Agency and Insanity

The criminal law test for insanity has evolved over centuries, yet fundamental questions about what insanity means remain unresolved. Garvey revisits Daniel M'Naghten's 1843 assassination attempt on Prime Minister Peel, which generated the M'Naghten Rule—the modern legal standard equating insanity with cognitive incapacity. The article traces how M'Naghten was delusional: he believed Tories were persecuting him and killing was the only escape. Chief Justice Tindal instructed acquittal based on insanity, establishing the rule that lost sense of agency—a lost agency theory—may constitute insanity. Garvey proposes that insanity should be understood as a defect of consciousness, specifically as lost sense of agency comparable to other consciousness defects like sleepwalking and hypnosis. If insanity involves lost agency, then paradoxically it wasn't really M'Naghten who killed Edmund Drummond because M'Naghten lacked authorship of his thoughts and actions. The article develops two versions of the irrationality test and finds them wanting before introducing insanity as lost agency. Garvey argues this theory accounts for the intuition that M'Naghten was insane while explaining why cognitive capacity tests alone cannot capture insanity's essence. The analysis bridges criminal responsibility doctrine with philosophy of mind.

Topics: Criminal Procedure · Legal Theory · Constitutional Law

Keywords: M'Naghten Rule · insanity defense · agency · lost agency theory · consciousness · criminal responsibility · cognitive incapacity