Insanity defense (M'Naghten rule)
← the full American Legal Lexicon
Insanity defense (M'Naghten rule) criminal
A defense that a person shouldn't be held criminally responsible because, due to mental illness, they didn't know what they were doing or didn't know it was wrong.
Technical: Under the M'Naghten rule, a defendant is legally insane if, from a disease of the mind, he did not know the nature and quality of the act, or did not know it was wrong; adopted from M'Naghten's Case, 8 Eng. Rep. 718, 10 Cl. & Fin. 200 (H.L. 1843).
Founding-era note: A leading example of an English decision received as persuasive authority: M'Naghten's Case (1843) was decided by the British House of Lords yet became the insanity-defense standard in many U.S. jurisdictions.
A dictionary entry is reference: it describes how a term is used. It is not itself binding law. Why that matters →
Act on this
Somewhere to act on what you just read — start with our own tools:
Find a lawyer or legal aid → · File a complaint / get help → · Appeals, writs & exhausting remedies → · Search the caselaw & statutes → · Legal doctrines →
Legal information, not legal advice.