M'Naughten's Case, 8 Eng. Rep. 718 (H.L. 1843)

  • Facts: Daniel M'Naughten, suffering from paranoid delusions that the British Tory government was persecuting him, attempted to assassinate Prime Minister Robert Peel and instead shot and killed Peel's secretary, Edward Drummond. M'Naughten was acquitted on grounds of insanity. The acquittal caused public outcry; the House of Lords formulated a set of "rules" to clarify the insanity defense going forward.
  • Issue: What is the proper test for the insanity defense in criminal cases?
  • Rule: To establish insanity, ∆ must show that, at the time of the act, ∆ was laboring under such a defect of reason from disease of the mind as to either:
    • Not know the nature and quality of the act, OR
    • If ∆ knew the nature and quality, not know that the act was wrong.
  • Analysis: This "right and wrong" test is purely cognitive—it does not excuse those who knew the act was wrong but could not control themselves (volitional component added in some jurisdictions via the "irresistible impulse" supplement).
  • Judgment: M'Naughten Rules promulgated; foundation of CL insanity doctrine.

Reading: pp. 696–704. See Insanity.