Editorial

Human DNA contamination of mortuaries: does itmatter?

G. N. Rutty*Department of Forensic Pathology, Medico-Legal Centre, Shef®eld, S3 7ES, UK

*Correspondence to:G. N. Rutty, Department ofForensic Pathology, Medico-LegalCentre, Watery Street, Shef®eld,S3 7ES, UK.E-mail: G.N.Rutty@Shef®eld.ac.uk

Received: 10 September 1999

Accepted: 28 September 1999

Abstract

With the continuing development of extremely sensitive, automated systems for the detection of

human DNA from a number of cellular sources, the problem of sample contamination from scenes

of crime, cadavers, and the mortuary environment has become a potentially serious issue, with

implications for all involved in forensic investigations. A recent survey of 20 mortuaries identi®ed

quanti®able human DNA on mortuary work surfaces and instruments which, when ampli®ed,

produced in some cases three or more pro®les from single site samples. Possible sources of DNA

contamination in the mortuary are discussed, along with implications related to its presence and

its avoidance during the sampling process. These observations may not be con®ned to forensic

practice. Copyright # 2000 John Wiley & Sons, Ltd.

Keywords: human DNA; mortuary; instruments; contamination; DNA ®ngerprinting; forensic

In the last 14 years, since Gill ®rst highlighted theforensic applications of DNA `®ngerprinting' in 1985[1], the analytical techniques used to identify humanDNA have undergone signi®cant development. Fromthe original multilocus probes (MLPs), through to thesingle locus probes (SLPs) and short tandem repeats(STRs), the techniques have become quicker and moresensitive, with sample sizes becoming ever smaller.These techniques now play a major role in bothdiagnostic and research work in hospitals, universities,and industry throughout the world. Within the area offorensic investigation, the search for the identi®cationof the offender's or victim's DNA, be it nuclear ormitochondrial, has led to the development of extremelysensitive automated systems, potentially able to detecthuman DNA from a wide range of cellular sources andthen cross-reference the pro®le against an ever-growingdatabase [2,3].

However, as with any technology, there is always adrawback; in this case, the more sensitive the tech-nique, the greater the problem of contamination.Although this has been recognized by researchers formany years [4], until now it has not been considered asigni®cant problem for those working within theforensic ®eld. Recently, however, in two areas of theUnited Kingdom, human DNA pro®les from samplessubmitted following autopsy procedures were found tohave originated from mortuary instruments which hadbeen contaminated by cadaveric DNA (personal andHome Of®ce communications). A larger study per-formed by the author revealed that of 20 mortuariesexamined, 50% had quanti®able human DNA on oneor more instrument, cutting area or mortuary table.When these were ampli®ed, they gave at least onehuman pro®le and in some cases, at least three pro®leswere detected from single sample sites, usually large

scissors. In the case of swabs from which no quanti®-able result could be obtained, a random selection were,however, still ampli®ed and partial pro®les weresubsequently identi®ed in a signi®cant number.

Are these ®ndings surprising and do they matter?The answer to the ®rst question is regrettably no. It isan unfortunate state of affairs that many UK mor-tuaries are dirty and/or ill equipped. Comments havebeen published previously by those who visit morethan one mortuary as part of their job that adequateprotective clothing, dissecting instruments, weighingfacilities for whole bodies or organs, and facilities foradditional investigations are in some cases woefullylacking [5]. Many of these pathologists have to carry`mortuary kits' around with them to perform anadequate investigation. At times, blood may be clearlyvisible on supposedly clean instruments or surfaces,but even if the majority of work surfaces andinstruments do appear `clean' to the naked eye, thestudy referred to above illustrates clearly that this maynot be the case.

If human DNA is identi®ed from either a scene ofcrime or a sample obtained from a mortuary, thesource may need to be identi®ed. This is an expensiveand time-consuming exercise. In the mortuary setting,there are ®ve potential sources for the origin of thisDNA, not to mention the possibility that it could havearisen from the inside of the body bag, which may havebeen used previously to carry another cadaver andthen `cleaned' out, a common practice in some areas ofthe country.

The ®rst possibility is that the DNA has originatedfrom cells of the deceased which have contaminatedthe exhibit during the sampling process, particularlyduring ®ngernail sampling. As a control sample of thedeceased's DNA will also be acquired at the autopsy,

Journal of PathologyJ Pathol 2000; 190: 410±411.

Copyright # 2000 John Wiley & Sons, Ltd.

usually blood or muscle, the origin of the contaminantcan easily be identi®ed by cross-checking with thecontrol sample.

The second potential DNA source is the pathologist.Contamination could arise from a number of singlecell sources shed by the pathologist whilst takingexhibits from the cadaver, which could include cough-ing or sneezing over the sample area. Most individualscurrently working in the mortuary do not wear masks,visors or hats, although the majority do wear at leastone pair of gloves.

The next source could be the mortician. Just becauseeverybody else may be wearing gloves during theautopsy does not exclude the possibility that themortician may have handled an instrument prior tothe autopsy with his or her bare hands, thus poten-tially contaminating it. The identi®cation of DNApro®les from those handling inanimate objects withoutwearing gloves, for example from steering wheels inautomobile-related crime, is a rapidly expanding ®eldof forensic science. This and the previous source will bedif®cult to identify, since currently most morticians,pathologists, and even the police of®cers and theirallied workers do not have their DNA pro®les on thedatabase for exclusion purposes.

Of signi®cance to the investigating of®cers is thepotential to identify the DNA pro®le of a third partyrecovered from the cadaver, i.e. a potential offender.Such material may be found at several sites on thebody and its retrieval may require speci®c samplingtechniques.

The ®nal potential source of DNA, which untilrecently has not been seriously considered, is contam-ination of instruments or work surfaces from pre-viously autopsied bodies. As this source of DNA mayhave been either buried or cremated, this will producean unidenti®able pro®le.

Thus, the answer to the second question is yes, itdoes matter. Human DNA derived from mortuaryinstruments or surfaces may lead to a fruitless, time-consuming, and expensive search for a third party thatdoes not exist. Also, and potentially more important,as human DNA pro®les are to date not unique, there isa defence that the pro®le which was isolated from amortuary-derived sample and which may subsequentlybe used to assist in a conviction of a crime may havearisen as a result of a contaminant from the mortuaryitself.

The UK Home Of®ce and Association of ChiefPolice Of®cers (ACPO) view this potential problem soseriously that they recommend, whenever possible, theuse of brand new, clean, disposable instrumentswhenever a sample is taken which may be requiredfor DNA testing. However, responsibility for theimplementation and cost of such a policy variesthroughout England and Wales.

It is therefore evident that just because one cannotsee any body ¯uids or cells on the instruments or worksurfaces does not mean that they are not contaminatedby human DNA. The use of sterilizing solutions andeven autoclaves does not exclude the possibility ofDNA contamination; moreover, some manufacturersof disposable instruments, when asked, allegedly couldnot guarantee that the instruments supplied would infact be DNA-free, which, if true, defeats the point ofgoing to the trouble of using such instruments(personal communication).

These observations are not just important in the ®eldof forensic investigation, but could affect anyonereusing equipment or instruments in his or her dailywork, for example in laboratory research, as well as insurgical or dental practice. Although the use ofdisposable instruments or the taking of control instru-ment swabs in part addresses the problem, we shouldreconsider the whole question of equipment, protectiveclothing, and cleanliness in our mortuaries, labora-tories, hospitals, and dental surgeries. With regard tomortuaries used in forensic work, one solution for thefuture could be to centralize these services in properlyequipped, regional accredited `DNA-free' mortuaries.

References

1. Gill P, Jeffreys AJ, Werrett DJ. Forensic applications of DNA

`®ngerprints'. Nature 1985; 318: 577±579.

2. Kimpton CP, Gill P, Walton A, Urquhart A, Millican E, Adams

M. Automated pro®ling employing multiplex ampli®cation of

short tandem repeat loci. PCR Methods Appl 1993; 3: 13±22.

3. Oldroyd NJ, Urquhart A, Kimpton CP, et al. A highly

discriminating octoplex short tandem repeat polymerase chain

reaction system suitable for human individual identi®cation.

Electrophoresis 1995; 16: 334±337.

4. Lee HC, Ladd C, Scherczinger CA, Bourke MT. Forensic

applications of DNA typing. Part 2. Collection and preservation

of DNA evidence. Am J Forensic Med Pathol 1998; 19: 10±18.

5. Williams AR. Health and safety in the mortuary. ACP News 1998;

43±44.

Human DNA contamination of mortuaries 411

Copyright # 2000 John Wiley & Sons, Ltd. J Pathol 2000; 190: 410±411.