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Insanity: Evaluation & Reform

Model Answer | A Level

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Evaluate the defence of insanity, including suggestions for reform

The defence of insanity has been criticised for many years and need for reform seems generally accepted. Dr Winstanley famously spoke about the longstanding wide criticism of the M'Naghten rules in a House of Commons debate in 1967. He said .. it is interesting to note that as long ago as 1874 the noble Lord, Lord Bramwell.. said that ‘the present law lays down such a definition of madness that nobody is hardly ever really mad enough to be within it’....

On numerous occasions, studies have looked at the defence of insanity but substantial reforms have yet to be enacted. Law Commission have recently begun their Tenth Programme of Reform one area under consideration is Unfitness to plead and the insanity defence. The document outlining the programme discussed the intention to look at the defence of insanity and stated .. the problems with the current law are many and deep....


Definition of insanity is a legal not medical one which raises uncertainty.

Defendants who may know what they are doing is wrong but have an irresistible urge to act in that way, (psychopaths (Byrne (1960))). Conversely those suffering some physical illnesses may be considered legally insane (diabetes (Hennessey (1989))).

Burden of proof

The burden of proof shifts depending on whether prosecution or defence is arguing insanity. This is confusing, inconsistent and provides an added complication for a jury.


Implications of a verdict of not guilty by reason of insanity are significant.

A finding of insanity can lead to indefinite detention in a secure hospital which can be a lengthier sentence than life sentence, with a tariff of 15 yrs. It is well documented many offenders suffer mental health problems, yet insanity relatively uncommon defence.

Under Article 5 of the European Convention on Human Rights a person of unsound mind may be detained but are also afforded protections. These protections interpreted to mean need for objective medical expertise which is not always involved in an insanity plea.

There is huge social stigma surrounding the term insanity. The Law Commission have expressed concern that .. a finding of insanity attracts huge stigma and it is a finding which, under the current law, may be made in cases where the defendant was not mentally disordered....

The Butler Committee 1975 report on Mentally Abnormal Offenders recommended the introduction of a new verdict of not guilty by reason of mental disorder. This could be applied where a defendant was unable to form the required mens rea due to mental disorder or was aware of his actions but was at the time suffering from a severe mental illness. It was suggested this defence may help alleviate stigma of insanity.


It has been recommended that proof of a severe mental disorder should be sufficient to negate responsibility. However, this would allow criminal responsibility to be determined by the presence of a mental problem rather than establishing a standard of criminal responsibility. Such arguments lead to the question as to whether the defence of insanity should be available for all crimes, even those not requiring mens rea.

The Royal Commission on Capital Punishment 1953 found the M’Naghten Rules inadequate, criticising the scope of the rules. They recommended that mental deficiency be considered a factor.


The overlap between automatism and insanity defences is clear. The distinction lies in whether the defendant’s conduct is due to an automatic state induced by an internal or external factor. However, the defences lead to very different verdicts. A defendant who successfully arguing automatism is entitled to acquittal compared to a verdict of not guilty by reason of insanity which means the judge must impose some order.

The Law Commission have noted that .. the relationship is unsatisfactory because of the ‘external factor’ doctrine... .

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