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Laws of England and Wales Essay

“The defendant who seeks to avoid criminal liability on the basis that s/he was suffering from a mental disorder at the time of the alleged crime must have a defence that falls within one of the following, legally recognised, categories: Insanity, Diminished Responsibility or Automatism. While, at one level or another, these “mental disorder defences” share common characteristics, they each differ significantly. Unfortunately, this point does not appear to be fully appreciated in English Law.”

Discuss the validity of this statement.

Inherent in our legal system is an idea of culpability. The word itself embodies notions of moral responsibility and blame. There are two elements that will allow us to determine whether or not someone is to be considered culpable. The first is that the person on whom we wish to apportion blame is an actual agent of harm as opposed to a mere causer. That is to say that they are instrumental in an action and are not simply a victim of a spasm or similar associated condition. The second is that he/she has the capacity to understand the laws and moral order that exist within society. Hart’s principles of justice assert that ‘a moral license to punish is needed by society and unless a man has the capacity and fair opportunity or chance to adjust his behaviour to the law, its penalties ought not be applied to him.”

Such deep-rooted notions of culpability have necessitated development in the area of defences to ensure that those who fall outside of the legally recognised parameters of accountability are afforded ‘protection’. Amongst such defences are Insanity, Automatism and Diminished responsibility. This essay will identify the similarities and differences of these defences by exploring their theoretical foundations and determine whether, in practice, they are sufficiently understood by the courts to achieve their desired end.

The theoretical basis for an insanity defence is embedded in the notions of fair opportunity as discussed above. It is felt that the insane man is ‘too far removed from normality to make us angry with him’. The impetus of the law and its functions might well be considered outside of his comprehension and similarly, so too might the moral implications of his act. Therefore, it would not be either ‘efficacious or equitable’ to hold such a man criminally responsible . As Duff remarks of the potential insane defendant “if she cannot understand what is being done to her, or why it is being done, or how it is related as a punishment to her past offence, her punishment becomes a travesty?”. Therefore, if a defence of insanity is successful the defendant will be given a ‘special verdict’ namely ‘not guilty by reason of insanity’. Although this special verdict may bring indefinite detention (a fact which is reconciled in theory by ‘compelling considerations of public interest’ ) it still serves to reflect a lack of culpability and therefore, blame.

The basis on which the non-insane automatism defence is founded is somewhat more fundamental than that of insanity. It was developed to exculpate those who had been the victim of events rather than those who had fallen foul to circumstance . A plea of automatism is ‘not merely a denial of fault, or of responsibility. It is more a denial of authorship’ in the sense that the automaton is in no way instrumental in any criminal act. Lord Dilhorne remarked in Alphacell that “an inadvertent and unintended act without negligence? might be said, not caused’. Others have described such acts as ‘acts of god’. It is with this class of act that the defence of automatism is concerned – acts which might be said seen as ‘inconsistent with the requirement of an actus reus’ . This lack-of-instrumentality concept is reflected by the fact that on a finding of automatism a defendant will be granted an unqualified acquittal by the courts. Detention is unnecessary for as well being blameless, the automaton presents no future threat to society.

Whilst Insanity and Automatism serve as general defences in law, Diminished responsibility operates only as a defence to murder. It offers those ‘bordering on insanity’ the opportunity to argue that at the time of the killing they were ‘suffering from such abnormality of mind’ so as to ‘substantially impair their mental responsibility’. If such an argument is successful (all other things being equal) the potential murderer will be convicted of manslaughter and hence will escape the mandatory life sentence that a finding of murder brings. The defence’s existence is justified (much like insanity) by notions of responsibility and blame. The doctrine, it was felt, ‘was needed to reflect the view that where there was less responsibility there ought to be less punishment.”

Despite some clear differences in the three defences’ theoretical foundations and intentions, it could be said that technically they have become somewhat confused in law. Discussion will now turn to the two automatism defences before then going on to examine diminished responsibility in context.

Whilst both automatism defences are grounded in the idea that ‘where there is no responsibility there should be no blame,’ policy reasons have necessitated their independent development. Because of this, the person who seeks to raise automatism as a defence is subject to a very tight definitional distinction. This tight definitional distinction between automatism and insanity is highlighted by Glanville Williams when he describes non-insane automatism as ‘any abnormal state of consciousness….while not amounting to insanity.’ Such statements offer little definitional worth, as to understand automatism we must first understand insanity and this, as will become clear, is no easy task.

The contemporary framework of the insanity defence can be found in M’Naghten’s Case where Lord Tindal authoritatively ruled that?:

“?to establish a defence on the ground of insanity, it must be clearly proved that, at the time of the committing of the act, the party accused was labouring under such a defect of reason, from disease of the mind, as not to know the nature and quality of the act he was doing; or, if he did know it, that he did not know he was doing what was wrong.”

Subsequent development of a non-insane automatism defence, for reasons discussed above, necessitated judicious refinement of these insanity parameters to insure that those who sought to invoke the former were deserving . Therefore, considerable onus was placed upon the meaning of the rules, especially the phrase ‘disease of the mind’.

First, it was decided that ‘mind’ referred to the mental faculties of reason, memory and understanding and not simply the organic mass that is the brain. Then, in Sullivan, (the defendant was charged with assault which, he claimed, was the result of the post-ictal stage of an epileptic seizure) the definition expanded to catch transient and intermittent impairment of the mind. It was held that the permanence of a disease ‘cannot on any rational ground be relevant to the application by the courts of the M’Naghten rules’. This finding ran contrary to contemporary medical definitions and began to impinge upon the design of the non-insane automatism defence: that being to catch one-off, faultless incidents of automatism.

Perhaps more significantly, Sullivan continued to develop Quick on what is now thought to be the defining boundary between the two defences, that of internal and external causes. This distinction was cemented in Burgess where Lord Lane explicitly referred to the difference between internal and external causes as the point on which the ‘case depends, as others have depended in the past’ The defendant in Burgess was a sleepwalker who assaulted a friend whilst in a somnambulistic state. It was held that somnambulism was a disease of the mind under the M’Naghten rules largely because it was considered a ‘pathological’ (and therefore, internal) condition by expert witnesses in cross-examination.

While, to some, this internal/external distinction ‘makes good sense,’ to others its effect is wholly inappropriate, as it fudges the boundaries between the theoretical rationales of insane and non-insane automatism. Irene Mackay, for example (as well as pointing to contradictory obiter ) attacks the distinction with reference to its effect. She contends that sleep ‘can hardly be called an illness, disorder or abnormal condition. It is a perfectly normal condition.’ Of interest here, Graham Virgo points to anecdotal evidence that cheese might cause sleepwalking. If such evidence could be substantiated, the somnambulist could potentially escape a special verdict by virtue of the fact that eating cheese would be considered an external cause. Such a consideration is far from easily reconcilable with the aforementioned notions of blame and responsibility as expounded by Hart’s principles of justice.

Mackay continues to attack Burgess on a second defining point. She contends that the court failed to properly adopt the definition of ‘disease of the mind’ as put forward by Lord Denning in Bratty – namely that it is “any mental disorder which has manifested itself in violence and is prone to recur.” Considering statistical evidence showing that no one had ever appeared before a court twice charged with somnambulistic violence, Mackay remarks ‘something which is prone to recur must be at least ‘inclined to recur or have a tendency to recur or be to some extent likely to recur.’ Despite such protestations, current medical opinion is that sleepwalking is caused by internal factors and may be likely to recur . Therefore it is suitable for M’Naghten insanity as defined.

The result of these calculated distinctions between the two defences is that ‘epileptics, sleepwalkers, those suffering from arteriosclerosis and diabetics during a hyperglycaemic episode, may all now be regarded as insane.’ This is surely an unacceptable position. After all, such people appear to fit far more comfortably within the (theoretical) realms of automatism than insanity. They are rational people, capable of recognising rule following situations, who are (largely) the victims of one off incidents of involuntariness. If we are to label a diabetic insane because they neglected to take their medication, are we to do the same with one who gets a migraine from omitting to take aspirin? The difference of cause is the resultant harm and the need for the courts to protect society.

Incidentally, close scrutiny of the M’Naghten rules leads us to conclude that where a defendant’s inability to recognise he was doing something wrong was due to something other than a defect of reason caused by a disease of the mind he would generally have no defence at all.

Things do not get any clearer when the defence of Diminished Responsibility is brought into the frame. The statutory provision for the defence is found in Section 2(1) of the Homicide Act 1957 and provides that a person shall not be convicted of murder:

“If he was suffering from such abnormality of mind (whether arising from a condition of arrested or retarded development of mind or any inherent causes or induced by disease or injury) as substantially impaired his mental responsibility for his acts or omissions in doing or being a party to the killing.”

The problems begin with semantics and normative questions of degree: what qualifies as ‘abnormality of mind,’ how much is ‘substantially’ and what is ‘mental responsibility’? Even debates on the questions have offered little assistance. For example, the Government, in an attempt to explain the key term, said that ‘abnormality of mind’ referred to conditions ‘bordering on insanity’ while excluding ‘the mere outburst of rage or jealousy’. Such an explanation is obviously of little worth considering that ‘the response of judges and psychiatrists?[to the section]? have ranged from the very generous to the very strict’. In fact the courts it seems, have entertained ‘practically any ground where it was thought morally inappropriate to convict the defendant of murder’. For example, psychopaths, reactive depressives , alcoholics and those in ‘disassociated states’ or suffering from ‘irresistible impulses’ have all been brought within the protective scope of the section.

Lord Parker in Byrne, also attempting to clarify the section’s ambit, said that it dealt with ‘partial insanity or being on the border line of insanity’. He went on to add that ‘Inability to exercise will-power to control physical acts? is? sufficient to entitle the accused to the benefit of this section; difficulty in controlling his acts? may be’. Confusions are evident here for, as Smith and Hogan note: ‘A man whose impulse is irresistible bears no moral responsibility for his act, for he has no choice; a man whose impulse is much more difficult to resist than that of an ordinary man bears a diminished degree of moral responsibility for his act’

It would appear then, that the former should be acquitted as insane rather than have his punishment mitigated. However, if the inability to control his acts is not caused by a ‘defect of reason’ or ‘disease of the mind’ then the defendant has no defence in insanity. In this respect therefore, the defence of diminished responsibility appears to be patching up the deficiencies of M’Naghten; acting as ‘a device for circumventing the embarrassments that flow from a mandatory sentence,’ or the stigma attached to a finding of insanity, by allowing judges to “follow in a common sense way their sense of fairness.”

Greiw, writing in 1988 comments on the section. He suggests that the section is not to be seen as a definitional aid rather it is ‘to be seen as legitimising an expression of the decision-maker’s personal sense of the proper boundaries between murder and manslaughter’. The result of the lax and open wording has allowed the defence of diminished responsibility to be used almost as a catch-all excuse, spanning, and adding to, the defences of insane and non-insane automatism. It has been able to accommodate states of mind and circumstance that would be insufficient for either automatism or insanity whilst at the same time justifying this accommodation by virtue of the increased severity of a murder charge.

To some this position is considered entirely unacceptable and contrary to the theories of blame and responsibility discussed hereto. Sparks for example, comments ‘to say that we are less willing to blame?a man if he does something wrong, surely does not mean: we are willing to blame him less, if he does something wrong.’ It would seem however, that due to the inadequacies of M’Naghten and the acceptance that some states of mind falling short of insanity should be considered mitigatory, the courts had little choice but to develop the defence of diminished responsibility in this way.

From the issues discussed in this essay it is clear that whilst, in theory, the three defences of Insanity, Automatism and Diminished Responsibility, do indeed exhibit differences, in practice they have become somewhat amalgamated. This is probably due to two factors:

First, it must be accepted that ‘there is no sharp dividing line between sanity and insanity, but that the two extremes? shade into one another by imperceptible gradations.’ This proposition leads us to conclude that first, the problem is one of definition. Second, the courts are aware that ‘pleading a blackout is one of the first refuges of a guilty conscience and is a popular excuse’. Therefore, they have tended to view the problem of involuntariness ‘with great circumspection and have adopted a restrictive approach as to when there should be a complete exemption from liability’. In order to balance this definitional problem with the requirement of certainty, whilst ensuring that only the deserving are completely acquitted, the law has had no alternative but to define distinct parameters. It is these parameters which have both caused the fudging of the two automatism defences and necessitated the creation of a diminished responsibility defence.

Whilst, in some respects, this amalgamation is unacceptable, its effect has been to provide blanket coverage for those defendants suffering from either a mental disorder, disassociated condition or episode of sudden involuntariness. Far from saying that the law has failed to ‘fully appreciate’ the differences it appears that the courts, due to restrictions, have simply created ad hoc a range of defences whose purpose is to reflect, on a continuum, impeachable notions of culpability.



1. Ashworth, Principles of Criminal Law (2nd ed., Oxford, 1995)

2. Clarkson. C.M.V. & Keating. H.M. Criminal Law. Text and Materials. (4th ed., 1998, Sweet & Maxwell)

3. Hart. H.L.A., Punishment and Responsibility, (1968, Oxford)

4. Smith , J.C. B. Hogan., Criminal Law (6th Edition, 1988, London, Butterworths.)

5. Williams. G., Textbook of Criminal Law (2nd ed., Stevens & Sons. 1983)


Dell, Diminished Responsibility Reconsidered. [1982] Crim.L.R. 809

Duff. R.A., Trial and Punishments J.L.S.S. 1986, 31(11), 433

Goldstein. A., The insanity Defense (1967)

Griew. E., The future of Diminished Responsibility. Crim. L.R. 1988, Feb, 75-87

Laurie. G.T., Automatism and Insanity in the Laws of England and Scotland. Jur. Rev. 1995, 3, 253-265

Mackay. I., The Sleepwalker is Not Insane. M.L.R. 1992, 55(5), 714-720

Padfield. N.,Exploring a quagmire: insanity and automatism. C.L.J. 1989, 48(3), 354-357

Royal Commission on Capital Punishment, Cmnd. 8932 (1949-1953)

Smith. J.C., Case and Comment. R. v. Hennessy. (1989) 86(9) L.S.G. 41; (1989) 133 S.J. 263 (CA)

Smith. K.J.M. & Wilson. W., Impaired Voluntariness and Criminal Responsibility: Reworking Hart’s Theory of Excuses ? The English Judicial Response. O.J.L.S. 1993, 13(1), 69-98

Sparks. Diminished Responsibility in theory and Practice (1964) 27 M.L.R 9

Virgo. G., Sanitising Insanity ? Sleepwalking and Statutory Reform C.L.J. 1991, 50(3), 386-388


1. Alphacell [1972] 2 All ER 475

2. Burgess [1991] 2 W.L.R. 106 C.O.A. (Criminal Division)

3. Byrne [1960] 3 All ER 1

4. Cooper v. McKenna [1960] Q.L.R 406

5. Hennessy (1989) 89 Cr.App.R 10, CA

6. Kemp [1956] 3 All ER 249; [1957] 1 Q.B.399

7. M’Naghten’s Case (1843) 10 C & F, 200, 8 Eng. Rep. 718.

8. Quick and Paddison [1973] Q.B. 910

9. Seers [1985] Crim.L.R, 315

10. Sullivan [1984] A.C. 156 (House of Lords)

11. Tandy [1988] Crim.L.R 308

12. Tolson (1889)


1. Homicide Act. 1957.

2. Trial of Lunatics Act 1883

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