Insanity and the Capacity for Criminal Responsibility

There are two different ways in which the insanity defence could he constructed. These relate to different ways in which the insanity defence might question the responsibility of the accused. Either the defence might show that the act in question was not performed in the appropriate way (that the accused lacks attribution-responsibility) or it might show that the agent was not an appropriate subject for criminal responsibility (that he or she lacks capacity-responsibility). Sometimes it is thought that these possibilities collapse into each other: it is only those that cannot perform their acts in the appropriate way that lack the capacity to be criminally responsible. This essay shows three things: first, that Scots criminal law, at least since the nineteenth century, is in a state of confusion between a capacity-responsibility conception of the defence and an attribution-responsibility conception. Second, that capacity-responsibility does not collapse into attribution-responsibility: there are some agents who are capable of forming mens rea but who ought not to be made criminally responsible due to their mental disorder. Third, that a sophisticated account of the capacity-responsibility conception can provide a version of the insanity defence that is both theoretically more elegant and practically more advantageous than the attribution-responsibility conception that has found favour in England and in some Scots decisions.