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  • 10.1192/bjp.163.5.565Access the most recent version at doi: 1993 163: 565-573 The British Journal of Psychiatry

    P Fenwick

    Brain, mind and behaviour. Some medico-legal aspects

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  • British Journal of Psychiatry (1993), 163, 565573

    Psychiatry is changing in a significant way, as newimaging techniques are helping to answer questionsabout the relationship of brain to mind, consciousnessand behaviour. Knowledge of the neurotransmitterchanges which underpin pathological brain states isincreasing, and it seems possible that before the endof the century much of the pathology of the majorpsychiatric illnesses will be understood. This will leadto a clearer understanding of the relationshipbetween brain pathology and the impulsive behaviourthat leads to violent crime, which will have importantimplications for the development of the law.

    Mensrea'

    It is a fundamental tenet of English law that,providing the mind is sane and the person not underduress, everybody of the age of discretion is presumed responsible for his actions. Actus non facitreum nisi mens sit rea thedeed doesnot make a manguilty unless his mind is guilty'. Unless the offenceis a statutory one which carries an absolute liability(e.g. driving with a raised bloodalcohollevel), thepresence of a guilty mind can be negated by threemajor considerations (as well as the defences ofduress and provocation). The first defence is that themind is innocent, and does not know the differencebetween right and wrong. Mental subnormality canfall into this category, but is seldom used as a defenceas there are mental health statutes which arepreferable.

    The second defence is that the mind is diseased.This is the defence of insanity, and is dependent onthe McNaughton rules: that is, atthe time of thecommitting of the act the party accused waslabouring under such a defect of reason, from disease

    This paper is based on the St George's Hospital Curran Lecture1991.

    of the mind, as not to know the nature and quality ofthe act he was doing, or if he did know it, that hedid not know he was doing what was wrong.

    The third defence is that the mind is absent automatism'.Here the law enters a quagmire intowhich, it has been said, only a man in desperate needof some sort of defence will venture. There are twotypes of automatism in law: sane and insane. Saneautomatisms are due to external factors a bee-stingon the arm causing a reflex action, concussion aftera blow on the head impairing mental function, orhypoglycaemic confusion and bizarre behaviourfollowing injected insulin, are all examples ofautomatisms due to external factors. Insane automatisms are due to an inherent internal cause.Cerebral tumour, arteriosclerosis, an islet-cell tumourof the pancreas, or epilepsy, are all internal factorswhich may lead to automatic behaviour in a confusional state. A defendant found not guilty due tosane automatism walks free from court, whereas averdict of not guilty due to insane automatism, untilrecently, led to a mandatory referral to hospital,often a secure hospital (Fenwick, 1990a). However,since the Criminal Procedure (Insanity and Unfitnessto Plead) Act 1991, there is no longer a mandatoryrequirement that a person found to be insane beadmitted to hospital, as the judge can decide ondisposal.

    The distinction between sane and insane automatisms makes little medical sense. It is difficult toargue, for example, that the confusional state fromthe insulin secreted by an islet-cell tumour is anydifferent from the confusional state produced byinjected insulin. The reason for the distinction isclear. The lawyers are concerned with the protectionof society, and therefore with the likelihood ofrecurrence of a violent act. The medical profession,however, is also concerned with the possibletreatment of the patient so as to avoid recurrence,

    565

    Lecture

    Brain, Mind and BehaviourSome Medico-legal Aspects

    PETER FENWICK

    The advent of new imaging techniques is broadeningour understandingof the major psychiatricillnesses. The increased knowledge of brain function will have consequences for the expertmedical witness who has to give evidence in court. Both the insanity defence and the defenceof automatism depend on disorders of the mind. Psychiatry is now able in many cases toproduce evidencethat these areconsequentupon disordersof the brain. In presentingevidencein court there is an apparent conflict between brainwords' and mindwords'.

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  • 566 FENWICK

    so the aetiology and pathology of the confusionalepisode are all-important.

    Brain, mind and automatism

    To reach its present position on insanity andautomatism the law has had to refine the differencebetween brain and mind. It was easy to argue fromthe McNaughton rules that schizophrenic or depressedpatients who were deluded or hallucinated did notknow the nature and quality of their actions or, ifthey did, that they did not know what they weredoing was wrong. It was clear that when violence wascommitted in these circumstances, the offendershould be treated in a secure hospital. However, ifviolence were due to an organic process whichtemporarily distorted the functioning of the mind,the position was less clear. The case of R. v. Charlson(1955) illustrates this. The defendant was standingat a window of his house which overlooked a river.He called to his young son and pointed out to hima rat sitting on a stone. He then picked up a woodenmallet, struck his son several times on the head, andthrew him through the window. Charlson thenwandered out of the house and, when detained a fewminutes later by a policeman, said he felt he had donesomething awful but could not remember what itwas. Charlson was found to have a cerebral tumour,and was acquitted on the grounds of sane automatism; cerebral tumour is not a disease of the mind.

    This was a clear statement that brain (tumour) andmind are separate. If this view had held, it wouldbe theoretically possible to argue in court thatautomatisms arising from diseases of the brain weresane, and a sufficient defence. The advances inimaging would make such a defence not only easierbut also, probably, popular. For example, it wouldbe quite logical now for schizophrenia to be put intothe category of diseasesof the brain' rather thatdiseasesof the mind'; if this were upheld in court,schizophrenic people committing violent acts wouldautomatically have to be released.

    Even more contentious would be the use ofabnormal magnetic resonance imaging (MRI) scansto provide a defence of sane automatism in patientswith minimal brain damage who showed impulsiveand potentially dangerous behaviour. Clearly, as theligands used in positron emission tomography (PET)scanning become more refined, receptor function willbe more clearly demonstrated. As the mechanismsof behaviour become better understood, it maybecome apparent that many impulsive acts coulddepend on receptor changes and therefore result fromdisease of the brain. This would then allow thedefence of sane automatism, leading to automatic

    acquittal. A recent article points to the dangers ofover-interpreting imaging data in court (Mayberg,1992).

    The case of Kemp

    This danger was foreseen in the case of R. v. Kemp(1957, 1956). Kemp seriously injured his wife, withwhom he had an excellent relationship, in amotiveless attack with a hammer. It was acceptedthat when he attacked her he was in a confusionalstate due to arteriosclerosis, a disease of the brain.Kemp thus wished to plead sane automatism. LordJustice Devlin disallowed this, saying that the properplea was insane automatism. He said:

    Thelaw is not concernedwith the brain but with themind, in the sense that mind is ordinarily used, themental facultiesof reason,memoryand understanding.If one read for diseaseof the mind' diseaseof thebrain', it would follow that in many cases pleas ofinsanity would not be establishedbecauseit could notbe proved that the brain had beenaffected in any way,either by the degenerationof the cellsor in any otherway. In my judgement, the condition of the brain isirrelevantand so isthequestionof whetherthe conditionof the mind is curable or incurable, transitory orpermanent. There is no warranty for introducingtheseconsiderationsinto the definition in the McNaughtonrules. Temporary insanityis sufficientto satisfy them.It doesnot matterwhetherit is incurableand pennanent,or not.

    This case raised two interesting points: the ideaof treatability, and the question of length of time ofimpairment. Justice Devlin was very clear that bothtime and treatability were irrelevant, and did notaffect the application of the McNaughton rules.Kemp was duly found insane.

    The question of time was raised again in the caseof Bra