McNaghten Rule Definition and Legal Meaning

On this page, you'll find the legal definition and meaning of McNaghten Rule, written in plain English, along with examples of how it is used.

What is McNaghten Rule?

(n) McNaghteen Rule applies to a person who cannot identify or understand the right or wrong classification of an event or action while doing an act involving crime, showing the insanity of their mind at the time of crime

History and Meaning of McNaghten Rule

The McNaghten Rule is a legal test for the criminal responsibility of individuals who commit crimes while suffering from mental disorders. It was established in England in 1843 following the failed assassination attempt on Prime Minister Sir Robert Peel by Daniel McNaghten. McNaghten was found not guilty by reason of insanity, and the verdict of the case led to the formulation of the McNaghten Rule. According to the rule, a person is not held criminally liable if, at the time of committing the act, they were suffering from a mental disorder that prevented them from understanding the nature and quality of their actions or distinguishing right from wrong.

The McNaghten Rule has been the basis of the insanity defense in many common law jurisdictions, including most states in the United States. However, the test has been subject to criticism due to its narrow focus on cognitive incapacity and lack of consideration of the individual's volitional control over their actions. Several jurisdictions have since modified the rule to include volitional incapacity, where individuals are not held responsible for their actions if they were unable to control them due to their mental disorder.

Examples of McNaghten Rule

  1. John was diagnosed with schizophrenia and believed that he was receiving commands from aliens to kill his neighbor. He stabbed his neighbor to death while in a delusional state. John may be found not guilty by reason of insanity under the McNaghten Rule.

  2. Maria suffered a traumatic brain injury that resulted in her inability to understand right from wrong. She was unaware that the counterfeit money she was using to purchase goods was illegal. Maria may be found not guilty by reason of insanity under the McNaghten Rule.

  3. George was diagnosed with bipolar disorder and was experiencing a manic episode when he broke into his ex-girlfriend's house and vandalized her car. He later testified that he had no recollection of the incident. George may not be found not guilty by reason of insanity under the McNaghten Rule because his behavior was not a result of his inability to understand right from wrong.

Legal Terms Similar to McNaghten Rule

  1. Durham Rule: A legal test used in some U.S. jurisdictions that holds a person not responsible if their criminal behavior was the result of a mental disease or defect.

  2. Model Penal Code: A proposed set of laws developed by the American Law Institute that includes a comprehensive test for insanity, which takes into account both cognitive and volitional incapacity.

  3. Irresistible Impulse Test: A variation of the McNaghten Rule used in some U.S. jurisdictions that excuses defendants from criminal responsibility if they were unable to control their behavior due to a mental illness.