Abstract. In 1948,Canadian parliamentarians unanimously voted in favour of adopting criminal sexual psychopath legislation. An American invention that combined the force of the law with the curative abilities of psychiatry, sexual psychopath laws were the product of faith in science, and especially ";mental health,"; to solve social problems, combined with growing public anxiety about violent sexual assault, particularly against children. This mid-century medico-legal experiment has been well documented by American historians.