What does the MPC Insanity Test require for someone to be considered insane?

Under the Model Penal Code (MPC) insanity test, a defendant is considered insane if they lacked substantial capacity to appreciate the criminality of their conduct or to conform their conduct to the requirements of the law due to a mental disease or defect. This approach emphasizes the defendant's ability to understand the nature of their actions and to recognize that those actions are wrong.

The focus on substantial capacity, rather than a complete inability to understand right from wrong, reflects a more nuanced understanding of mental illness and how it can affect behavior. This definition allows for individuals who may understand the nature of their actions but, due to a mental health condition, cannot adequately control their behavior in relation to the law.

The other options, while related to mental health issues, do not align with the MPC standard. Prior historical insane behavior, a history of mental illness, or merely the inability to differentiate between right and wrong do not fully capture the essence of the MPC's criteria for legal insanity. The key factor is the absence of substantial capacity, which encompasses both appreciation of criminality and the ability to conform conduct to the law.