ABSTRACT
The defence of irresistible impulse will mean little or nothing to today’s jurist. However, for over a century it was urged by members of the medical and legal professions, both in England and Ireland, either as a replacement for or a supplement to the right-wrong test embodied in the McNaghten Rules. Although the identification of moral insanity may be attributed to Prichard, it appears that Etienne Georget, a disciple of the French psychiatrist Esquirol, was responsible for the “discovery” of volitional insanity. Smith has uncovered some unreported cases in the medical literature of the day, where medical evidence of an irresistible impulse led to a successful defence of insanity. The wording of the motion seems to suggest that some insane persons should be excused because their delusions led to uncontrollable impulses. The most relentless judicial advocate of irresistible impulse was to be Sir James Fitzjames Stephen.
