Do you think that the mental disorders that can be considered in a defense of diminished capacity should be limited and defined by statute? Why or why not? If you favor limiting mental disorders, which ones would you limit it to?

To a certain extent, criminal insanity is defined by each state according to its own adherence to any of several tests or definitions. About one-half of the states use what is called the “M’Naghten Rule,” which has its origins in 19th century British law. This rule applies a standard by which a criminal defendant can plead insanity by proving that he or she was mentally incapable of differentiating between right and wrong or that he or she was unaware that he or she was committing the criminal act in question. Most of the rest of the country uses the Model Penal Code criteria developed by the American Law Institute, which requires the defendant to prove that he or she was temporarily mentally incapacitated and therefore incapable of determining the legality of his or her actions. In addition to the M’Naghten Rule, which has its origins in 19th century British law, and the Model Penal Code, there is also the Durham rule, which dates to the 1950s.
In response to the question as to whether the insanity or diminished capacity defenses should be limited by statute, they pretty much already are by virtue of their institutionalization in criminal law. Only four of the 50 states do not allow for an insanity defense, while the other 46 have adopted one of the above variations. There is a serious lack of uniformity across the nation with respect to the insanity defense, but defining psychological or physiological disorders that impair judgement in statute is much harder than it sounds. The insanity defense is more a product of common than statutory law and is likely to remain so indefinitely for two reasons. The first reason is the individual states’ reluctance to have elements of their criminal law structures altered by federal action. The second reason is the near impossibility of defining insanity in such a way as to preclude misinterpretations or misapplications of any such law. Even well-written laws are susceptible to manipulation by lawyers and others. Defining insanity for the purposes of criminal law would be fraught with complications.
This educator would be extremely hesitant to limit the definitions of mental disorders for the purpose of refining criminal law. There are simply too many variables involved. Was the mental disorder caused by an operable tumor as opposed to an inoperable one? Did the defendant fail to distinguish between right and wrong because of a prescribed medication that impaired judgement? As to whether this educator would limit mental disorders that can be used to excuse criminal behavior, the answer is no. While there has inarguably been abuse of the insanity defense, the perils of imposing such limitations are too great to allow for such an exercise in micromanagement of medical conditions.