The M’Naghten test excuses defendants who cannot know their act was wrong.

Evidence

Under the M’Naghten test, a defendant is responsible for criminal actions unless “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, he did not know he was doing what was wrong.”*? Thus, ity must es What is distinctive about the M’Naghten test is its emphasis on theeognitivecapaeity of defendants-that is, their ability to distinguish right from wrong. — G. Alan Tarr, Judicial Process and Judicial…, 1882

Categorization

• DEFINE: Quotes the canonical M’Naghten formulation verbatim — the doctrinal language itself.
• XREF: Pairs directly with the cognitive vs. volitional distinction developed in the following paragraphs.