This work sets out to show that all attempts at reformulating insanity have been surrounded by controversy. This is because of the insanity defence's foundation on a rigid distinction between responsibility (sanity) and irresponsibility (insanity) - a distinction at odds with psychiatric theory. The author examines the diminished responsibility defence and its success in abating the medico-legal controversy surrounding the insanity defence. This is achieved by adopting a multi-jurisdictional approach (American, Irish and English developments are examined) and by exploring legal, medical and socio-legal historical writings on this subject.