Professional
Formal
IVT
M'Naghten rule
Pronunciation: mək-NOT-ən
Legal standard for insanity defense requiring proof that defendant did not understand the nature or wrongfulness of their acts.
Full Definition
The traditional common law test for criminal insanity, established in M'Naghten's Case (1843), which requires the defense to prove that at the time of the offense, the defendant was laboring under such a defect of reason from disease of mind as not to know the nature and quality of the act, or if they did know it, that they did not know what they were doing was wrong. This cognitive test focuses on the defendant's understanding rather than their ability to control behavior.
Usage
Usage note: Note the apostrophe placement and Scottish spelling of the name.
In Context
- "The jurisdiction applies the M'Naghten rule, requiring proof the defendant could not distinguish right from wrong." — Expert testimony
- "Under the M'Naghten rule, mere mental illness is insufficient without cognitive impairment." — Legal analysis
Also known as
right-wrong test
cognitive test
Contrasted with
irresistible impulse test
volitional test
Don't confuse with
ALI standard
Durham rule