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Criminal | Defences

Insanity: Evaluation & Reform

Revision Note | A Level

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  • defence of insanity has been criticised for many years and need for reform seems generally accepted
  • Dr Winstanley, set out objections in House of Commons debate in 1967:
  • .. These rules were formulated following the case of Daniel M'Naghten and they are still in force despite the fact that they have been almost constantly subjected to criticism and attack, not only by the medical profession but by lawyers and members of the general public...
  • .. 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’...


  • definition is a legal not medical one, which raises uncertainty
  • means some people suffering from certain mental disorders are excluded
  • for example Ds 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

  • burden of proof shifts depending on whether prosecution or defence is arguing insanity
  • confusing and inconsistent, provides an added complication for a jury
  • conflicts with the principle the burden lies with the prosecution

    Woolmington v DPP (1935)

    • Viscount Sankey: .. No matter what the charge or where the trial, the principle that the prosecution must prove the guilt of the prisoner is part of the common law of England and no attempt to whittle it down can be entertained...


  • implications of verdict makes insanity a less favoured defence
  • finding of insanity can lead to indefinite detention in a secure hospital
  • can be a lengthier sentence than life sentence, with a tariff of 15 yrs
  • well documented many offenders suffer mental health problems, yet insanity relatively uncommon defence
  • under Article 5 of European Convention on Human Rights a person of unsound mind may be detained but are also afforded protections
  • protections interpreted to mean need for objective medical expertise, not always involved in an insanity plea
  • social stigma surrounds the term insanity
  • argued it is an outdated term, should not be applied to those suffering from mental illnesses
  • in cases involving people suffering from diabetes or epilepsy it seems wholly inappropriate


  • been recommended that proof of a severe mental disorder should be sufficient to negate responsibility
  • but would allow criminal responsibility to be determined by the presence of a mental problem rather than establishing a standard of criminal responsibility
  • question as to whether the defence should be available for all crimes, even those not requiring mens rea


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

Proposals for reform

  • on numerous occasions, studies have looked at the defence of insanity
  • substantial reforms have yet to be enacted
  • Law Commission have begun a review of this area of the law which may eventually lead to considerable reform

Royal Commission on Capital Punishment 1953

  • found the M’Naghten Rules inadequate
  • criticised the test for responsibility and scope of the rules
  • recommended that mental deficiency be considered a factor
  • suggestions were not implemented
  • although partial defence of diminished responsibility addressed some of the criticisms

Butler Committee 1975

  • report on Mentally Abnormal Offenders stated major reform necessary
  • main recommendation was introduction of a new verdict of not guilty by reason of mental disorder
  • could be applied where D 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
  • suggested this defence may help alleviate stigma of insanity

Law Commission

  • under Commission’s Tenth Programme of Reform, commenced in 2011, one area under consideration is Unfitness to plead and the insanity defence
  • document outlining the programme for reform discussed intention to look at the defence of insanity:
  • .. expect that the rules governing the criminal liability of the mentally ill would be informed by humane principles while recognising the Government’s legitimate concern that the public should be adequately protected from harm...
  • .. The link between crime, mental illness and intoxicants can be seen in our prisons where many inmates have a history of abuse of intoxicants combined with mental health problems...
  • .. The problems with the current law are many and deep...
  • .. As well as the test for determining fitness to plead being antiquated, there are unanswered questions as to the scope of the trial of the facts following a finding of unfitness to plead...
  • ..There are other fundamental issues that need to be addressed. One is the relationship between insanity and automatism. The relationship is unsatisfactory because of the ‘external factor’ doctrine...
  • .. The relationship between insanity and the partial defence of diminished responsibility is also complex and needs to be re-evaluated...
  • .. The area is highly suitable for a Law Commission project. The foundations of the current law rest on judicial rulings made in the first half of the nineteenth century. As a result, the legal tests consist of concepts on which there is no agreed psychiatric meaning. 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...
  • consultation process is currently underway and recommendations from the Law Commission will provide suggestions for future reform
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