Macnaughton's Case, Rules In

Macnaughton's Case, Rules in [4 St. Tr. (N.S.) 847]. A discussion took place in the House of Lords upon the direction to the jury by Tindal, C.J., in the trial of Macnaughton, and as a result a series of questions were put to the judges. The answers of the majority constitute 'the rules in Macnaughton's case,' and have been accepted as laying down the law as to insanity with reference to criminal responsibility. See Archbold, Crim. Pleading, etc., 25th Edn., p. 15 et seq. The rules have been the subject of much discussion and criticism by political, medical, and legal writers (see, for example, Lord Birkenhead's letter to The Times, May 26th, 1924). The main rule which is laid down is, that in order to establish a defence on the ground of insanity, it must be proved that, at the time of the committing of the act, the person accused was labouring 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 that he was doing what was wrong. The onus of proving insanity lies on the defence.