Those who are mentally ill at the time of the commission of a crime may be found “insane” or not guilty by reason of insanity (or mental disease or defect, depending on jurisdiction). Rather than going to prison, the individual is sent to a hospital where they receive treatment. Individuals who are found guilty may face life in prison or even the death penalty. So is the insanity defense fair? Is the insanity defense necessary? Based on the consequences (prison vs. hospitalization) of a criminal act, there might seem to be an unfair bias toward those with mental illness. It may also seem that those with mental illness are using their symptoms as an empty justification for the crimes they have committed. So why is the insanity defense allowed?
To put it simply, people are typically punished if they do something wrong that they meant to do. If you killed someone (a wrongful act) but did not intend to do so (no intent), you are unlikely to be charged with murder. Similarly, if you meant to kill someone on purpose (intent), but it was in self-defense or combat (no wrongdoing), you would also not be charged with murder. Although there can be exceptions to this rule, generally speaking, people are punished in our criminal justice system when they commit wrongful acts which they intend to do and are capable of recognizing as wrong. Our society typically makes exceptions for those who do not understand what is wrong. One example is children. A four-year-old who shoots and kills his brother is unlikely to stand trial for murder because it is generally accepted that a four-year-old lacks the mental capacity to appreciate what he has done. Though certainly different from a four year old, some mentally ill individuals commit crimes for which they cannot appreciate the wrongfulness of their action or because they are unable to control their behavior.
The Courts in the United States have frequently cited “retribution” and “deterrence” as explanations for why punishment is necessary for criminals. These same Courts have also stated that punishment for a person who cannot understand the wrongfulness of their actions will not be impacted by retribution and deterrence. The punishment would not serve a purpose. A mentally ill person who cannot understand that their actions are harming others will not be deterred from engaging in harmful behavior in the future, despite punishment received in the past. Similarly, a severely intellectually disabled individual may be unable to benefit from learning of the punishment other intellectually disabled individuals have received following the commission of a crime they are about to commit. Although these individuals will need treatment and may need to be separated from society, it does not need to be done in a punitive setting or fashion.
It is also worth noting that the insanity plea is rarely made and even less often successful. Although numbers range depending on the year or jurisdiction, only about 0.1% to 0.5% of criminal cases in many states raise the issue of insanity. The success rate also varies, particularly because the standard for insanity differs between states. However, the national success rate of those cases which raise the insanity defense is estimated to be around 25%. This suggests that even in states for which the insanity defense is raised more often, less than 1% of individuals with criminal felony charges are found Not Guilty by Reason of Insanity.