M'Naghten Rules
Definition
The 1843 English House of Lords formulation providing that a defendant is not criminally responsible if, at the time of the offence, by reason of disease of the mind, they did not know the nature and quality of their act, or did not know that it was wrong.
- Origin
- 1843 English House of Lords
- Core test
- Did not know the nature and quality of the act, or that it was wrong
- Trigger
- Reason of disease of the mind
- Legacy
- Basis for later insanity standards worldwide
Common questions
How does the M'Naghten test differ from an irresistible-impulse standard?+
M'Naghten focuses purely on cognitive knowledge of the act's nature or wrongness, while irresistible-impulse tests additionally excuse a defendant who understood the act was wrong but could not control the urge to commit it, a volitional element M'Naghten does not cover.
Is the M'Naghten standard still used today?+
It remains the governing or foundational standard in England and Wales and several other common-law jurisdictions, though many US states have modified it or adopted alternative tests such as the Model Penal Code standard.
Related terms
- Appreciation vs Knowledge
- The MPC and Canadian Criminal Code use 'appreciate' rather than 'know,' requiring a deeper, emotionally integrated understanding of the nature or wrongfulness...
- BNS § 22
- India's insanity defence provision in the Bharatiya Nyaya Sanhita 2023, replacing IPC § 84: an act is not an offence if done...
- Durham Rule
- The 1954 US Court of Appeals (DC Circuit) product test: an accused is not criminally responsible if the unlawful act was the...
- Guilty but Mentally Ill (GBMI)
- A US verdict alternative introduced in some states from 1975: the defendant is found guilty (and sentenced) but is entitled to psychiatric...
- Hari Singh Gond (2008)
- Indian Supreme Court ruling setting out the four elements for establishing the IPC § 84 (now BNS § 22) defence: mental illness...
- IDRA 1984
- Insanity Defense Reform Act 1984: US federal legislation passed after John Hinckley's acquittal that eliminated the volitional prong, raised the standard to...
- MPC § 4.01 Substantial-Capacity Test
- The American Law Institute's 1962 insanity formulation: a person lacks criminal responsibility if, as a result of mental disease or defect, they...