What is the Irresistible Impulse test in insanity evaluations?

• A. It requires proof the defendant knew the act was illegal and harmful.
• B. It considers whether a mental disease or defect prevented the defendant from controlling their impulses, even if they knew the act was wrong.
• C. It evaluates whether the defendant could resist peer pressure during the act.
• D. It assesses whether the defendant could conform their conduct to the law.

Answer: (B)

This concept centers on volitional inability: the idea that a mental disease or defect can prevent a person from resisting the impulse to commit a crime, even when they understand that the act is wrong. In the Irresistible Impulse test, the key question is whether the illness robbed the defendant of self-control at the moment of the act, not whether they knew that what they were doing was illegal or harmful. So, the best description is that the defendant’s mental condition prevented the ability to restrain impulses, even if they acknowledged the act was wrong.

This differs from requiring knowledge that the act is illegal, which is the focus of the M'Naghten approach. It also isn’t about peer pressure, and while some models talk about conforming conduct to the law, the hallmark of the Irresistible Impulse standard is the loss of control due to mental illness rather than a simple failure to adhere to legal norms.