anity defense is asserted when a criminal defendant has been charged with a crime that of which the defendant admitted that they have committed, but lacks culpability based upon impairment from mental illness (Cornell Law). For a defendant to plea insanity, they “must prove to the court that they didn’t understand what they were doing; failed to know right from wrong; acted on an uncontrollable impulse; or some variety of these factors” (FindLaw). Whether or not the defendant is guilty or not guilty by reason of insanity, the courts use one or more of the following tests to determine legal insanity: The M’Naghten Rule, The Irresistible Impulse Test, The Durham Rule and The Model Penal Code Test (FindLaw). Based upon the results of these tests can result in a successful defense as well as capacity evidence, volitional control and mental disease evidence (Knoll & Resnick).

Although there are tests to determine legal insanity, there is a demographic of people that are often acquitted based upon insanity. The demographic of individuals acquitted from insanity show that “the average defendant is male, between the ages of 20 and 29, unmarried, unemployed, minimally educated and has been acquitted for a violent offense and diagnosed with a major mental illness based upon prior contact with both the criminal and mental health systems” (Lymburner & Roesch). The presence of a mental disease that renders the defendant’s mental capacity of meeting legal criteria for responsibility plays a relevant role in determining criminal responsibility (Lymburner & Roesch).

Research provided by Lymburner & Roesch (1997) shows that defendants who are not criminally responsible by reason of insanity were diagnosed with psychotic disorde