A woman, suffering from a severe mental illness, believes that her neighbor is a demon sent to destroy the world. Acting on this delusion, she attacks her neighbor with a kitchen knife, inflicting serious injuries. She genuinely believes she is saving humanity. In a jurisdiction applying the M'Naghten rule for insanity, what is the most likely outcome?
- AGuilty of voluntary manslaughter, due to extreme emotional disturbance.
- BGuilty but mentally ill, as her mental illness caused the act.
- CGuilty, as she intended to harm her neighbor.
- DNot guilty by reason of insanity, as she did not know the nature and quality of her act or that it was wrong.
Show answer & explanationAnswer & explanation
Correct answer: D. Not guilty by reason of insanity, as she did not know the nature and quality of her act or that it was wrong.
The M'Naghten rule dictates that a defendant is not guilty by reason of insanity if, at the time of committing the act, they were laboring under such a defect of reason, from disease of the mind, as not to know the nature and quality of the act they were doing, or, if they did know it, that they did not know what they were doing was wrong. Believing her neighbor is a demon and she is saving humanity falls squarely under not knowing the act was morally or legally wrong.
Why the other options are wrong
- A. Voluntary manslaughter involves heat of passion, not a complete defense based on mental disease negating culpability.
- B. Guilty but mentally ill is a statutory verdict in some jurisdictions, but M'Naghten is a standard for outright acquittal by reason of insanity.
- C. While she intended the physical act, her delusion negates the understanding of its wrongfulness under M'Naghten.
M'Naghten Rule
A test for criminal insanity that asks whether the defendant, at the time of the crime, was laboring 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, that he did not know what he was doing was wrong.
- Focuses on cognitive capacity (knowing right from wrong)
- Requires a 'disease of the mind'
- Defendant must not know nature/quality of act OR that it was wrong
- The most restrictive insanity defense test
Memory trick: Insanity's path: M'Naghten's mind, irresistible's push, or MPC's blend you'll find.