M’Naghten Rules

M’Naghten Rules2016-12-16T04:08:36+00:00

M’Naghten Rules

M'Naghten Rules image from New Medical Terms

M’Naghten Rules


A series of legal tests that many courts in the English speaking world as well as in the United States use to define mental incompetence (“insanity”).

Under the 1843 ruling by the House of Lords, to establish a legal defence of insanity in English common law jurisdictions, it must be clearly proven 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 acts, or, if he did know it, that he did not know that what he was doing was wrong.”

The M’Naghten Rules were the first real attempt to modify the tenets of criminal law when it faces mentally incompetent defendants. The Rules arose from M’Naghten’s Case (1843 10 C & F 200), in which The House of Lords asked a panel of judges to provide guidance for juries considering a defendant’s plea of insanity. Daniel M’Naghten had tried to assassinate British Prime Minister, Robert Peel, but actually shot Peel’s secretary, Edward Drummond, who died five days later. The Rules have become a standard test for criminal liability in relation to mentally disordered defendants in common law jurisdictions. When the tests set out by the Rules are satisfied, the accused may be adjudged “not guilty by reason of insanity” and the sentence may be a mandatory or discretionary (but usually indeterminate) period of treatment in a secure hospital facility, or otherwise at the discretion of the court instead of a punitive disposal. The insanity defence is recognised in Australia, Canada, England and Wales, Hong Kong, New Zealand, the Republic of Ireland, and most U.S. States…but rarely works when evoked as a legal argument, unless the defendant is barking mad

Reference en.wikipedia.org/wiki/ M’Naghten_Rules

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