Strictly speaking, the M'Naghten rules apply to a person who is suffering from insanity which manifests itself in insane delusions. Nevertheless, the rules were accepted as the general test for insanity in Irish law, despite the fact that doubts had been expressed as to whether they represented a comprehensive statement of Irish law on the issue. However, following the decision of the Supreme Court in the People v. Hayes in 1965, and its subsequent approval by the Supreme Court in Doyle v. Wicklow County Council in 1974, it is clear that the M'Naghten rules are not the sole and exclusive test for the defence of insanity in Ireland. The decision in the latter case means that a third factor – an irresistible impulse brought about by mental illness – which the court said "debarred [the defendant] from refraining from committing the act", may also be taken into account. This extension of the rules to comprehend a new criterion of volitional control goes further than a strict interpretation of the M'Naghten rules would have allowed. Thus, Irish law seems to be more aligned with the formulation of insanity as set out by Sir James Fitzjames Stephen in his Digest of the Criminal Law in 1891 – an early attempt in Victorian days to provide a codification of the criminal law – which admits of the possibility of a disease of the mind preventing a person from controlling his or her conduct. It is interesting to note that Sir James Fitzjames Stephen codified the English criminal law, as I am currently engaged in a similar project with regard to our domestic law. Mr. Finbar McCauley, to whom I referred earlier, is chairman of a working group that is embarking upon that exact task.