Origin Formulated by the House of Lords in 1843, following the acquittal of Daniel M'Naghten for the killing of Edward Drummond.
The M'Naghten Rules are the classic common law test for the insanity defense in criminal law, asking whether, at the time of the act, the 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, or, if he did know it, that he did not know it was wrong. The rules take their name from Daniel M'Naghten, acquitted by reason of insanity in 1843 after shooting Edward Drummond, private secretary to the British prime minister Sir Robert Peel, whom M'Naghten had mistaken for Peel himself; the acquittal provoked public outrage, and the House of Lords responded by convening the judges to answer a set of hypothetical questions on the insanity defense, whose answers became the Rules. The Rules remain the established standard in English criminal law and have been adopted, in whole or modified form, by a number of United States states, while other jurisdictions apply different tests such as the Model Penal Code substantial-capacity test or have abolished an independent insanity defense altogether. This description is adapted from Wikipedia contributors under CC BY-SA 4.0; changes were made. https://creativecommons.org/licenses/by-sa/4.0/
Facts
Disputed
Core PrincipleWhether the M'Naghten Rules remain the right test for criminal insanity is a live and unsettled question: some United States states use it as adopted, others have replaced it with the Model Penal Code's broader substantial-capacity test, which excuses a defendant who lacks substantial capacity either to appreciate the wrongfulness of the conduct or to conform conduct to the law, and a handful of states, including Kansas, Montana, Idaho and Utah, have abolished an independent insanity defense altogether, permitting mental illness to be raised only to negate the required mental state (mens rea). 1 Which test best balances moral culpability against the reality of mental illness remains genuinely contested among criminal law scholars and legislatures, evidenced by the continuing split among jurisdictions. Origin PeriodFormulated by the House of Lords in 1843, following the acquittal of Daniel M'Naghten for the killing of Edward Drummond. 1 Core PrincipleEvery man is presumed sane; to establish an insanity defense it must be clearly proved that, at the time of the act, the 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 he was doing what was wrong. 1 The House of Lords' 1843 answer to the judges' questions following the M'Naghten acquittal, the Rules' own classic wording. Origin Period
Origin Period (category)19th Century (1800-1899) 1 Classification
Doctrine Category Connections
In Area Of Law
Entity-backed identity for the doctrine category value this doctrine already carries as an enum fact, resolved to a doctrine entity by an explicit value-to-entity map (phase 3 bucket conversion, docs\design_entity_backed_browse_buckets_20260928.md). The enum fact itself stays on the entity unchanged.
Held Differently
Civil Law, Legal Systems Civil law systems generally excuse a mentally disordered defendant through their own non-responsibility provisions (for example Article 122-1 of the French Penal Code), a differently framed doctrine reaching a broadly similar result rather than the M'Naghten test itself.
Source M'Naghten Rules (Wikipedia)
In Legal System
Source M'Naghten Rules (Wikipedia)
In the Other Atlases
Sources
1. M'Naghten Rules (Wikipedia)
Overview
The M'Naghten rule(s) (pronounced, and sometimes spelled, McNaughton) is/are a legal test defining the defence of insanity that was formulated by the House of Lords in 1843. It is the established standard in UK criminal law.
The Rules
the jurors ought to be told in all cases that every man is to be presumed to be sane, and to possess a sufficient degree of reason to be responsible for his crimes, until the contrary be proved to their satisfaction; and that to establish a defence on the ground of insanity, it must be clearly proved that, at the time of the committing of 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 he was doing what was wrong.
History
The rule was created in reaction to the acquittal in 1843 of Daniel M'Naghten on the charge of murdering Edward Drummond. M'Naghten had shot Drummond after mistakenly identifying him as the British Prime Minister Robert Peel, who was the intended target.
Alternative rules section, adoption by US jurisdictions
The insanity defence article has a number of alternative tests that have been used at different times and places. As one example, the ALI test replaced the M'Naghten rule in many parts of the United States for many years until the 1980s; when, in the aftermath of John Hinckley shooting US President Ronald Reagan, many ALI states returned to a variation of M'Naghten.
- a legal test defining the defence of insanity
- In Legal System: Common Law
- In Legal System: Civil Law
View the SourceFrequently Asked Questions
Is a defendant presumed sane under the M'Naghten Rules?
Yes: sanity is presumed until the defence proves a defect of reason from disease of the mind.
Yes. The rules direct that jurors be told that every man is presumed to be sane and to possess a sufficient degree of reason to be responsible for his crimes, until the contrary is proved to their satisfaction. To establish insanity, it must be clearly proved that at the time of the act the 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, or, if he did know it, not to know that it was wrong.
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