This November, a Minnesota man was found not guilty by reason of insanity after stabbing and suffocating his 71-year-old mother.  One week earlier, an Illinois man was sentenced to 56 years in prison after being found guilty but mentally ill in the murder of a local woman. 
Cases of defendants with mental illnesses receiving lengthy punitive sentences are far from rare in the United States. A 2005 report by the Bureau of Justice Statistics, for example, found that more than half of all U.S. prison and jail inmates had a mental health problem. Despite the prevalence of mental illness among prisoners, only a small amount of those prisoners had been deemed officially mentally ill by the courts that sentenced them. Today, mental illness is all but ignored by courts and prisons as a major contributing factor towards who commits crimes.
There are three possible outcomes in cases where a defendant uses the insanity plea: one can be found guilty, guilty but mentally ill (GBMI), or not guilty by reason of insanity (NGRI). Someone is defined as GMBI when they are determined to have been mentally ill, but not insane, at the time that they committed the crime. When someone is found GBMI, they can receive “any sentence which the defendant could have received by virtue of being found guilty.” Once entering a correctional facility, the prisoner then receives appropriate treatment, if it is available (and often, it is not).
When the court determines that a was not sane at the time of the offense, the person is deemed NGRI, and the insanity plea is accepted. The basis of the insanity defense is “the assumption that those who commit criminal acts while insane should not be held criminally responsible for their behavior.”
In their current form, the accepted definitions of mental illness in the U.S. justice system are too strict and too narrow to account for the large amounts of defendants struggling with drug abuse and mental health problems. These definitions are problematic because they fail to take into account defendants’ backgrounds, and the reasons the defendant might have become involved in crime.
This research and these statistics tell part of the story that traps many defendants in a cycle of crime and incarceration—people born into families and neighborhoods that expose them to physical or sexual abuse are more likely to develop a mental health problem, people with mental health problems are more likely to use drugs, and people who use drugs are more likely to become incarcerated. Of course, people do not choose the situations into which they are born, and if certain circumstances make it more likely for people to be incarcerated later on, it is unjust for the legal system to fail to make efforts to ameliorate these disadvantages.
It is also important to take history into account when looking at how mental illness is regarded in courts. In the 1950s and 60s, public dissatisfaction with the idea of inhumane mental institutions was growing. As a result, President Kennedy signed the Community Mental Health Act in 1963, which authorized federal grants to build community mental health centers intended to replace state-run institutions. The final version of the bill, however, provided only minimal funding for states to establish the new community facilities, and no funding at all for hiring staff. This act marked the beginning of “deinstitutionalization.” Some have hypothesized that as patients started getting released from hospitals, and as fewer new patients were accepted, former “mental patients who [caused] trouble in the community often [were] arrested to get them off the streets,” contributing to the movement of the mentally ill out of their communities and into prisons. The relationship between deinstitutionalization and the increase in prison and jail populations has since been widely accepted. One report notes that “at the end of 1968, there were 399,000 patients in state mental hospitals and 168,000 inmates in state prisons. Within a decade, the hospital population fell 64%, to 147,000, while the prison population rose 65%, to 277,000." 
Furthermore, lengthy punitive sentences given to many inmates, mentally ill or not, and the conditions of the prisons themselves, can be much more harmful to the individual and to society than they are helpful. According to the World Health Organization (WHO), prisons are harmful to inmates’ mental health because of “overcrowding, various forms of violence, enforced solitude or conversely, lack of privacy, lack of meaningful activity, isolation from social networks, insecurity about future prospects (work, relationships, etc.), and inadequate health services, especially mental health services.”
While the future of treating—or failing to treat—mental illness is difficult to predict, the mere existence of the insanity defense shows that the U.S. has at least some desire to rehabilitate, rather than punish, mentally ill prisoners. There seems to be a general consensus that the majority of mentally ill criminals do not belong in prisons, and when individuals with mental illness do end up in prisons, they should be treated, not punished. While prisons are the only place in America where people are guaranteed healthcare, this care is often not great. Furthermore, there is more to promoting mental health than just having access to doctors and medications. Today in America, there are inadequate facilities to care for people with mental illnesses in the community in the place of prisons, and an inadequate distribution of funds to provide sufficient mental health services to inmates who need them. If we ever locate the money to do so, rehabilitative sentences should take the place of punitive ones, and should be required for all defendants found guilty of non-violent crimes. Extending the chance of rehabilitation to all inmates with and without mental illness and addiction problems will, in the long run, help reduce the proportion of people from disadvantaged groups who are incarcerated in the United States.
 Tom Olson. Duluth man who stabbed, suffocated mother is found mentally ill, not guilty. Pioneer Press, 29 November 2016.
 Lee V. Gaines. Man who killed island lake woman sentenced to 56 years in prison. Chicago Tribune, 23 November 2016.
 Doris J. James and Lauren E. Glaze. Mental Health Problems of Prison and Jail Inmates. Bureau of Justice Statistics. 14 December 2006.
 Callahan, Lisa; Steadman, Henry; McGreevy, Margaret; Robbins, Pamela Clark. The Volume and Characteristics of Insanity Defense Pleas: An Eight-State Study. The Bulletin of the American Academy of Psychiatry and the Law. Vol. 19, No. 4, 1991. Retrieved from http://jaapl.org/content/jaapl/19/4/331.full.pdf
 Barbara A. Weiner, J.D. The Insanity Defense: Historical Development and Present Status. Behavioral Sciences & the Law, Vol. 3, No. 1:3-35 (Winter 1985)
 Norko, Wasser, Magro, Leavitt-Smith, Morton, and Hollis. Assessing Insanity Acquittee Recidivism in Connecticut. Behavioral Sciences and the Law. Published online 8 April 2016 in Wiley Online Library.
 See Norko et al., note 6.
 See Weiner, note 5.
 See Weiner, note 5.
 V. Plaut. Punishment versus Treatment of the Guilty but Mentally Ill. Journal of Criminal Law and Criminology, Volume 72 Issue 2. Summer 1983.
 See James and Glaze, note 3.
Steadman, Henry J.; Monahan, John; Duffee, Barbara; Hartstone, Eliot; Robbins, Pamela Clark. The Impact of State Mental Hospital Deinstitutionalization on United States prison populations, 1968-1978. The Journal of Criminal Law and Criminology, 1984, Volume 75 number 2.
 See James and Glaze, note 3.
World Health Organization and ICRC. Information Sheet: Mental Health and Prisons.
 See Weiner, note 5.