Common questions

No. Mental illness is not in itself a defence. Insanity, automatism and diminished responsibility each ask a specific question about how a condition affected the defendant at the time of the offence, and many defendants with serious mental illness meet none of them. Mental illness may still be highly relevant to sentence.

Insanity is a complete defence to any offence, decided under the M'Naghten Rules: did a disease of the mind mean the defendant did not know the nature and quality of the act, or that it was wrong? Diminished responsibility is a partial defence to murder only. It asks whether an abnormality of mental functioning from a recognised medical condition substantially impaired the defendant's understanding, judgment or self-control, and explains the killing. If it succeeds, the conviction is for manslaughter.

No. Section 2 of the Homicide Act 1957 applies only to a charge of murder. A defendant charged with attempted murder may rely on insanity, or the psychiatric evidence may bear on intent or on sentence.

Not where the intoxication was voluntary. A state brought on by voluntarily taking alcohol or drugs cannot found insanity or automatism. Intoxication may still be relevant to whether the defendant formed the intent the offence requires.

Yes. Acute intoxication is not a recognised medical condition, but alcohol dependence syndrome is, and it can found the defence if the other elements of the statutory test are met. Where a defendant had an abnormality of mental functioning and was also intoxicated, the question is whether the abnormality substantially impaired their abilities and explains the killing notwithstanding the intoxication.

It can. Personality disorders are recognised medical conditions, so the question is whether the disorder caused an abnormality of mental functioning that substantially impaired the defendant's understanding, judgment or self-control, and provides an explanation for the killing.

The defendant is acquitted, but in the Crown Court the court must then make one of three orders under section 5 of the Criminal Procedure (Insanity) Act 1964: a hospital order (with or without a restriction order), a supervision order, or an absolute discharge. Where the charge is murder and the conditions for a hospital order are met, the order must be made with restrictions.

A jury may not return a verdict of not guilty by reason of insanity except on the written or oral evidence of two or more registered medical practitioners, at least one of whom is approved under section 12 of the Mental Health Act 1983.

The jury. The psychiatric evidence informs the decision, and in practice is essential, but whether the legal test is met is a question for the court. The expert's duty is to the court, and the report should explain the reasoning so that the jury can weigh it.

It can be, but since R v Burgess [1991] 2 QB 92 sleepwalking has been treated as insane automatism, because its cause is internal. A successful defence therefore leads to the special verdict of not guilty by reason of insanity rather than an outright acquittal.

Because the law divides automatism by its cause. Hypoglycaemia brought on by insulin has an external cause, and can lead to an outright acquittal. Hyperglycaemia from untreated diabetes has an internal cause, and is treated as insanity. The distinction is widely criticised, but it is the law.

Yes. Fitness to plead concerns the defendant's condition at the time of trial; insanity concerns their mental state at the time of the offence. A defendant who was acutely unwell at the time may have recovered by the trial, and the reverse is also possible. The two questions are assessed separately.

An account of the sources relied on, the defendant's history, the diagnosis and the evidence for the defendant's mental state at the time of the offence, followed by a reasoned opinion on each element of the relevant legal test. It should address the role of any intoxication, consider alternative issues such as intent or fitness to plead, and, where a defence may succeed, the appropriate disposal.