Introduction

Abstract The introductory chapter explores a number of themes which emphasize the highly differential character of the insanity defence across many jurisdictions. It confronts the fact that little is known about how the defence operates in different jurisdictions. The chapter explores various theories governing the origins and purposes of the defence. It notes that lack of rationality is the core of many expressions of the defence, often to the exclusion of volitional or emotional elements. The chapter investigates the claim, amongst others, that the defence should concern itself with an inquiry into a person’s character rather than capacity for choice, but ultimately recognizes that the former is unduly problematical. In exploring the theoretical basis for the insanity defence, the chapter notes the diversity of standards and rationales for assessing criminal capacity. The debate around the abolition of the defence is discussed, together with an extended discussion on the enduring claims for a rationality basis for the defence. This includes whether the rationality standard is capable of accommodating a volitional limb. The chapter concludes with a discussion of the defence’s ‘problematical’ nature in light of the enduring challenges it presents for lawyers, psychiatrists, legislators, and the general public alike.