In 1843, Daniel McNaughton opened probably the biggest can of worms that exists in law when he shot and killed Edward Drummond, Private Secretary to the then British Prime Minister Sir Robert Peel. The murder was a mistake; McNaughton meant to kill Peel. His defence was based largely around the fact that for years he had suffered from paranoid delusions, namely that Peel's Conservative Party was trying to kill him. McNaughton was found not guilty by reason of insanity, and was committed to Bethlem Hospital, and thence to Broadmoor Criminal Asylum shortly after it opened. The case gave cause to great debate in the House of Lords, resulting in the McNaughton Rules, which, although having no statutory basis, were afforded the same status as actual law.

In summary, these rules state that a person cannot be held responsible for a crime if they were 'labouring under such a deficit of reason from disease of the mind to not know the nature and quality of the act; or that if he did know it, that he did not know that what he was doing was wrong'.

Development

It is clear that this presents far too narrow a definition of insanity to be workable, and in section 2 of the 1957 Homicide Act the plea of 'Diminished Responsibility' is introduced to widen the catchment area of 'insanity' to include diseases of the mind and actual physical damage to the brain. Regina¹ v Kemp, 1957, shows us that a man suffering from a case of arteriosclerosis (an umbrella term relating to disorders of the blood supply) which induced automatism killed his wife during a blackout and was cleared when the judge ruled that physical damage of the brain could amount to disease of the mind. This new view was echoed by Lord Denning in 1963:

It seems to me that any mental disorder that manifests itself in violence and is prone to recur is a disease of the mind. At any rate it is a disease for which a person should be detained in hospital rather than given an unqualified acquittal.

In the USA, the Durham rule was used. It states that '...an accused is not criminally responsible if his unlawful act was the product of mental disease or defect'. This was put forward in 1954, but has since been replaced by the Brawner Decision, which expounds the point further:

A person is not responsible for criminal conduct if, at the time of such conduct, as a result of mental disease or mental defect he lacks substantial capacity to either appreciate the wrongfulness of his conduct or to conform his conduct to the requirements of the law.

In Regina v Byrne, 1960, the Court of Criminal Appeal indicated that they were satisfied with the scope of the premise 'abnormality of the mind' and also mentioned 'the ability to exercise willpower to control physical acts in accordance with rational judgement'. In saying this, the concept of Irresistible Impulse is recognised, after being excluded under the scope of the McNaughton Rules. This was first mentioned in the USA in 1922 and it defines that 'a person cannot be held responsible for a criminal act if it can be shown that they acted through an irresistible impulse which they were unable to control because of a mental disorder' (Arthur S Reber, 1985). Most US courts have rejected this and it is rarely used today.

Following the abolition of the death penalty in the UK, the plea of insanity has rarely been used, the preferred plea being diminished responsibility. If this defence, or that of automatism is used, the prosecution is allowed to rebut with evidence of insanity (Regina v Kemp).

Law and Psychology

As far as any legal definition could ever be, the concepts of insanity and diminished responsibility seem quite clear and well defined. But if we look to the field of psychology, we see that these terms just do not exist. The studies of Rosenhan are particularly relevant, being both a professor of Law and Psychology. He was the first to note that sane and insane are legal terms and not psychiatric, and that no psychiatrist will ever make a diagnosis of sanity or insanity. A two-part study by Rosenhan carried out in 1973 demonstrated how difficult it was for a member of the medical profession to make an accurate diagnosis of mental disorder.

Eight psychiatrically 'normal' people presented themselves to eight different mental hospitals in the USA, complaining of hearing voices saying 'empty', 'hollow', and 'thud'. Apart from their names and addresses, these symptoms were the only falsehoods involved. All were admitted, and after admission claimed that the voices had stopped. All were eventually discharged with a diagnosis of schizophrenia in remission.

For the second part, these findings were presented to the staff of another hospital, and told that the same experiment would be carried out on them. Each member of staff was asked to rate each new admission, as to whether they rated the patient genuine or fake. Out of the 193 new admissions over three months, 41 were alleged to be fake by at least one staff member; 23 were suspected by one psychiatrist and a further 19 by one psychiatrist and one other member of staff. All were genuine patients.

The term 'insane' is itself inaccurate and open to wide and varied interpretation. Typically, the image of an insane person is that of one whose grip on reality is chronically loosened or severed; incapable of coherent thought or speech; unable to make logical, rational decisions; the old-fashioned image of the 'village idiot' is the prevalent one. No jury would have trouble finding a plea of insanity unreasonable when faced with someone who looked like that. But consider these three different types:

1. One who is of above average intelligence, who is charming and socially skilled; disarming, amoral, manipulative, insensitive to the feelings of others, unable to tolerate frustration, callous, unable to settle or make commitment.

2. One who is jumpy, irritable, finds it difficult to concentrate or make decisions; has trouble sleeping, has a poor appetite, and suffers from vague feelings of panic or nausea that leaves them exhausted.

3. One who has decreased sexual desire, loss of appetite, a slowing of the mental processes, a general feeling of hopelessness and despair, worthlessness and unattractiveness, delusions of physical decay and an expectation of punishment.

The first is a typical sociopath or borderline psychopath, the second suffers from an anxiety neurosis, and the third a depressive disorder. None of these, put before a jury, would conform to the 'insane' image portrayed earlier. Yet all these three types are categorised as mental disorders by the two leading psychiatric diagnostic manuals, DSM-III-R (Diagnostic & Statistical Manual of Mental Disorders (Third Revision (1987))) and ICD10 (International Classification of Diseases).

At his trial, Peter Sutcliffe, the notorious 'Yorkshire Ripper' told of the voice he was hearing that explained to him that he was the instrument of God's will. He was instructed to kill prostitutes by the voice, which he described as benign and reassuring. He was found guilty of the murders of 13 women, and the attempted murders of seven more. Schizophrenia is rated probably the most serious mental disorder, and for a diagnosis of schizophrenia a patient must exhibit one of the seven 'first rank' symptoms and have no physical brain damage (Schneider, 1957). Sutcliffe openly exhibited four out of the seven. He was considered sane enough to stand trial for his crimes, for which he received 20 concurrent life sentences. He served a token period in prison but, like his famous predecessor Daniel McNaughton, was soon moved to Broadmoor Special Hospital. On reflection, it would appear that Sutcliffe was sane enough to stand trial for his crimes, but not sane enough to serve the punishment for them.