Daniel M'Naghten - Significance

Significance

The verdict in M'Naghten's trial provoked an outcry in the press and Parliament. Queen Victoria, who had been the target of assassination attempts, wrote to the prime minister expressing her concern at the verdict and the House of Lords revived an ancient right to put questions to judges. Five questions relating to crimes committed by individuals with delusions were put to the twelve judges of the Court of Common Pleas. One of the judges – Mr Justice Maule – declined to answer; Chief Justice Tindal delivered the unanimous answers of the other eleven to the House of Lords 19 June 1843. The answer to one of the questions became enshrined in law as the M'Naghten Rules and stated:

To establish a defence on the ground of insanity it must be clearly proved, that, at the time of committing the act, the party accused was labouring under such a defect of reason from disease of the mind, as not to know the nature and quality of the act he was doing, or if he did know it, that he did not know that what he was doing was wrong.

The rules dominated the law on criminal responsibility in England and Wales, the United States, and many countries throughout the British Commonwealth for over 100 years. In England and Wales the defence of insanity to which the rules apply was largely superseded, in cases of murder, by the Scottish concept of diminished responsibility, following the passage of the Homicide Act 1957.

M'Naghten's defence had successfully argued that he was not legally responsible for an act which arose from a delusion; the rules represented a step backwards to the traditional 'knowing right from wrong' test of criminal insanity. Had the rules been applied in M'Naghten's own case, the verdict might have been different. One of M'Naghten's younger half-brothers, Thomas McNaughtan, a doctor, became mayor of Blackpool and was a magistrate.