Abstract
The criminal law's unified conception of the person will usually preclude the argument that a diagnosis of multiple personality disorder may ground a successful insanity defence. In effect, when carrying out specific acts in a particular frame of mind the actor is deemed to act as the agent of the whole legal person, who is therefore criminally responsible for that conduct. Alternative arguments, which would divide up the person for the purposes of attributing criminal responsibility, are not supported by legal principle or theory. They are occasionally raised by defendants, however, as in recent cases in the United States and New Zealand. This article examines one such heretical argument as an illustration of the confusion of psychological and legal kinds. An analogy is then drawn between the more orthodox approach and theories of agency used widely in the law.