What is the basis for the "insanity" defense in Missouri criminal law?

The "insanity" defense in Missouri criminal law is rooted in the principle that a defendant cannot be held criminally responsible for their actions if they were unable to understand the nature and quality of their acts or to distinguish right from wrong at the time of the offense due to a severe mental disorder. This is a reflection of the belief that culpability requires a certain level of mental competency and awareness. When a defendant successfully raises this defense, it indicates that their mental state prevented them from comprehending the consequences of their actions, thereby absolving them of legal responsibility for the crime committed. This standard is generally assessed through psychological evaluations and expert testimony during the trial process, focusing on the defendant's mental condition at the time the crime was committed.

The other provided options do not align with the legal definition of the insanity defense. The emotional state during the crime, prior criminal history, and the defendant's age may all influence various aspects of a case or mitigating factors but do not form the basis for establishing an insanity defense under Missouri law. The emphasis is specifically on the mental disorder's impact on the defendant’s cognitive and moral understanding during the commission of the alleged crime.