M’Naghten’s Case

Case Name: M’Naghten’s Case
Citation: 8 Eng. Rep. 718 (1843)

Facts: M’Naghten was indicted for the murder of the secretary to the prime minister when he sought to assassinate the prime minister. M’Naghten had many prominent medical experts that provided testimony that he suffered from acute insanity. The jury returned a verdict of “not guilty, on the ground of insanity.”

The discussion surrounds questions that were asked by the House of Lords to the English judiciary about when a jury would be charged with determining the defense of insanity. The House of Lords wanted to have a better policy on when the defense of insanity could be used.

Legal Answer: The House of Lords determined that “every man is to be presumed to be sane” until the “contrary be proved to their satisfaction.” The House required that to establish a defense on the ground of insanity, it must be clearly proved that, at the time of the committing of the act, the party accused was laboring under such a defect of reason, from disease of the mind, as not to know the nature and quality of the act he was doing; or if he did know it, that he did not know he was doing what was wrong – this should not be a question of “actual knowledge of the law of the land” but the presumption that everyone must be taken conclusively to know it, without proof that he does know it.

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