The impact on taxpayer costs of a jail diversion program for people with serious mental illness

• Mental illness is prevalent among those incarcerated.
• Jail diversion could help treat people with mental illness instead of incarcerating them, and save taxpayer costs.
• This study estimates the impact on taxpayer costs of a model jail diversion program for people with serious mental illness.
• Propensity score methods and a quasi-experimental design were used on a combination of administrative, primary, and secondary data.
• Diversion was associated with approximately $2800 lower taxpayer costs per person 2 years after the point of diversion (p < .05). Reductions in criminal justice costs drove this result.

Mental illness is prevalent among those incarcerated. Jail diversion is one means by which people with mental illness are treated in the community – often with some criminal justice system oversight – instead of being incarcerated. Jail diversion may lead to immediate reductions in taxpayer costs because the person is no longer significantly engaged with the criminal justice system. It may also lead to longer term reductions in costs because effective treatment may ameliorate symptoms, reduce the number of future offenses, and thus subsequent arrests and incarceration. This study estimates the impact on taxpayer costs of a model jail diversion program for people with serious mental illness. Administrative data on criminal justice and treatment events were combined with primary and secondary data on the costs of each event. Propensity score methods and a quasi-experimental design were used to compare treatment and criminal justice costs for a group of people who were diverted to a group of people who were not diverted. Diversion was associated with approximately $2800 lower taxpayer costs per person 2 years after the point of diversion (p < .05). Reductions in criminal justice costs drove this result. Jail diversion for people with mental illness may thus be justified fiscally.