at dl. Again we consider

this situation first where the competing causes are also tortious.

The famous example of this situation is the decision in Cook v. Lewis. 'O2 The facts of this

case are well known. Bnefly, the plaintiff and defendants were hunting in two separate

hunting parties. During the course of that expedition the defendants, while trying to

shoot a quail, both fired in the direction of the plaintiff. The result was that the plaintiff

was hit in the eye by one of the shots. The problem of evidence in the case was that

because the defendant's had fired at the same time. it was not possible to detennine

which of them had fired the shot that injured the plaintiff. One of the defendants was

clearly innocent and the other guilty.

The majority held that in the circumstances of the case, if it where impossible for the

plaintiff to prove which of the hivo defendants shot hirn, the burden of proving causation

(or rather disproving causation) would pass to the defendants. Cartwright I., with whom

Estey and Fauteux JJ. concurred, agreed with the general mle in criminal law that where

one of two individuals committed an offence. but it is uncertain which of the two

cornrnitted it, neither can be held liable "unless there are special circumstances which 37 103 render the rule inapplicable . They believed such special circumstances existed in this

102 Supra note 49. For examples of other cases within this category see Summers v. Tice (1948) 33 Cal- 2d. 80; Woodward v. Begbie CI9621 0.R 60 (H.C.); Hafr v. Lone Pulm Horel (1970) 478 P. 2d. 465; Garderter v. National Bulk Carriers (1962) 3 IO F. 2d. 2û4; Fitzgeraldv. Lune [1987] 3 W.L.R. 249 (C.A.).

Part IV - A Stmcture for the Case Law 47

case in the unfàimess of the position the defendants had placed the plaintiff. and the

potential that a deserving plaintiff would go without remedy.

Rand J., while agreeing with an approach that reversed the burden of proof. saw the

problem in temis of the impossibility that confronted the plaintiff, and responsibility for

creating that situation of hpossibility. In his view, if the plaintiff could show a tiiaher

wrong done to his remedial right of proof. then the burden of exculpation should move to

the defendant. Here he believed that the firing of the shot by the negligent actor clearly

had this effect.'04

What then the culpable actor has done by his initial negligent act is, first, to have set in motion a

dangerous force which embnces the injured person within the scope of its probable mischief; and

next, in conjunction with circumstances which he must be heId to contemplate, to have made more

difficult if not impossible the means of proving the possible darnaging results of his own act or the

similar results of the act o f another. He has violated not onIy the victim's substantive right t o

security, but he has also culpabty impaired the laner's remedial nght of establishing liabiiity. By

confbsing his act with environmental conditions, he has, in effect, destroyed the victim's power o f

proof

Cook v. Lewis is similar in many respects to Corey v. Havener. The primary concem of

the court appears to have been a desire to compensate a plaintiff who was the known

victim of a wrongfûl injury, and the absurdity of the situation whereby both potential

defendants could use the impossibility of proving causation as a complete protection

against liability. As Professor Malone has noted. in respect of a similar US. deci~ion:'~*

First, facing the court were two defendants, one or other of whom undoubtedly wounded the

victim. Can the judge afford to permit these two wongdoers to pass the bal1 of legal

responsibility back and forth between themselves while the outraged victim stands helplessly on

-

'O3 Supra note 49 at 16.

Supm note 49 at 2 - 3.

1 OS Malone, supra note 26 at 83- Professor Malone does note that this factor in itself wouid not be sufficient to support the decision. He found a fiirther policy basis in Arnerican courts' traditional strict approach to cases involving the accidental discharge o f firearms (at 84).

Part IV - A Structure for the Case Law 48

the sideline? Such a prospect is one. naturally, one from which a court will retreat whenever

possible.

In addition, the court, and in particular Rand J, appeared to rely on an element of fault on

the part of the defendants, or at least the notionally 'innocent' defendant, in creating the

situation of impossibility, The majority refer to this broadly in terms of the ''unfiair"

position the defendants have placed the plaintiff-io6 Rand J., as the above quote makes

clear, is more explicit. On his view the reason the causative effect of each defendant's

act could not be known was because of the simdtaneous discharge of the shotguns by

each of the defendants. At the very Ieast. the 'imocent' defendant helped create the

situation of impossibility. To let the two defendants take advantage of the uncertainty as

to which of them was innocent would be to allow them the advantage of an uncertainty

they themselves created. It m u t be noted. however. that Rand J. does paraphrase his

decision with the words "which he is held to contemplate", suggesting again the idea of

foreseeability.

Yet what again seems to underlie the decision is an idea of a substantid possibility of a

causal relation between the act of any one defendant and the injury to the plaintiff. Whîie

it was clear that both of the defendants did not injure the plaintiff, and that one was

innocent, if the position of either of the defendants was considered individually, there

was a substantid possibility that they injured the plaintiff. This possibility could be

expressed in percentage tenns as 50%. It was not that the causal relation was abandoued

in the case, but rather that the court recognised that it couid not be established, and still

required proof at the very least of a substantial possibility that such a causal relation

could exist.

- - - - - -- - - - - - - - - -

'O' Supra note 49 at 18 per Cartwright J..

Part IV - A Structure for the Case Law 49

Category 4 - Uncerîainîy as to Cause - Subsfunfial Possibiliiy of a Causai Relation - Compering Non-Culpable Causes

We now consider the same situation as in Cook v. Lewis, but this t h e where the

competing cause is non-culpable. Perhaps the most well known example of this situation

is the Scottish case of McGhee v. National Coaf ~oard-"' The facts of this case were the

basis of example 3 in the Introduction. The pursuer contracted dermatitis while emptying

brick kilns at the defender7s brick works. He alleged that this dermatitis \vas caused by

the defender negiigentiy exposing him to brick dust during the course of his employment

There were two specific grounds of negligence alleged. First that the defender had not

allowed the lcilns to cool sufficiently before sending the pursuer in to empty them, and

second, that the defender failed to provide shower facilities to its empioyees to allow

them the opportunity to remove the brick dust after complethg work. The first of these

grounds failed because of a lack of particularity in the pleadings and evidence, and the

pursuer accordingly could not argue that the exposure to the brick dust was itself a

negligent act. The issue therefore was whether the dermatitis was caused by the failure to

provide shower facilities.

The defender admitted that the dermatitis was caused by the exposure to brick dut , and

that it was in breach of its duty of care in failing to provide showering facilities. It

denied, however, that the pursuer had proved that the failure to provide the showering

facilities had caused his dermatitis. The basis of this deniai was that linle was known

about the cause of dennatitis, and in particular how much brick dust it was necessary to

be exposed to before the disease developed. It was therefore impossible for either party

to show whether the disease was caused by the exposure to the brick dust whiIe w o r b g

in the k i h (for which no negligence was proved) or whether it was caused by the

exposure to the brick dust between the time the pursuer finished work to the time he

'O7 Supra note 3. For other exarnples of cases in this category see Nowsco Wdl Services v. Canadian Propane and Gas & OiI (1 98 1) 122 D.L.R. 228 (Sask. CA); Letnik, supra note 5 1 ; Webster v. Chapman ( 1 997) 155 D.L.R. (4&) 82 (Man. C.A.); Bryce v. Swan Hunter Group Plc. [1988] 1 All E.R 659 (Q.B.) (although contrast the decision in that case with the decision in Winfle v. Con4us1 (Vic.) Pfy 119891 V.R 940).

Part IV - A Stntchrrc for the Case Law 50

showered at home (in which case the defender would be liable given its admitted breach

of duty in failing to provide showering facilities). In their decision, the House of Lords

held that in spite of the impossibility of proving a causal relation between the pursuer's

injury and the negligent act of the defender. the defender was tiable for the full extent of

the injuries to the pursuer.

The case clearly has sorne similarities to the decision in Bonnington Castings. To

illustrate the daerence between this case and the decision in Bonnington Castings it is

perhaps easiest to see the impossibility involved in the case as t ~ o - f o l d . ' ~ ~ The first

problem was whether the negligent act of the defendant contributed in any way to the

injury. Second was the probtem in Bonnington Castings, and whether if the defendant's

act had contributed to the injury it would have been sufficient to have caused the injury.

The majority resolved the second of these issues by adopting the more flexible standard

of proof used in Bonnington Casiings, and held that in such a case the pursuer need only

show that exposure to the brick dust before he was able to shower at home "materially

contributed" to his injury- The more difficult issue of whether the act of the defendant in

anyway contributed to the injury was resolved by what Lord Reid described as a "broad

and practical" view of causation.lw It was clear fiom the evidence that cycling home

covered in brick dust and sweat materially increased the risk of the defender developing

dennatitis. In this case, where complete knowtedge of al1 the relevant facts was not

available, the House of Lords equated a materiai increase in the nsk of the injury

occurring, with a material contribution to the occurrence of that injury, and on this basis

held that the plaintifThad proven a sufficient causal relation.

Lord Wilberforce, however, took a different approach, focused on what he viewed as the

broader policy issues involved. The question for him was whether the claim of the

pursuer must necessarily fail where it is impossible for either party to prove or disprove

causation. In his view, a consideration of the relevant factors suggested that this should

'" A similar analysis is suggested by Mustill J. in Thompson v. Smith Ship Repairers, supra note 96 at 442.

'O9 Supra note 3 at 5.

Part IV - A Structure for the Case Law 5 1

not necessarily be the case. First, he believed that it was a sound principle that where

someone breached a duty and created a risk of injury, and there was an injury within the

scope of that nsk, that that person should bear that loss unless they can show some other

cause. Second, where there is an inherent evidential difficulty, it was sound policy to

make the creator of the risk, who should have foreseen the possibility of damage, bear the

consequences of the impossibility, rather than the innocent person. In his view. these two

factors justified moving the onus of proving causation fiom the pursuer to the defender.

The decision in McGhee has provoked substantial controversy, and in particular the

judgrnent of Lord ilb ber force."^ The primary objection appears to be his open

recognition of the impossibility of proving causation, and the need to resort to an

alternative basis for determining liability in the face of this impossibility. This is then

contrasted with the approach of the majority, which is seen as simply reflecting the

'common sense' underpinning of the causation inquiryl" Yet it will be seen that even

the approach of the rnajority is one dive to the broader policy issues that can arise in

cases involving a situation of impossibility.

The majority held that. in the circumstances of the case (presumably where it was

impossible to prove causation), a matenal increase in the risk of injury coutd be equated

with a material contribution to the injury. This does not resolve the problem of causation.

As Professor Weinrib has pointed out. "[tlhere can be no contribution to the injury unless

the risk which the defendant created or increased has actually rnaterialised. and this is

precisely what the pursuer in McGhee has failed to prove."'12 What is meant by the

110 See discussion supra note 8.

"' For example, Wihher, supra note 8 .

"' Weinrib, supm note 25 at 523. Mustill J in Thompson v- Smith Ship Repairers. supra noie 96 at 442 describes this as a "fictionW- Gibbs JZ in Smith v. Moscovich (1989) 40 B.C,L.R (2d.) 49 (S.C.) at 53 stated, "Risk is not injury. There is no cause o f action for risk whether material or not. It is only when risk leads to injury that there is a claim, the claim being founded upon the negiigence implicit in creating the risk, and even then the daim can only be maintained if the causal link is proven."

Part IV - A Structure for the Case Law 52

circumstances of the case simply becornes a mask for liability based on other

unarticulated policy considerations

Indeed in the majority judgments, other than that of Lord Reid, there is explicit reference

to considerations other than the simple application of a 'broad' approach to causation,

Lords Simon and Salmond refer to the potential for an unenforceable duty if the plaintiff

were unable to recover in this case."3 If the defender were not liable, it would mean that

they "were under a legal duty which they could, in the present state of medical 0-1 14 knowledge, with knpunity ignore-' Lords Simon and Kilbrandon also refer to a basis

of fault on the part of the defender in respect of the situation of impossibiIity. Lord

Simon notes that the fmding that the provision of showering facilities was a reasonable

precaution means that the defender must have foreseen that if such facilities were not

supplied, there was a greater nsk of its employees contracting dermatitis. Lord

Kilbrandon adopts an almost estoppel like analysis in the following cpotation.' I 5

When you fmd it proved (a) that the defenders knew that to take the precaution reduces the risk,

chance, possibility or probability of the contracting of a disease, (b) that the precaution has not

been taken, and (c) that the disease has supervened, it is difficult to see how these defenders can

demand more by way of proof of the probability that the failure caused or conmbuted to the

physical breakdown.

So McGhee raises the same concems as those in the previous cases we have considered.

The first was the prospect of an unenforceable duty. The defender was under a duty to

provide s h o w e ~ g facilities, the very purpose of which was to ailow its employers to

remove the brick d u t ffom their skins and avoid contracting dennatitis. However, if it

I l 3 Lord Salmon takes a slightly different approach in this regard, although in substance it is the same. On his argument, if a materiat increase in the risk could not be sufficient for causation, then there would be the nonsensical situation where if an employee with a 52% possibility of contracting dermatitis had that possibility increased to 90% by the act of a negligent employer, that employer could never be Iiable because it could always be said that even without the precaution it was more probable than not that the ernployee would have contracted dermatitis.

Part IV - A Structure for the Case Law 53

was not possible for anyone to distinguish the causative effect of working in the factory

fÎom the opportunity to remove the brick dust by showering, then no empioyee would be

able to claim against the defender for failing to provide the showers. The defender would

always be able to say that the dermatitis may have been caused by work in the factory,

and the pursuer would be unable to prove otherwise.

The second concem was the element of fault or responsibility on the part of the defender

for the situation of impossibility. This could be categorised in two ways. First, the

reason the causative effect of the defender's negligent act couId not be known was

because of the competing cause, narnely the exposure to brick dust during the course of

work. While this exposure was not in itself negligent, it ciearly had the effect of

rendering it impossible to distinguish the effect of the negligent cause tiom the non-

culpable cause. Yet the court also referred to a broader basis of fault on the part of the

defender in its foresight of the evidential dificulties that would arise. The very purpose

for which the showers were to be provided was to prevent the risk of dermatitis, and in

such circumstances, it was not difficult to say that the defender should have foreseen the

problems that could arise in proving the cause of any dermatitis if it failed to provide

those showers.

Yet underlying these two considerations must again be a recognition of the substantial

possibility that the defender's negligent act was a cause of the injury There was oniy

one possible cause of the dermatitis in a broad sense, narnely the exposure to the brick

dus . The reason the defender was under a duty to provide showers was because it was

known that dermatitis could result fiom exposure to brick dust, and thorough washing

was the only known precaution that could be taken against the onset of such a condition.

In circurnstances where the defender ultimately did develop dermatitis, and neither the

culpable nor non-culpable causes could be eliminated, it remained on those facts a

substantial possibility that the failure to provide showers at the very least contributed to

the injury.

Part IV - A Structure for the Case Law

Category 5 - SpecuIafive Causal Relation - Competing Tortious Causes

As was discussed earlier, where a plaintiff is able to show that al1 causes are tortious, the

Court will be confkonted with a choice benireen a nurnber of tortious actors. each of

whom may possibly have caused the injury. In cases such as Cook v. Lewis. where there

was o d y a limited number of defendants from which to choose, in imposing liability on

either defendant, regardless of any evaluative considerations, the statistics themselves

suggested a substaatial possibility in respect of each defendant that they were the cause of

the injury. Yet this justification bezornes more difticult when the number of possible

defendants is increased to a Iarge number. so that the statistical basis for assuming the

possibility of a causal relation in respect of any one defendant is removed, and indeed

suggest that it is very unlikely that any one of the defendants caused the injury. To

consider this problem we can use the case oiSindeII v. Abbott Laborotories. ' '"

DES was a dmg marketed by the defendants as reducing the chances of rniscarriage in

pregnant mothers. In fact, it had little effect in reducing miscarriages, and could also

cause a v i d e n t fonn of cervical cancer in the daughters of mothers who took the dmg.

Eventually the defendants were required to remove the dmg fiom the market. The

plaintiffs mother had taken the dmg during pregnancy, and the plaintiff was later

diagnosed with a nialignant tumour on her bIadder which had to be removed. She was

now constantly monitored for any return of the cancer. She alleged that her cancerous

condition was caused by her mother taking DES during her pregnancy, and that the

defendants were negligent in manufacturing and marketing the dmg. The difficulty she

faced in proving her c l a h was that the cancer had a substantial latency period. and that

because of the time that had elapsed since her mother took the drug, it was impossible

now to identw the manufacturer that had produced the dmg conswned by her mother.

Enstead she joined 5 of the approximateiy 200 manufacturers of the dmg (who accounted

-

116 (1 980) 607 P9d 924. For other examples o f this category see Binder Minepex v. Barnes (29 July 1997 NS W Lexis 946) (C.A.); ICI Ausrraiia Operations Pry Ltd v- Walsh and ors (3 October 1997 NS W Lexis 1164 (C.A.)).

Part IV - A Structure for the Case Law 55

for 90% of the market), and argued that the burden lay on the defendants to show that

they were not the manufacturer of the dnig which her mother had consumed.

The court upheld the plaintiffs argument. The reasoning of the court is perhaps best

surnmed up in the following quotation. 117

The most persuasive reason for finding plaintiff states a cause of action is that advanced in

Summers: as between an innocent plaintiff and negligenr defendants, the later shoutd bear the cost

of the injury- Here, as in Summers, ptaintiff is not at fault in failing to provide evidence of

causation, and akhough such evidence is not amibutabte to the defendants either. their conduct in

marketing a drug the effects of which are delayed for many years pIayed a significant role in

creating the unavailability of proof.

The court held each defendant liable according to their market share. This was intended

to reflect the likelihood that any defendant supplied the drug that the plaintiff s mother

took. The court also noted that for such a doctrine to apply the plaintiff must have joined

a "substantial share" of the manufacturers to the action. Each manufacturer was entitled

to prove that they did not supply the dnig to the plaîntiffs mother and therefore avoid

liability.' l 8

What is immediately striking about the decision is that liability appears to be based on

principles similar to those in Corey v. Huvener and Cook v. Lewis. The principle concem

of the court, as noted in the above quote. is that the plaintiff who is able to show that she

has suffered a wrongfùl injury will be Ieft remediless in the face of a group of defendants,

one of whom in al1 probability (90%) caused that injury. In addition it was clear that

each defendant caused a wrongful injury to some plaintiff. although the exact identity of

that plaintiff was unknown. We also see in the case a concem that the defendants

contributed to the impossibility of proving the precise causal relation. They

"' Ibid. at 936 - 937 per Mosk, J..

118 In a similar case, however, the Court of Appeals of New York refiised even to allow the defendants this possibility. This was said to follow fiom liability being based not on causation in a single case. but rather on a market basis. See Hymowitz v. EZÏ Li& & Co. ( 1 989) 539 N E 2d. 1069 at 1078 per Wachtler CJ.

Part IV - A Structure for the Case Law 56

manufactured a generic drug which caused a cancer with a long latency period, It was

this delay that the court appeared to treat as the cause of the impossibility of proving

which supplier produced the drug that the plaintiff s mother consumed.

However, the major difference between this case and cases Iike Corey v. Hmener and

Cook v. Lewis is that the nature of any causai relationship between the act of any one

defendant and the injury to the plaintiff was at best speculative. First, this was not a case

where the defendant would have been liable on proof of some lesser causal relation such

as a substantial contribution to the injury- The plaintiff either suppIied the dnig which the

plaintiff s mother consumed (and therefore caused the injury) or it did note When the

position of each defendant is considered it seems ctear that to assert that any one of them

supplied the dmg that was consumed by the plaintiff s mother was pure speculation. It

could have been any one of 200 manufacturers. And this speculative causal relation

seems reflected in the court opting for an imposition of liability based on market share,

rather than the more usual joint and several liability among tortfeasors.

lndeed the view of many commentators, and many commonwealth jurisdictions, is that

the decision can only be justified if exposure to the risk of developing cancer is seen as

the relevant i n j ~ r ~ . ' ' ~ While the relevant injury is the development of cancer in the

plaintiff, it seems clear that the decision c a ~ o t be justified according to established

principles of tort law, precisely because of the declining probability that any one

defendant was the cause of the injury. Professor Wright comments on this aspect as

follows. I2O

I l 9 For example, Celli, supra note 7 at 638.

120 Wnghf supra note 26 at 18 17 - 18 18. Professor Fleming similarly believes the decision cannot be justified according to established principles of liability in tort law: "A number of objections have been raised against this sotution ... By far the rnost formidable is that it departs from the prior art not merely by lacking ail precedent but by being incompatible wîth the traditional notion of tort law as a system of individual responsibility, This was not corrective but distributive justice. Despite the court's disavowat, it was indeed an industry-wide liability, which did not conform to basic notions about individual justice. Such a break h m the whole tradition of out- culture should be at best a program for legislation, not judicial reform." FIemïng, supra note 6 at 668. Ripstein &k Zipursky, supra note 13, however, have argued that because it was known that the plaintiff had suffered a wrongful injury, and the defendant had inflicted a wrongîül injury, the causation requirement was in substance satisfied.

Part IV - A Structure for the Case Law

As the nurnber of defendants increases. the departure from the usual principles of tort law becomes

even more apparent and diffkult to justiQ. Thus, if there are N defendants, we know that N - 1 of

them are being held liable even though they did not conmbute to the injury. As N increases, the

probability that any particular defendant is the one who caused the injury becornes increasingly

smal1. The argument that the negligent defendants. rather than the innocent plaintifTm should pay

for the mjury becomes more a penal argument han a tort argument. ,.. In effect the argument

asserts that it is better that IV - 1 defendants who did not contribute to the injury should pay for it

than that the one who did cause it should go fiee, Moreover, the one that did cause it rnay pay for

little or none of the damages, due to contribution or insoIvency.

So it is suggested that while the decision in Sinde22 may be justifiable on wider grounds

of policy, and in particular as a response to the unique and widespreûd problems

presented by the DES litigation, it cannot be justified on ordinary tort principles that treat

the physical injury to the plaintiff as the relevant injury for the purposes o f imposing

liability. The reason for this is simply that the causal relation between the plaintiff and

any one defendant was too speculative.

Category 6 - Speculafive Causal Relation - Cornpethg Non-Cdpable Causes

We now consider the situation where the potential causai relation is, as in Sindell, of a

more speculative nature- but the competing causes are non-culpable. A good illustration

of this situation is the decision in Wilsher v. Essex A.H.A..'" In that case the plaintiff

was boni 3 months premature, and as is common in such children, encountered a number

of medical problems. D u ~ g his treatment the doctors wrongfully inserted a catheter into

a vein rather than an artery, which had the result of increasing the oxygen flow to his

brain. Increased oxygen flows can cause blindness, and indeed it was subsequently

discovered that the plaintiff was blind in one eye. and had severely impaired vision in the

other. However, this condition (RLF) can also be caused by a number of other n a d

causes al1 of which the plaintiff suffered fiom. In the cucurnstances of the case it

'" Supm note 8. F G ~ other examples of this category see Blackstock v. Fosrer [ 19581 S.R. (N.S. W.) 34 1 ; Kay v. Ayrshire, supra note 17; Smith v. Moscovich. supra note 1 12; Pedro Juan CabilIo v- CommomveaIth of Ausrrufia (14 Decernber 1995 NSW Lexis) (Fed. Ct. N.S.W.); Wintle W. Conousr (Vit.,), sicpru note 107.

Part IV - A Stmcnire for the Case Law 58

appeared to be impossible for the plaintiff to show that the exposure to increased oxygen

levels caused or materially contributed to his blindness.

It was accepted before the House of Lords that the defendant had been negligent in

inserting a catheter into a vein rather than an artery, and that this led to increased oxygen

flows to the brain. However, the court held that in spite of this impossibility, the

plaintiff s claim would fail if he could not prove a precise causal relation betweçn the

increased oxygen flows and his subsequent blindness. Because the trial judge had

determined the case on the basis of an incorrect principle, certain important findings of

fact in relation to the issue of causation had not been made, and the case was sent for

rehearing on this issue. Yet it seems clear from the decision that if the trial judge

detennined that it was impossible to establish the exact cause of the plaintiff s injury,

then his claim wouid fail.

The case has strong sinùlarities to the decision in McGhee, and indeed the case was

argued on the basis of that decision. Some of the factors we identified in McGhee as

explaining the court's decision are also present in WiIsher. It seems clear that the

defendant did not, as was suggested by Rand J. in Cook v. Lewis, appear to have created

the situation of impossibility. Nor was it responsible for the existence of the other causes

which, combined with the negligent act of the defendant, made it impossible to discern

the precise cause, as was the case in hfcGhee. Yet it does not seem unreasonable to say

that the defendant should have at least foreseen the difficulties the plaintiff might face in

proving the effect of its negligent act. While it would clearly need to be the subject of

further evidence, where the defendant exposed the plaintiff to a new negligent cause, that

created the risk of him contracting RLF. the defendant should have foreseen the

difficulties the plaintiff would face in identiwing the exact cause.

It is more difficult to assess the potential for an unenforceable duty, given that this was

not addressed by the court. There seems to be such potential in the fact similar problems

of proof may arise in the fùture when treating premature children. What is unclear is

whether the nature of the evidential impossibility would also arke on such an occasion.

Part IV - A Structure for the Case Law 59

In any future case it may be that the plaintiff did not s a e r h m the other conditions that

could have caused the injury so that the causal relevance of the defendant's act would be

easier to discem. The failure of the plaintiffs c l a h in the case did seern unique to the

individd case, a specific failure in the evidence, rather than creating a situation whereby

the defendant would effectively be shielded fiom al1 future liability. In this respect the

potential for an unenforceable duty does not seem as strong as that in McGhee.

Yet perhaps the most important consideration in the case, and the most important

ciifference fiom McGhee, is the lack of any substantial possibility that the defendant's act

was a cause of the plaintiff s injury. There were a number of causes, each of which the

plaintiff suffered Erom, and al1 of which seemed equally likely to have caused the injury.

The defendant's act sirnply added another possible cause to a number of pre-existing

causes. This is usuaüy regarded as the point of distinction between McGhee and WiIsher.

As Mustill L.J. noted in the Court of Appeal decision, in WiIsher the "uncertainty is 7 ,122 greater. Marc Stauch, in an article reviewing the decision, suggests that the court was

making the point that '2he greater the number of other candidate conditions that could

have completed causal sets (five in Wilsher as opposed to two in McGhee). and the more

limited the defendant's control over them. the less willing the court will be to infer that

the condition contributed by the defendant's breach was causative of injury.""'

IY)[l 9871 1 Q.B. 730 at 771.

Stauch, supra note 6 at 215. See also A. Boon. "Causation and the Increase of Risk" (1988) 5 L M.L.R. 508.

Part V - A Rationale for Cases Involving a Situation of Irnpossibility 60

PART V - A RATIONALE FOR CASES INVOLVING A SITUATION

OF IMPOSSIBILITY

In the previous Part, we considered examples of the various types of cases that may arise

involving a situation of impossibility, within a structure that reflected what it is that we

could know about the causes of the plaintiff s injury. What that structure did not tell us,

being merely descriptive of the cases? is why we wodd treat cases involving a situation

of impossibility differently from the ordinary case where a plaintiff fails to prove

causation, and when would we do so. We now try and answer these questions using that

analysis of the cases in Part IV.

Our consideration of the case law raised four possible answers to the questions just

posed. These were a concern that if the plaintiff s claim failed then the defendant could

never be held liable for injuries she uiflicted (the idea of an unenforceable duty), a

concem that comparatively the defendant kvas more to blarne than the plaintiff for the

situation of impossibility, the certainty that the plaintiff has suffered a tortious injury and

would not be cornpensated (or occasionally that the defendant has caused a wrongful

injury and will not be required to compensate), and the degree of uncertainty of a causal

relation. It will be suggested that consideration of the first three of these factors (as

properly understood) explains why cases involving a situation of impossibility are treated

differently fiom other cases. While not necessarily present in any one case. mmy cases

involving a situation of impossibility raise the prospect of any one of these three concems

arising if the plaintiffs claim is necessarily to fail. These factors has prompted courts to

relieve the plaintiff of the burden of proving causation when it is impossible to do so.

However these factors alone are not sufficient to explain when a court will relax the strict

requirements for proof of a causal relation. What is apparent from our review of the

cases is that the courts still require vindication of the causal requirernent to the extent that

it is possible. This is ïeflected in the fact that a plaintiff will only succeed where she is

able to show either that the defendant's tortious act contributed to her injury, or that there

is a substantial possibility that it contributed to or caused her injury. If she is unable to

Part V - A Rationale for Cases involving a Situation of Impossibility 61

establish either of these possibilities then her claim will fail in spite of the strength or

otherwise of these broader policy consideratiom.

The Unenforeabble Duty

Many of the cases considered in Part IV suggested that the problem in cases involving a

situation of impossibility is that the existence of the impossibility of proving a causal

relation means that the defendant is effectively under a duty she is f?ee to ignore. This

concem was expressed in two ways. First. it was part of a broader concem that where it

was certain that the plaintiff had suffered a wrongfui injury, then the situation of

impossibility meant that she would fa11 between the "stools" of the various defendants,

who between them had clearly caused her injury. This was particularly evident when al1

possible defendant's were before the court, as was the case in both Corey v. Kavener and

Cook v. Lewis. Second, this concem was made explicit in cases where it was uncertain

whether the defendant had suffered a wrongfUi injury. McGhee, and in particular the

judgments of Lords Salmond and Simon. were a good illustration of this.

Before considering what is meant by the phrase 'an unenforceable duty'. we need first to

explain how it arises in cases like Corey v- Hmenet and Cook v. Lewis. The argument

that is made in those cases of the plaintiff falling between the 'stools' of liability includes

two elements; certainty of wrongful injury (and therefore that a deserving plaintiff will

not be cornpensated), and the escape of a -guilty' defendant (that is, the idea that the duty

the defendant is under wiIl be effectively unenforceable). The importance of proof that a

plaintiff has suffered a wronghil injury wIll be considered later. Here, in considering the

potential for an unenforceable duty, we are focused on the nature of the breach ofduty by

the defendant, and the relevance of the evidential dificulty in the case to that breach of

duty. That issue, as the decision in Sindell illustrates, arises regardless of whether there is

proof of a wrongfiil injury.

Part V - A Rationale for Cases Involving a Situation of Impossibility

The Nature of an Unenforceable Duty

First we need to consider what we rnean when we describe a duty as king

'unenforceable'. Tort law, and in particular the law of negligence, does not enforce d l

breaches of duty. 1 can drive my rattling old jalopy as quickly as 1 like down a crowded

Street, pouring toxic substances out of my tailpipe, hurliag threats at whomever I please,

as 1 tow my overloaded and unsecwed trailer to the tip. Tort law does not 'enforce' any

of the manifest breaches of duty 1 have cornmitted to other drivers on the road, nor

pedestrians on the sidewalk. It only enforces those duties if they cause injury to another.

So it is not the fact that a negligent act will not be 'punished' that is the concern of the

unenforceable duty. Rather it is. in its most basic fonn, that the duty will be

unenforceable against a defendant who has caused a tortious injury.

Yet our understanding of what would constitute an unenforceable duty, to have meaning

in the context of a case involving a situation of impossibility, needs to be refined M e r .

In such a case, we do not know whether the defendant caused the injury to the plaintiff,

so we cannot Say that there is an unenforceable duty simply as between the plaintiff and

defendant in the particular case. In such a case. there would be no certainty, in any sense,

that this defendant has caused an injury. Al1 the idea of an unenforceable duty would do

is express the possibility that the defendant caused the injury, the relevance of which is

met by the equal possibility that the defendant did not cause the injury. Rather. because

we are concemed with a defendant who has in some sense 'injured' someone to escape

liability, we must focus on the potential for any breach of duty by the defendant (or any

other defendant) to apply to other plaintifEs. Understood in this way, the unenforceable

duty requires, at the very least, an abstract certainty that a defendant will escape liability

for hann she has caused.

When the idea of an unenforceable duty is understood in this way, it provides some

valuable insights into the cases considered in Part IV. Cases where the potential perçons

embraced within the breach of duty by the defendant were limited, or where the nature of

the duty and breach is one that is not likely to arise in other circumstances, do not seem to

Part V - A Rationale for Cases Involving a Situation of Impossibility 63

raise the prospect of an unenforceable duty. Corey v. Havener and Cook v. Lewis are

good examples of this situation. The negligent act by the defendant did not create the

potential of injury to other plaintiffs, nor was it a situation that was Iikely to arise again in

the friture. It lacked any potential for application in other cases. If the duty was

unenforceable, it was only unenforceable by that plaintiffagainst those two deFendants.

Yet the situation in a case such as Wilsher seems different, While the negligent act of the

defendant included only the plaintiff in the potentid scope of its nsk, the negligent act

itself was one that seemed likely to arise again. To an extent, this staternent codd be

made in respect of ail cases involving a situation of impossibility. üiciuding Corey v.

Havener and Cook v. Lewis. But in Wilsher, and indeed in many cases of medical

misadventure, there is clearly a concern with the potential application of the principle in

one case to another. In particular. the concem is that if it is impossible for a plaintiff to

prove a causal relation in such cases. doctors will effectively be fiee to practise as

negligently as they like, as long as the prospects of the plaintiff recovering or developing

fürther injury are less than 50%. This concem cm be expressed as one focused on the

potential for an unenforceable duty, albeit one in its most broad fom. In such a case,

there is abstract certainty that a defendant would cause injury to a plahtiff when similar

cases arise.

However, the nature of the duty and breach in Bonningron Castings and McGhee seem to

be different again. In Wilsher the possibility of a defendant cornminhg this wrong to

other plaintifEs was still only abstract. In these cases. however, the negligent act of the

defendant has itself created this possibility. The negligent act embraced a nurnber of

potential plaintiffs. It was a breach of duty not only to the plaintiff in the action, but also

to al1 their employees. If the breach of duty by the defendant was unenforceable in the

particular case before the court, then (depending on the nature of the evidential

deficiency), it would be unenforceable by any future plaintiff some of whom the

defendant by his negligent act injured. There was accordingly a certaine that the

defendant had injured a plaintiff in a different sense. While the defendant may not have

injured the particular plaintiff, the nature of its act was such that it would probably have

Part V - A Rationale for Cases Involving a Situation of Impossibility 64

injured some other plaintiff, and in those cases because of the situation of impossibility it

would not be liable for injuries it clearly inflicted.

Yet the idea of an unenforceable duty is most clearly demonstrated by a case such as

Sindell. In Bonningion Castings and McGhee it was only certain in an abstract sense that

the defendant caused injury to some plahtiffs. However in Sindell, this possibility was a

factual certainty. The possible plaintiffs aEected by the defendant's negligent act were

before the court in the form of a class action. It was therefore known that the defendant

had injured some plaintas, the difficulty was only in proving a causai relation between

any particular plaintiffmd the defendant. The situation of impossibility would mean that

a defendant who definitely injured some phintiffs would never be held liable- The duty

the defendant was under was effectively rendered unedorceable by the situation of

impossibility.

The lVature of the Evidenfial Gap

A further point rnust be noted about this idea of an unenforceable duty. Not only must

the nature of the duty be such that it has potential application to a broad number of

plaintiffs, but the nature of the evidential gap mut also be one which is likely to arise in

such cases. We see this again in Bonningtort Castings. MkGhee, and SindeZl. In al1 these

cases, the problem the plaintiffencountered in proving her case was one that was likely to

occur (or in the case of SindeZZ actually did occur) in any fiiture case. This is not

necessarily the case. For example if the problem in McGhee was not a general inability

to understand how dermatitis \vas caused, but rather that the plaintiff had covered himself

in a cream that as a side effect made it difficult to determine the cause of the dermatitis,

there is no reason to think that such an evidential difficulty would mise in any fbture

case. In such a case, while the breach of duty itself rnay have potential application to

other cases, the evidentiai difficulty would not. This rnay in tum explain the reason this

issue did not arise in Wifsher.

Part V - A Rationaie for Cases lnvolving a Situation o f Impossibility

The Signzjicance of the Unenforceable Dzriy

So we see fiom the above discussion that many cases involving situations of

irnpossibility may, to varying degrees, mise the potential for an unenforceable duty. The

importance of this feature wiU depend on the nature of the duty the defendant was under

and the nature of the evidential gap. But in a case like Sindeil, and to a lesser extent

cases like Bonningîon Custings and McGhee. where it is clear that a defendant who in al1

probability caused injury to some plaintiff will escape liability because of the situation of

impossibility, it presents itseif as a reason for treating these cases differentiy f?om the

ordinary case where a plaintiff fails to prove causation. It must be noted. however, that

the presence of an unenforceable duty does not explain when such an allowance will be

made. The factor was not present in cases such as Corey v. Havener and Cook v. Lewis

but was present (in its strongest fom) in Sindell. it is a factor that helps explain why we

Wght treat cases involving a situation of impossibility differently, but does not explain

when we will do so.

The Requirement of Fault

A second feature that was suggested in our review of the case law as a consideration of

importance in cases involving a situation OF impossibility, was fault on the part of the

defendant in actively creating the situation of impossibility (in the sense of destroying the

plaintiff s power of proof), or at least foreseeing the possibility that such a situation could

arise. This 'fault' was contrasted with the apparent 'innocence' of the plaintiff and used

to argue that the defendant should bear the consequences of the plaintiffs inability to

prove causation.'" It is an argument that, if correct, has some significance. If the

situation of irnpossibility is the responsibility of the defendant, why should the plaintiff

have to suffer the consequences? It is not the plaintiff s fault that the situation arose, yet

it effectively bars her claim against a defendant who rnay have caused her injury. There

Iz4 In addition to the cases considered in Part W. see also Nowsco Weff Services v. Canadian Propme and Gas & Oil, supra note 107 at 246 per Bayda J.A.: Haag v. Marshall (1989) 39 6.C.L.R 205 (C.A.) at SI3 per Lambert J.A.

Part V - A Rationde for Cases Involving a Situation of ImpossibiIicy 66

seems to be something inherently &air in allowing the defendant the advantage of an

uncertainty of causation for which she is responsible, and which is hiding the true effect

of her negligent action.

It will be suggested that the idea of a defendant 'creating' a situation of impossibility by

'destroying' a plaintiffs power of proof has some difficulties, as it generally equates

proof of a negligent act with fault on the part of the defendant. However. a particular

understanding of the idea of foresight of the possible evidential dificulties the plaintiff

would face, based on the circwnstances of the individual case, does offer a basis for

attnbuting responsibility to the defendant for the situation of impossibility in these cases.

It provides the basis of the normative argument that because the defendant is responsible

for the situation of impossibility, she should suffer the consequences of her actions-

The 'Innocent ' Plaintlr

In al1 of the cases inwlving a situation of impossibility that were considered in Part IV, it

was clear that the plaintiff was not responsible for creating the situation of impossibility.

The plaintiff had suffered an injury. which may or may not have been the result of a

negligent act by the defendant. but it was impossible for her to show who caused that

injury. If this situation arose through no fault on her part, the question was whether she

should necessarily suffer the consequences of the impossibility, particularly if the

situation was the responsibility of another person. On the other hand, if she did create the

situation, the problem was one of her own making. and it does not seern unreasonable to

make her s a e r the consequences of her own actions. The cases suggest that a plaintiff

must be able to show that she is not responsible for the situation of impossibility.

nie necessity of this aspect, while clear from the cases considered early, can be nicely

demonstrated by the decision in Lange v. Bennett. "' The facts of the case were simïlar to

those in Cook v. Lewis. The plaintiff and a group of three other young boys (including

125 Cl9641 0.R 233 (Ont- HE.). See also Food Gianr Markets v. W a ~ o n Leareholds (1987) 43 C.C.L.T. 152 (Alta, Q.B.); Birkholz v. Gilbertson Pfy. Ltd ( 1 985) 3 8 S.A.S.R 12 1 (S.C.) at 146 - 147 per Bollen J..

Part V - A Rationale for Cases Invotving a Situation o f IrnpossibiIity 67

the two defendants) were out hunting. They sighted a bird and al1 four opened fire. The

plaintiff was standing in fiont of the two defendants. and while they were firing he stood

up and was stmck in the head by a shot fiom one of them. Again, as in Cook v. Lewis, it

was in the circumstances impossible to Say which of the two î3ed the shot that injured the

plaintiff. However, the court refbsed to apply the decision in Cook v. Lewis because the

plaintiff had himself k e n negligent in standing up white the defendants were firing

behind him and had therefore, in the view of the cou& participated in the destruction of

his own meam of proof. '*'

The plaintiffat the tirne of the accident was two years order than the defendant. He kneeled down

to shoot and knew that he was in approximate line of fire of two younger boys. shooting h m

behind him. He was unquestionabiy negligent in standing up without warning and putting himself

into the line of fire. He mua be taken to have known that it would be difficult to Say in such

circumstances which boy fired the shot that stmck him. He had himself participated as a

"negligent actor" in the "proof destroying fact*". To hold on these facts that one who may have

done him no ham should pay damages because he could not clear himself h m blame would be

grossly unjust. ... 1 have found no case where a plaintiff who was himself negiigent has been able

to avail himself of the doctrine of Sumrners v. Tice and 1 do not think that Cook v. Lewis should be

extended to such a case.

The 'innocence' of the plaintiff appears here as a b a i s of exclusion. I f the plaintiff

created the situation of impossibility. then she shouId usuaily s a e r the consequences of

her action. Yet it is also important as part of a broader argument that the strict d e s for

proof of causation should be relaxed in cases involving a situation of impossibility when

it is cornpared to fault zz the part of the defendant in respect of the situation of

impossibility .

Fault on the Part of the Defendant

The element of fault on the part of the defendant was one of some importance in many of

the cases considered in Part IV. Yet it is not entirely clear what was meant by the courts

- - -

''' Ibid. at 237 - 239 per McRuer, CJ..

Part V - A Rationale for Cases Involvinp a Situation of impossibility 68

when they talked of fault. There appeared to be two separate senses in which this idea

was used. First was in terms of the defendant actively creating the situation of

impossibility, or in other words destroying the plaintiff s power of proof, Second, was in

terms of the extent to which the situation of impossibility was foreseeable by the

defendant.

a) Creating the Situation of lmpossibiliîy - Destrucrion of the Plaintiffs Po wcr of Proof

In many cases involving a situation of impossibility, there is discussion of a defendant

'creating' the situation of impossibility by 'destroying' the plaintiffs power of proof.

The clearest example of this is the judgment of Rand J. in Cook v. Lewis. Yet we need

to ask how it is that a defendant could 'destroy' a plaintiffs power of proof. and in this

regard there seems to be two possibilities Either. in addition to her negligent act, the

defendant has committed a M e r wrong to the plaintiffs power of proof, or a

consequence of her negligent act has been to destroy the plaintiff s power of proof.

1 have not found an example of this Fust possibility, so a hypothetical example will have

to do, based on the decision in Cook v. Lewis. If we imagine that there was in that case

also evidence that ordinary ballistics test would have identified who fired the shot that hit

the plaintiff, but that both defendants had filed down their gun barrels prior to the hunting

expedition so that individual characteristics that may identiQ their guns were removed.

In such circumstances, it does not seem difficult to understand the conception of fadt that

would be involved. The defendants deliberately removed the means of identifLing their

bullets, and the plaintiff is consequently unable to show who fued the bullet that injured

him. The defendant in this sense could be said to have actively created the situation of

impossibility.

Yet such a situation is likely to be a rare occurrence. The more common situation, and

the argument that could potentially be made in respect of al1 the cases we have

considered so far, is where the very act of negligence (which is the basis of the plaintiffs

claim against the defendant) is also used as the basis for arguing that the defendant has

Part V - A Rationale for Cases Involving a Situation of Irnpossibility 69

created the situation of impossibility. That is, the negligent act caused an additional

wrong to the plaintiff in destroying her ability to prove causation. An example of this is

the judgment of Rand J in Cook v. Lewis. On his approach, the act of firing by the

notionaily 'innocent' defendant confùsed "his act with environmental conditions" and in

effect "destroyed his victim's power of proof'.'27 %y creating another possible cause, the

defendant created a situation of confusion in which the plaintiff could not identw the

actual cause of his injury.

Where it is aileged that a negiigent act of the defendant caused the plaintiff s injury, this

conception of fault, it is suggested. does Iittle to advance our inquiry. It simply equates

fault on the part of the defendant in creating the situation o f impossibility with the fault

inherent in her commission of the negligent act. In any case where it is impossible for

causation to be proved, the defendant has cornmitted a negfigent act, and that negligent

act urill have added another potential cause to the list of possible causes of the plaintiffs

injury. For example, in Blackstock v. Fosrer. the negligent act of the defendant simply

added another cause to the possible causes of the malignancy. It can always be said in

these cases that if the defendant had not cornmitted the negligent act, the plaintiff wodd

not face the difficulty in distinguishing between causes. If this were to be accepted as a

reason for treating cases involving a situation of impossibility differently, it would mean

that in every case where it is impossible Cor a plaintiff to prove causation. that situation

could be described as being the fault of the defendant. The fault element would simply

be equated with proof of negligence.

b) Foresight of the Situation of hpossibiIiîy

A second conception of fault on the part of the defendant that arose out of our review of

the cases was that of foresight by the defendant of the possibility of the situation of

impossibility. The fault here was not in the defendant actively creating the situation of

impossibility, but rather that in addition to foreseeing the possibility of injury, the

defendant should aiso have foreseen the difficulty that may mise of proving the cause of

127 Supra note 49 at 4.

Part V - A Rationale for Cases Involving a Situation of ImpossibiIity 70

that injury. On this understanding of the fault of the defendant, not only has the

defendant created a risk of injury, but she has also created a risk that if the injury did

occur, it would be impossible to determine its cause.

Foresight of a situation of impossibility c m easily becorne, as with the idea of destroying

a plaint8Fs power of proof, simply a way to equate fauit on the part of the defendant with

the commission of the negligent act. For exarnple, to use BIuckstock v. Fosrer again as

an exarnple, if the defendant should have foreseen the likelihood of the impact on the

plaintiffs chest aggravating an e,uisting condition, then it does not take much of an

extension in the degree of his foresight to Say that he should have foreseen that it may be

dificuit for the plaintiff to distinguish the effect of the negligent act fiom the effect of

any pre-existing condition. Foresight in these tenns is of limited assistance. As with the

idea of a defendant 'creating' the situation of impossibility by 'destroying' the plaintiff s

power of proof, it simply equates liability with proof of negligence.

But if we consider the particular way in which foresight was approached in many of the

cases considered in Part IV, and in particular cases in categories 1 to 4, we see a reliance

on particular features of the case which suggest foresight on the part of the defendant,

features which appear as unusual when compared to the ordinary case. We see this, for

exarnple, in Cook v. Lewis. There. the 'innocentT defendant was aware of the existence

of the other hunter, the location of the plainti ff. and that the other hunter was 1 ikely to fire

at the same time as him. It was not simply that the two defendants happened to

independently fire in the direction of the plaintiff. but rather that they did so in full

knowledge of the presence of the other defendant, and his likely action. In those

circurnstances, it is not difficuit to suggest that the defendant should have foreseen the

possibility that it may not be possible for the plaintiff to distinguish the source of the shot

if she were hit. The same would appear to be true oFCorey v. Havener.

McGhee shows a sirnilar characteristic. There, the specific reason the defendant had a

duty to provide the showering facilities was because it was known that dermatitis can

develop fiom exposure to brick dust. The duty existed for the specific purpose of

Part V - A Rationaie for Cases Involving a Situation o f Impossibility 7 1

removing the possibility of injury that the defender's own act had created. Again it is not

difficuit in such circumstances to Say that the defender should have foreseen that if the

pwsuer developed dermatitis when he had failed to provide such showers. it wouid be

difficult for the pursuer to show the cause of his injury. Bonnington Castings is similar in

this regard. There the defender, in mixing dust fiom a negligent source with dust he was

already exposïng the pursuer to. it must have been foreseeable that if the pursuer were to

develop pneurnoconiosis it may be impossible to determine the extent to which the

negligent source of the dust contributed to that injury.

And this does seem to be a point of distinction between these cases and sorne of the other

cases considered in Part IV. For exarnple in Blackrrock v. Foster, a case which it was

suggested should be considered in category 6 , the defendant neither knew of the existence

of the other cause, nor had any reason to believe that it may be difficult to identw the

effect of his negligent action. in contrast to the other cases. he had no knowledge of, or

control over the other sources of the injury. In those circumstances its seems difficult to

Say that he could have foreseen the difficulties the plaintiff faced.

Underlying ttïis conception of fault seems to be an assumption that the consequences of a

defendant's action should be identifiable. Such an assumption is reflected in the concept

of a burden of proof, and in particular cases like Reed v. Ellis, which hold a plaintiff

responsible for failing to produce sufficient evidence to establish the liability of a

defendant. Yet cases involving situations of impossibility, where this element of

foresight is present, are cases where this expectation is clearly not justified on the

particular facts of the case. From what the defendant should have known. it should have

been apparent to her that the consequences of her action were, in fact, zrnlikely to be

identified. In these cases it does not appear that the defendant is entitled to Say that the

consequences of her actions could be identified.

Fault in these tems provides another reason for treating cases involving a situation of

impossibility differently, but again it does not explain when a court w i I 1 do so. This

element of foresight seems to exist in many cases where the plaintiff was not successfid

Part V - A Rationale for Cases Involving a Situation of Impossibility 72

in her claim, in spite of the situation of impossibility she confronted. For example in

WiZsher, if the negligent act of the hospital was in creating a risk of the development of

RLF in the premature phintiff, the fact that premature children are exposed to a variety of

conditions that may cause RLF must have been known to the defendant, as m u t the

difficulty for the plaintiff in distinguishing the cause of the condition if the plaintiff did

subsequently s d e r the injury. In these circumstances, if the defendant negligently

introduced another possibly negligent source, it does not seem difficult to Say that she

must have foreseen the difficulties the plaintiff may encounter in distinguishing that

cause fkom o t h e r ~ . ' ~ ~ Similady in Sindell. the reference in the decision to the use of

generic dmgs and the Iatency of the form of cancer they could cause, suggested to the

court the idea of foresight of the special problem of proof the plaintiff was likety to face.

So the idea of foresight on the part of the defendant seems to afEord a basis for saying that

the defendant is responsible for the situation of impossibiiity, and as between the plaintiff

and defendant, she should bear the consequences of the inability to prove causation.

However, it does not explain when a plaintiff will be successfUl in her claim in spite of

the situation of impossibility.

A third element that we identified in Our review was the relevance of the fact that the

ptaintiff may be able to show that she has suffered a wrongfül injury. or that the

defendant has inflicted a wrongfùl injury. The question again is whether proof of either

of these elements provides a reason for treating cases involving a situation of

impossibility differently from ordinary cases. and justifies a relaxation of the ordinary

requirement for proof of a causal relation.

This aspect is, perhaps, easier than the previous two we have considered. It is suggested

that the importance of these factors is clear. The reason proof that a plaintiff has suffered

'" This would, however, be a matter of evidence. [t may be that in the usual case the doctor would expect the cause of the RLF to be identifiable.

Part V - A Raiionait for Cases InvoIving a Siniation of Impossibility 73

a wrongfd injury is important in considenng these cases was made clear by Professor

Weinrib.

It might be objected that as between Cook v. Lavis and McGhee this is a distinction without

difference, that Cook v. Lewis allows for the possibility that the defendant who has breached a

duty of care might have to pay for an injury that he did not cause, and that it should not make any

difference to him whether the real cause is culpabte or innocent But the basic premise of tort law

has been not only to make the wrongdoer pay but also to compensate only those plaintiffs who are

the victims of a tort, There seems to be a significant leap between making whofe a plaintiff who

has suffered a tortious injury and allowing recovery to one whose injury might not otherwise fail

within the scope of tort law,

There is a certainty of doing an injustice if a plaintiff who has shown herself to be the

victim of a wrongful injury is not c ~ r n ~ e n s a t e d . ' ~ ~ This is not the case where the plaintiff

may only possibly have been the victim of a tortious wrong. In such a case. not only

would a defendant who may not have injured the plaintiff have to pay for the plaintiff s

injury, but that defendant may also be compensatïng a piaintiff who has not even suffered

an injury recognised by tort law. Where we know that the plaintiff has suEered a

wrongfiil injury, part of the uncertainty created by the situation of impossibility is

removed in that we know the plaintiff is one entitled to compensation-

The same is true of the possibility that the plaintiff may be able to show that the

defendant's negligent act has inflicted a wrongful injury. Just as tort law is not concemed

with injuries that are not wrongfiif, it is not concerned with wronghl acts that do not

cause injury. If a plaintiff can show that the defendant has wrongfully injured some

person, part of the uncertainty created by the impossibility of proving causation is

removed. We know that the defendant is required to compensate a plaintiff, albeit we do

not know whom.

12' Weinnb, mpra note 25 at 525.

130 Professor Williams, in reference to the decision in Cook v. Lewis, has noted: "To deny a remedy means that justice is certainly not done; to give a remedy would mean a fi@ per cent possibility that justice is done." G. L. Wiltiams, Case note, (1953) 3 1 Can. Bar. Rev. 3 15 at 3 17.

Part V - A Rationde for Cases Involving a Situation of [mpossibility 74

There is, however, a m e r issue that needs to be considered in this context, and that is

the relevance of the fact that al1 defendants (or aiternatively plaintiff s) are before the

c o u d 3 ' This was the case in both Corey v. Hmener and Cook v. Lewis. and it is a

point of distinction fiom a case such as Sindell. The presence of al1 possible defendants

before the court may illustrate more starkly that a 'guilty' defendant will escape liability.

However, it is suggested that this fact has no normative significance. As a simple matter

of logic and fairness, it would be an unusual rule that made liability dependent on the

pIaintiff joining the correct parties to the litigation. If our concem is in establishing the

basis on which an individual defendant can be held liable to the plaintiff (as the

traditional causal inquiry requires). it is difficult to see why the conduct of others (over

whom she has no control) or the decision of the plaintiff as to who to sue shouid

determine this LiabiIity. Where it is certain that a plaintiff has suffered a wrongful injury,

it is also certain that a defendant, somewhere. has inflicted that injury. Where it is certain

that a defendant has inflicted a wrongful injury, it is certain that a plaintiff somewhere

has suflered a wrongful injury. The significance of the point is that tort law. in those

circumstances, is focused either on compensating the victim of a tortious wrong or

making the inflictor of a tortious wrong pay. not that al1 possible causes of that wrong are

before the court.

However, that is not to Say that the fact al1 possible plaintiffs or defendants are before the

court is irrelevant. Rather, its significance is purely as a matter of practicality. I t rnay be

difficult for a plaintiff to show she is the victim of a tortious wrong if she has not joined

al1 possible defendants to the case. Because she must prove that al1 possible causes were

tortious to show a tortious wrong, if the other possible tortfeasors are not there before the

court, a court may be unwiliing to speculate as to the nature of their conduct when they

have not been heard frorn."' Likewise. if al1 possible plaintiffare not before the court, it

'3' This is the view put forward by CeIli. supra note 7 at 642.

13' Although, as the decision in Binda Mineper v. Barnes. supra note 1 16 shows, it is not irnposribk to show that the injury was a tortious injury when al1 defendant are not before the court. See also McAfIister v. The PennsyIvania RaiIroad Company, supra note 8 8,

Part V - A Rationale for Cases Involving a Situation of trnpossibility 75

may be difficult to show that the defendant h a injured some other plaintiff who is not

before the court,

Tlte Degree of Uncertainty of a Causal Relation

The final consideration that arose from our discussion of the case law in Part IV was that

of the degree of uncertainty of a causal relation. We saw earlier that there were three

possibilities in this r e g e it may be certain that the defendant's act at least contributed to

the pIaintWs injury, it may be uncertain whether the defendant's act contributed to the

injury. but it remains a substantial possibility that it did do so, and it may be uncertain

whether the defendant's act contributed to the injury, and any causal relation is in the

circumstances speculative. Here we consider the nature of this division, and in particular

the division between cases where there is a substantial possibility of a causal relation and

cases where such a relation is purely speculative. It will be suggested that this

consideration is hdamentally different fiom the three other ideas considered above.

Their focus was ultimately on why a court might treat cases involving a situation of

impossibility difTerently from other cases. The importance of the degree of uncertainty of

a causal relation asks a different question; given that there appear to be compelling

reasons for not allowing a plaintiffs claim to fail in cases involving a situation of

impossibility, how can this be done while still respecting the need for proof of a causal

relation? Simply put, the question is whether it is possible to maintain the integrity of the

causal relation in cases involving situations of impossibility?

The easiest response to this question is in cases involving certainty of contribution. In

those cases there is vindication of the causal relation because it is clear that a causal

relation in some sense exists. The question there is whether the defendant's act, which

was clearly a cause of the injury to the plaintiff. should be regarded as the cause for the

purposes of imposing liability. Here the potential for an unenforceable duty, the idea of

fault on the part of the defendant in foreseeing the situation of impossibility. or the fact of

certainty that the plaintiff has suffered a tortious injury, could al1 provide a b a i s for

accepting a lesser standard of proof of a causal relation as sufficient for imposing

Part V - A Rationale for Cases Involving a Situation of ImpossibiIity 76

liability. In doing so, the court wouid still vindicate the need for proof of a causal

relation. The more difficult question is how to vindicate the existence of a causal relation

where there is no certainty of contribution. and the possibility of a causal relation is

simply that, a possibility. It will be suggested that the analysis of the cases in Part IV

shows that where a plaintiff is able to show at a minimum proof of a substantial

possibility of a causal relation, there is vindication of the requirement for proof of a

causal relation. To show the strength of this approach, it will be contrasted with two

separate approaches that have also claimed to vindicate the importance of the causal

relation in such cases; namely an approach that reverses the burden of proof, and an

approach which aliows the court to infer a causal relation.

Substanfial Possibiliry of Cause in Fact vs. Spectttution

In a case involving a situation of irnpossibility. where there is uncertainty of cause (that

is, cases in categories 3 to 6), the existence of a causal relation is a fact that will never be

known. If it codd be, then there already exists mechanisms for dealing with the

evidential gap, such as the process of drawing inferences for failing to produce evidence

that were referred to in Part III. It follows. therefore, that if a defendant is to be made

Iiable for the loss suffered by the plaintiff, it will always remain a possibility that she did

not in any way cause the injury for which she is being held liable. The question is

whether this possibility should mean that in every case involving a situation of

impossibility, the plaintiffs claim must necessarily fail. 1s there a way that the plaintiff

can succeed while still vindicating the idea of a causal relation, or does a situation of

impossibility nccessarily require the abandoning of the requirement for proof of a causal

relation?

It is suggested that the idea of a substantial possibility of a causal relation does vindicate

the need for proof of a causal relation to the extent that such proof is possible in these

cases. While the existence of a causal relation cannot be known with what the Law treats

as certainty, we are still able to evaluate the possibility of such a relation existing. Indeed

that is al1 that c m be known. If we are still concemed with the existence of a causal

Part V - A Rationale for Cases Involving a Situation of Irnpossibility 77

relation the only question we can ask is what is the possibility of such a relation existing.

In looking to the possibility of such a relation, we are still making the causai relation the

focus of our inquiry, while recognising that its existence can never be known.

If this approach is correct, then the distinction between cases where such a causal relation

is a substantial possibility and those where it is a matter of speculation is easily

understood. Where such a relation is a substantial possibility, there is vindication of the

causai relation because while we can never know whether the act of the defendant was a

cause of the plaintiffs injury, it remains a realistic alternative on the known facts of the

case. There is reason to believe that if al1 the facts were known, the defendant's act

would be found to have been a cause of the injury. However, where such a relation is

pure speculation, the requirement for proof of a causal relation is vindicated by not

imposing Iiability on the defendant. ïhere is in such a case no realistic possibility that if

al1 the facts were known, the defendant would be found to have been the cause of the

i n j ~ r y . ' ~ ~

This analysis reflects the distinction between cases in categories 3 and 4 and cases in

categories 5 and 6, as was illustrated in the review of the cases. Cases in al1 categories

raised issues of policy such as those considered above. However, what appeared to be

determinative of the cases was that in cases in categones 3 and 4 there remained a

substantial possibility that the defendant caused the plaintiff s injwy, while in cases in

categories 5 and 6, such a possibility seemed to be a matter of speculation. The idea of a

substantial possibility of a causal relation both explains the difference between these two

groups of cases, and does so in a principled manner. Where the plaintiff is able to show a

substantial possibility of a causal relation between the defendant's negligent act and her

injury, she does the best that can be done in a case where it is impossible to positively

prove such a relation. In requiring at the minimum proof of such a possibility. the court

133 This analysis wouId also explain the gloss that was placed on the decision in McGhee, in respect of the idea of injury within risk king suficient for a prima facie case of causation, that this would only apply if in the circumstances of the case, the risk was so great that the defendant was "certainly asking for trouble". See Nowsco Weil Services v. Canadian Propane und Cas & Oil, supra note 107 at 246 per Bayda J-A-.

Part V - A Raîionale for Cases Involving a Situation of trnpossibility 78

is still focusing on the need for a causal relation. not abandoning it in favour of broder

policy grounds.

Reversing the Burden of Proof

An alternative way that has been suggested of vindicating the requirement for proof of a

causal relation in cases involving a situation of impossibility is to reverse the burden of

proof, and make the defendant show that she did not cause the injury to the plaints.

This approach is best summarïsed by Professor Weinnb whea in reference to the United

States case of Summers v. Tice (a case identical to Cook v. Lewis). he stated: "To the

extent that these cases still allow defendants to exculpate themselves by disproving their

causal role, they merely modifjr the evidentiary mechanisms regarding causation without 0- 134 negating its systemic importance for tort liability:' The important words here are the

first part of the sentence, as the vindication of the causal relation is in the abiIity of the

defendant to disprove the causal relation if abIe. The problem with this approach is that it

is just this ability that is at issue in cases involving a situation of impossibility.

It is true that the burden of proof is not immutable. and that in a nurnber of well known

exceptions, the courts will place the burden of proof on the defendant.'35 Yet in those

limited cases where the burden of proving causation has been moved to the defendant, the

causal relatiooship is still vindicated either because of the inference of fact that c m be

drawn from the failure of the defendant to disprove causation (for example where the

defendant h a , or should have, better knowledge of the circumstances relevant to the

issue of causation), or because the plaintiff has already established a prima facie case of

'% Weinrib, Private Law, supra note 13 at 154 - 155.

13' For example, in bailment cases the usual rule is that if a chatte1 was damaged while in the bailee's possession, she mua prove that the loss was not occasioned by her negligence. This reversal of the burden of proof is made on the assumption thar the baiIee is in a better position to know what happened to the chatte1 than the bailor, although this reversal can itself be dispked if that assumption is not justified on the facts of the case. See Narional Ti-usf Company v. Wong Aviation (1969) 3 D.L.R. (36.) 55 (S.C.C.). in actions for breach of fiduciary duty and for negligent misstatement, it is the defendant who must disprove the assumption that the plaintiff would not have suffered the loss if the statement had not been made or the breach of fiduciary duty commiîted. See Rainboiv Indurrial Caferers Y. Canadian National Railway (1991) 59 B.C.L.R. (2d.) 129 (S.C.C.); Hodgkimon v. Simms 119941 W.W.R. 609 (S.C.C.).

Part V - A Rationale for Cases lnvolving a Situation of impossibility 79

causation, and the argument put forward by the defendant amouats to a positive defence-

In contras& on this approach, the reason that the burden is reversed in cases involving a

situation of impossibility is because it is impossible for the plaintiff to prove the existence

of a causal relation. It must also, therefore. be impossible for the defendant to disprove

such a relation, and so the vindicating possibility referred to by Professor Weinrib does

not exist, Without this possibiiity. reversing the burden of proof becomes simply the

mechanical response to the broader policy concerns cases involving a situation of

irnpossibility create.

This is not to Say that reversai of the burden of proof may not ultimately be the way to

implernent any decision on how cases involving a situation of irnpossibility are to be

resolved. The point is that it does not. in itself. in anyway affium the importance of the

need to prove a causal relation. Where it is not possible for either party to discharge the

burden, it can only be a method by which some pnor decision on the issue of who should

bear the responsibility for the situation of impossibility is implemented. By contrast, the

approach that has been suggested of a substantial possibility of such a causal relation still

places primacy on the factual aspect of the causal inquiry. It does not leave the question

purely one of policy, but maintains some standard at least of factual causation.

A second approach that has sought to vindicate the requirement for proof of a causai

relation in cases involving a situation of impossibility has been to use a 'robust' and

'comrnon sense' approach to ca~sation."~ On this approach, when a court is confionted

with a situation of impossibility, it will infer a causal relation (although with the

possibility remaining of the defendant displacing the inference, if able). This is perhaps

the dominant approach to such cases, yet it is one which it is suggested is fimdarnentally

flawed. It involves the irreconcilable contradiction that the court infers causation (and

therefore treats it as proved) in cases where by definition such a relation is impossible to

prove. It is, as with the approach which reverses the burden of proof, an assertion of

136 See, for example, Snell v. Farrell. supra note 8.

Part V - A Rationale for Cases InvoIving a Situation of Impossibility 80

liability based on a broader evaluation of the policy issues involved, while ignoring the

importance of the causal inquiry to tort law.

The problems with this approach can be well illustrated by decision in Dalphe v. City of

~dmun«on.'~' The plaintiffs basement flooded as a result of an overflow in her

sewerage system. The drain had become blocked by a stick, which in tum caused a

backiog of other materiai. The defendant was responsible for the maintenance and

inspection of the sewerage system. and was under a duty to regularly inspect it for such

blockages. The last time it inspected the sewerage system on the plaintiffs Street was

one year prior to the incident, and the court held that if an inspection at that tirne had

shown the drain to be clear, the defendant would have discharged its duty. However, the

defendant did not inspect the drain at that time because the dosest man-hole cover had

been covered during earlier road repairs. The problem for the plaintiff was that on the

evidence of the expert witnesses. it was impossible to tell when the stick had lodged in

the grate. It could have been I day or 1 year before the flood. Therefore it was

impossible to Say whether the failure to inspect the drain was in anyway causative of the

overflow in the sewerage system.

In spite of this situation of impossibility. the court \vasi prepared to infer a causal relation

between the failure to inspect and the injury to the plaintiff. While the decision in this

case could well be jded on the ba i s of a substantial possibility of a causal relation

discussed above, it is diEcult to see any bais on which it could be said that a positive

causal relation could be inferred. To prove a causal relation, the plaintiff would need to

show that the stick would have been there 1 year previously so that inspection by the

defendant should have revealed it. But this was the very thing on which the facts were

inconclusive.

This is not to say that when confronted with what appears to be a

impossibility the court should not be prepared to be more aggressive

situation of

in inferring

13' 25 N.B.R (2d-) 103 (N.6.S.C). Affirmed by the S.C.C. in Snell v. Farrefl. supra note 8

Part V - A Rationale for Cases Involving a Situation of Impossibility 8 1

causation than it might otherwise be. For example, the apparent situation of hpossibility

in Letnik was resolved by an inference of ca~sa t ion . ' ~~ If a ship has been at its mooring

for 12 years without sinking, then sinks two weeks f i e r king struck by the defendant, it

seems a reasonable inference that the sinking was caused by the coiiision. But these

cases would not then be cases involving a true situation of hpossibility. Rather the facts

permit an inference of causation to be dnwn. The impression Dalphe and similar cases

give is that the inference that is drawn is not based on facts relevant to the issue of

causation, but rather by the broader policy concerns raised by a situation of

i~n~ossibii i ty. '~~ If this is correct then the ûpproach is ultimately no ditferent Born that

which reverses the burden of proof. It is simply a response to a situation of impossibility

that in no way recognises the importance of a relation of cause-in-fact.

13' Supra note 51. Other examples of this 'robust' ultimatety based on inferences fiom primary facts, Georgetown S h i ~ a r d s (1995) 123 Nfld- & P.E-1.R 91 24 C.C.L.T. 6 (B.C.CA); Amunaken v. Ward (19 13) 1 I

approach to drawing inferences. but one that is are Canada (Attorney General) v. Chrey and

( S C ) : Delaney v. Cascade River HoMays (1 983) D.L.R. 167 (Alta- S C ) .

139 This approach is perhaps ben illusmted by the decision in Snell v. Farreil, supra note 8. In that case. Sopinka I. explained the b a i s on which the inference o f causation was drawn in the following terms (at 305): "The appellant was present during the operation and was in a better position to observe what occurred. Furthemore, he was able to interpret fiom a medical standpoint what he saw. In addition, by continuing the operation which has been found to constitute negligence, he made it impossible for the respondent or anyone else to detect the bleeding which is aIleged to have câused the injury. In these circumstances it was open to the trial judge to draw the inference that the injury was caused by the retro- bulbar bIeeding."

Part VI- Conclusion

PART VI - CONCLUSION

Proof of causation in the law of negligence is a fimdamental requkment for establishing

the entitlement of a plaintiff to compensation and the Iiability of a defendant to

compensate. Cases involving a situation of impossibility appear to challenge the

fundamental nature of this requirement because in many cases the plaintiff has been able

to recover even though she has been unable to prove that the negiigent act of the

defendant caused her injury. The reason the courts have allowed a plaintiff to recover in

such cases is often difficult to identie. There has been a cl- reluctance to recognise the

problem the plaintiff confiants, with courts choosing to focus instead on policy reasons

for shifting the burden of proof, or its ability to robustly infer a causal relation- This

reluctance to confkont the problem faced by thc plaintiff has nieant that many cases

involving a situation of irnpossibility are resolved on the ba i s of the simple comparative

assessrnent that as between an innocent plaintiff and a negligent defendant. the defendant

should bear the plaintiff s los . In such cases, the need for proof of a causal relation is al1

but abandoned.

This paper has sought to identi@ what it is about cases involving a situation of

impossibility that separates them fiom the usual case where a plaintiff fails to prove

causation, and what it is that determines when a ptaintiff will succeed in such cases. The

paper suggested that there are three broad issues of policy that may arise in cases

involvïng a situation of impossibility; the creation of an unenforceable duty. a defendant

who is responsible for the a situation of impossibility escaphg liability, and a failure

either to compensate a plaintiff who has suffered a wrongful injury or for a defendant

who has inflicted a won@ injury to compensate. The presence of these factors forms

the policy basis on which courts are prepared to fmd for a plaintiff in such cases.

However, in the face of these policy concerns, the courts have not simply abandoned the

requirement for proof of causation. The decisions can be read as still insisting on proof

of a causal relation to rhe extent rhat rhis is possible. They have ailowed a plaintiff to

succeed ody if she can show that the defendant's negligent act contributed to her injury,

or there is a substantial possibility that it did so.

Part VI- Conclusion

This paper is at best a preliminary consideration of the difficult issues involved in these

cases. Its value is ultimately in i d e n m g what it is that is distinct about cases involving

a situation of impossibility, the exact nature of the policy concerns that &se in these

cases, and in dispelling some of the misconceptions that surround the various approaches

that have k e n taken to these cases. The discussion has k e n limited to the accepted

principles of compensation in tort Iaw, and in particular the need for proof of a causal

relation and the al1 or nothing approach to compensation. The paper has suggested a way

in which the cases can be understood that attempts to vindicate the need for prmf of a

causal relation in negligence. Perhaps the biggest question that remains to be considered

after this paper is whether a plaintiff, given the uncertainty that must exist in such a cases,

should still be entitied to fùll compensation.