diminished capacity

n.

Lack of ability to comprehend the nature of a crime one has committed or to restrain oneself from committing a crime.

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This entry contains information applicable to United States law only.

This doctrine recognizes that although, at the time the offense was committed, an accused was not suffering from a mental disease or defect sufficient to exonerate him or her from all criminal responsibility, the accused's mental capacity may have been diminished by intoxication, trauma, or mental disease so that he or she did not possess the specific mental state or intent essential to the particular offense charged.

1. The McNaghten Rules
2. Doe–Ray tests of insanity
3. Diminished responsibility in Scotland
4. Diminished responsibility in England
5. Proposals for reform

1. The McNaghten Rules

In English law until 1957 there was only one defence based on disease of the mind available to a defendant, that of insanity. In 1843 an authoritative pronouncement by all the judges answered questions put to them by the House of Lords in its legislative capacity. McNaghten had been tried for the murder of Sir Robert Peel's private secretary, Edward Drummond, under the mistaken impression that he was shooting at Sir Robert himself. He was acquitted by the jury on the ground of insanity. The acquittal aroused widespread controversy, and was debated in the House of Lords, with the result that their lordships put abstract questions to the judges. The judges gave their answer to the second question in the following terms:

• To establish a defence on the grounds 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. (F (1843) 10 Cl. & F. 200)

From the medical standpoint, this all-or-nothing approach to psychological functioning was already obsolete. It had also been shown that inability to distinguish between right and wrong was only one symptom of insanity, and that many mentally disturbed persons knew the difference between right and wrong. In 1838 Isaac Ray had published in the USA his work A Treatise on Medical Jurisprudence of Insanity, described in 1961 by a psychiatrist as the best book in the English language on forensic psychiatry (Diamond (1961) 14 Stan. LR 59). Defence counsel had used this book at the trial of McNaghten, but to no effect.

2. Doe–Ray tests of insanity

In the United States the McNaghten Rules were adopted as the test of insanity in most states, but the state of New Hampshire was an exception. Judge Charles Doe, later chief justice of that state, began to correspond with Isaac Ray, an exchange of letters that continued from 1866 to 1872. One passage from Ray's work may be cited: 'Insanity is a disease, and, as is the case with all other diseases, the fact of its existence is never established by a single diagnostic symptom, but by the whole body of symptoms, no particular one of which is present in every case.'

Convinced of the inadequacy of the McNaghten tests, Doe came to regard the question of insanity as one of fact to be left to the jury, and by 1869 had converted his brother judges in the state to that view (State v. Pike 49 NH 399). In a letter to Ray he wrote: 'Giving this matter to the jury leaves the way open for the reception of all progress in your science. One jury is not bound by the verdict of another.' Doe and Ray are thus left in harmonious juxtaposition.

3. Diminished responsibility in Scotland

The McNaghten Rules had never been accepted unreservedly in Scotland, and in the very decade in which Charles Doe had wrought a transformation in New Hampshire, Lord Deas initiated a new defence, proof of which led not to an acquittal, but to a verdict of culpable homicide instead of murder. This was in HMA v. Dingwall 1867 5 Irv. 466. The development did not arise from close contact with medical writing, and seemed out of character for the judge himself, for his general attitude tended towards rigidity and severity. It has even been suggested that his direction to the jury may have sprung from a respect for Hogmanay, as the defendant's fatal attack on his wife had followed bouts of excessive drinking at that season, a time apparently when many a reasonable Scot will consume inordinate quantities of whisky. Whatever the reasons for the new idea, Lord Deas persisted in it. Before his retirement in 1885, he had contributed six of the first nine reported cases embodying the new doctrine. In the third case he instructed the jury that a weak or diseased mind, not amounting to insanity, might competently form an element to be considered in the question between murder and culpable homicide (HMA v. Granger 1878 4 Coup. 86). In the last of the six, he said that Dingwall was now the recognized law of the land (HMA v. Gove 1882 4 Coup. 598). The new defence received the name of diminished responsibility in HMA v. Edmonstone 1909 2 SLT 223. In HMA v. Savage 1923 JC 49 a direction to the jury from Lord Justice-Clerk (Alness) has come to be regarded as a locus classicus. He stressed that the doctrine must be applied with care, and that there must be aberration or weakness of the mind, some form of mental unsoundness, a state of mind bordering on insanity, rendering the defendant only partially responsible.

It has been argued by some distinguished writers on the law of Scotland that diminished responsibility operates merely in mitigation of sentence, and does not affect responsibility. Such a view is certainly not tenable in England, where Parliament created the defence in 1957.

4. Diminished responsibility in England

In England the Royal Commission on Capital Punishment, 1949–53, heard much evidence on the operation of the defence of diminished responsibility in Scotland, but made no recommendation for its adoption, regarding the matter as outside its terms of reference. In 1956, however, during a debate in the House of Commons on capital punishment, the Home Secretary undertook to consider the question further. This led to section 2 (1) of the Homicide Act 1957, whereby:

• Where a person kills or is a party to the killing of another, he 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 and omissions in doing or being a party to the killing

. The defence is called diminished responsibility in a marginal note to the section. The burden of proof is placed on the defence, as in Scotland and under the McNaghten Rules. In such cases, as in all instances where a legal burden of proof is placed on the defence, the defendant has to establish the defence on a balance of probability, or in more homely language that it is more likely than not that his responsibility is diminished. If so proved, murder is reduced to manslaughter, just as in Scotland it is reduced to culpable homicide. It applies only to murder, following the predominant Scottish view. A successful defence of insanity leads to a verdict of 'not guilty by reason of insanity'.

The introduction of this new defence, coupled with the abolition of capital punishment for murder by Parliament in 1965, has led to the virtual disappearance of the defence of insanity.

From the outset difficulties were found in directing the jury on the question of fact they had to determine under section 2 (1). In R. v. Spriggs 1958 1 QB 270, the trial judge read the section to the jury, reviewed in detail the evidence relevant to the defence, made no attempt to explain the various medical terms that had figured in the evidence, and gave the jury copies of the section as they retired. The Court of Criminal Appeal quoted the charge to the jury from a Scottish case, which consisted largely of a quotation from the charge to the jury in Savage mentioned above as a locus classicus. The court considered that the case had been put to the jury in the only way it could be put, and affirmed the conviction.

In R. v. Walden 1959 43 Cr. App. R. 201, the trial judge construed the section as meaning: 'Poor fellow, he is not insane, but not far from it; his mental condition is one which is bordering on, but not amounting to insanity.' He gave the jury copies of the section. The Court of Criminal Appeal refused leave to appeal. Parliament had not defined 'abnormality of mind' or 'mental responsibility'. The reference to substantial impairment connoted a question of degree, and questions of degree are questions of fact in each case.

At this stage English juries were not receiving the necessary guidance: Charles Doe, while insisting that the question of mental disease was one of fact for the jury, had also stressed that the jury must be given some help. Help was forthcoming from the Court of Criminal Appeal in R. v. Byrne 1960 2 QB 396. The court gave a definition of two important concepts in the section. 'Abnormality of mind' meant a state of mind so different from that of ordinary human beings that the reasonable man would term it abnormal. It covered the mind's activities in all its aspects — not only the perception of physical acts and matters and the ability to form a rational judgement whether an act is right or wrong, but also the ability to exercise will power to control physical acts. 'Mental responsibility' pointed to a consideration of the extent to which the accused's mind is answerable for his physical acts; this must include a consideration of the extent of his ability to exercise will power to control his physical acts. Inability to exercise will power to control such acts entitles the accused to the benefit of the section; difficulty in controlling such acts may do so, if great enough to amount to substantial impairment. The jury must decide, though there is no scientific certainty to guide them. Thus the court in Byrne clearly decided that an irresistible impulse falls within the concept of diminished responsibility, a status it never achieved under the McNaghten Rules.

The effect of Byrne was soon apparent. In Rose v. Reginam 1961 45 Cr. App. R. 102, a summing-up that had passed muster in Walden now led to a successful appeal. In R. v. Terry 1961 2 QB 314, a summing-up that failed to explain section 2 (1) on the lines laid down in Byrne was held deficient. Further, the jury had been handed a transcript of volumes of medical evidence without explanation. It is of course the duty of the trial judge to take the jury through the evidence, trying to synthesize it and render it easier to digest. The conviction was in fact upheld as the crucial question was held to be whether the accused was shamming, and on this matter the summing-up was adequate. In R. v. Gomez 1964 48 Cr. App. R. 310, a summing-up to the jury by Judge Paull on similar lines to that in Walden was again held inadequate: the proper course was to tell the jury what in law the section means, and what are the ingredients in the section, and then direct them on the evidence. The conviction was reduced to manslaughter. In Walton v. R. 1978 AC 788, the Privy Council put the clock back to Walden by indicating that the main question before the jury was whether the state of mind of the defendant was bordering on but not amounting to insanity, supporting this view by a quotation from Byrne itself. It is submitted that this is oversimplified, and regard should be had to the more thorough examination of the question demanded by Byrne rather than to an isolated passage taken out of context.

Although the question is one that the jury must decide, if they ignore unchallenged medical evidence that all points to substantial impairment, an appellate court may reduce the conviction to manslaughter, on the ground that the verdict of murder is unsafe or unsatisfactory, as in R. v. Matheson 1958 42 Cr. App. R. 145. The verdict may, however, be allowed to stand if the medical evidence was challenged in cross-examination, as in R. v. Latham 1965 Cr. LR 434, or the solitary expert witness in the case, who considers the impairment to have been substantial, is unsupported by objective evidence of any history of mental disorder, as in Walton (above).

An issue of considerable importance is the position of one diagnosed as psychopathic personality as defined by the Mental Health Act 1959. In the case of Fenton (1975, 61 Cr. App. R. 261) it was concluded that psychopathic personality was no defence under the terms of the Homicide Act 1957, regardless of whether the accused was affected by alcohol at the time of his offence. Furthermore, as intoxication with drink or drugs cannot be regarded as an 'inherent cause' of mental abnormality, an attempt to reduce the verdict to manslaughter in place of murder on the ground that the accused was drunk at the time of the killing will not succeed.

Nevertheless, the introduction of the defence of diminished responsibility has undoubtedly had beneficial effects. This is because psychiatrists have adapted themselves to giving opinions in accordance with the legal formula, vague and unscientific as it undoubtedly is.

5. Proposals for reform

The Butler Committee on Mentally Abnormal Offenders, in their report of 1975, Cmnd. 6244, recognizing the difficulties under which experts were labouring, proposed an alteration in the wording of section 2 (1), substituting after the word 'murder', 'if there is medical or other evidence that he was suffering from a form of mental disorder as defined in section 4 of the Mental Health Act 1959, and if, in the opinion of the jury, the mental disorder was such as to be an extenuating circumstance which ought to reduce the offence to manslaughter'. The Committee claims that this amendment would provide a firm base for testifying psychiatrists to diagnose mental state. The claim is justified. The Mental Health Act 1959 contains definitions of mental disorder, psychopathic disorder, subnormality, and severe subnormality, so that the expert is now operating in a familiar field; and the Mental Health Act 1983 does not materially alter this situation. Although mental disorder includes psychopathic disorder as one of the defined components, as already mentioned, it is unlikely that this diagnosis will be admissible as a defence of diminished responsibility under the Homicide Act 1957.

The Criminal Law Revision Committee in its Fourteenth Report of 1980 (Cmnd. 7844) recommends that the Butler wording should be changed so that instead of the need for the jury to seek 'an extenuating circumstance' their quest should be for 'a substantial enough reason'.

The Fourteenth Report recommends, as the Committee had recommended in its Eleventh Report of 1972, and the Butler Committee in 1975, that there should be no burden of proof on a defendant raising a plea of insanity or diminished responsibility: the burden of proof should be on the prosecution to disprove the defence beyond reasonable doubt.

See also criminology.

— R. N. Gooderson

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