What, if any, is the distinction between offences and exculpatory defences, between definitional elements and defence elements, between rules and exceptions? In recent years the courts have shown a tendency to attach legal importance to this distinction, even as a matter of substantive law. But ought it to have this importance, and anyway is it usable?

On their face, exculpatory defences often relate to the same kind of question as the inculpation provisions of the criminal law. The offence-creating provision states what must or must not, in general, be done; the exculpatory provision states the limits of the prohibition in particular circumstances. As Professor Paul Robinson expresses it, in a long and learned article on defences, defences ‘refine the wording of the offence’; they ‘provide a more sophisticated account, when needed, of the harm or evil sought to be prohibited’. But the refinements may be expressed in the provision itself, as well as in the defences.