People with serious mental illness are incarcerated at rates far exceeding their share of the general population. The Bureau of Justice Statistics has estimated that more than half of all prison and jail inmates have a mental health problem. Substance use disorders are even more prevalent: studies consistently find that the majority of people arrested test positive for drugs at the time of arrest, and that substance use disorders are among the strongest predictors of recidivism.

The pathways from mental illness to justice contact are multiple. People in psychiatric crisis may behave in ways that attract police attention — disturbing the peace, trespassing, or acting erratically in public. Officers who encounter individuals in crisis must make rapid decisions with limited information and limited options. The criminalization of mental illness is partly a consequence of deinstitutionalization — the closure of state psychiatric hospitals beginning in the 1960s — which shifted responsibility for mental health crises to communities that were not adequately resourced to respond.

Crisis Intervention Team (CIT) training, developed in Memphis in 1988, provides officers with 40 hours of training in mental health recognition, de-escalation, and community resources. CIT programs have been widely adopted, but the evidence on their effectiveness is mixed. Studies have found that CIT-trained officers are more likely to refer individuals to mental health services and less likely to use force in some contexts, but the evidence on arrest rates and officer safety is less consistent.

Co-responder programs pair police officers with mental health clinicians to respond to crisis calls together. These programs allow clinicians to conduct assessments and connect individuals to services while officers manage safety. Some jurisdictions have implemented civilian-only response programs for lower-acuity mental health calls, removing police from the initial response entirely. The evidence on these models is promising but limited, and the appropriate model depends on the nature of the call, available resources, and community context.

Mental health courts are specialized courts that divert defendants with mental illness from traditional prosecution into treatment-based supervision. Participants who complete treatment requirements may have charges dismissed or reduced. Meta-analyses have found that mental health courts reduce recidivism compared to traditional prosecution, though effect sizes are modest and the quality of available studies varies. Drug courts, which follow a similar model for substance use disorders, have a more extensive evidence base.

Pretrial diversion programs offer individuals with mental illness or substance use disorders an alternative to prosecution before charges are filed. Sequential Intercept Model (SIM) frameworks identify multiple points in the justice system where diversion is possible, from initial police contact through reentry from incarceration. The SIM provides a planning tool for communities to identify gaps in their diversion infrastructure and develop targeted responses.

Treatment access is a persistent barrier. Many jails and prisons do not provide adequate mental health treatment or medication-assisted treatment for opioid use disorder, despite evidence that these treatments reduce both health harms and recidivism. The abrupt discontinuation of psychiatric medications upon incarceration can precipitate crises. Upon release, individuals face gaps in insurance coverage, waiting lists for community mental health services, and the loss of housing and social supports that are essential for treatment engagement.

The policy debate over criminalization versus treatment reflects deeper disagreements about the appropriate role of the criminal justice system. Critics of criminalization argue that jails and prisons are inappropriate settings for mental health treatment and that justice involvement makes recovery harder. Defenders of the current system argue that the criminal justice system provides a point of contact for individuals who would otherwise not engage with treatment, and that supervision conditions can motivate treatment engagement. Both positions have some empirical support.

Steadman, H. J., Osher, F. C., Robbins, P. C., Case, B., & Samuels, S. (2009). Prevalence of serious mental illness among jail inmates. Psychiatric Services, 60(6), 761–765.

Compton, M. T., Bahora, M., Watson, A. C., & Oliva, J. R. (2008). A comprehensive review of extant research on Crisis Intervention Team (CIT) programs. Journal of the American Academy of Psychiatry and the Law, 36(1), 47–55.

Lowenkamp, C. T., Holsinger, A. M., & Latessa, E. J. (2005). Are drug courts effective? A meta-analytic review. Journal of Community Corrections, 15(1), 5–11.

Collins, S. E., Lonczak, H. S., & Clifasefi, S. L. (2017). Seattle's Law Enforcement Assisted Diversion (LEAD): Program effects on recidivism outcomes. Evaluation and Program Planning, 64, 49–56.

Substance Abuse and Mental Health Services Administration. (2019). SAMHSA's Concept of Trauma and Guidance for a Trauma-Informed Approach. https://store.samhsa.gov/product/SAMHSA-s-Concept-of-Trauma-and-Guidance-for-a-Trauma-Informed-Approach/SMA14-4884