Under the M'Naghten rule, insanity requires that the defendant lacks the ability to

• A. Understand the nature and quality of the act and appreciate the wrongfulness
• B. Understand the nature and quality of the act
• C. Appreciate the wrongfulness of the act
• D. Lack any understanding due to intoxication

Answer: (A)

Under the M'Naghten rule, insanity is judged by the defendant’s cognitive awareness at the time of the act. The test requires that the defendant either does not understand the nature and quality of the act, or, if they do understand, they do not understand that what they are doing is wrong. That combination is why the option stating they lack the ability to understand the nature and quality of the act and to appreciate the wrongfulness best matches the rule. If a person understands the act but believes it is not wrong, or if they do not understand what they are doing at all, both prongs would be relevant to the defense. Intoxication is not the M'Naghten standard for insanity.