Objective  This study sought to describe patterns and costs of criminal justice involvement among adults with serious mental illness who received services across public agencies within a single state. Costs were examined from the perspective of state agencies providing mental health, substance abuse, and criminal justice services.

Methods  Administrative records for 25,133 adults who were served by the Connecticut Department of Mental Health and Addiction Services (DMHAS) during fiscal years 2006 and 2007 and who had a diagnosis of schizophrenia or bipolar disorder were matched with records of the state Medicaid program, Judicial Branch, Department of Correction, and Department of Public Safety. Unit costs for service events were combined with utilization data to calculate costs per person.

Results  About one in four individuals was involved with the justice system during the two-year period. The justice-involved group incurred costs approximately double those of the group with no involvement—$48,980 compared with $24,728 per person. Costs were shared by several state agencies and Medicaid. DMHAS bore the largest proportion of state service costs, covering 49% of total costs for persons with justice involvement and 69% of costs for those without involvement.

Conclusions  Criminal justice involvement is a complex and costly problem that affects a substantial proportion of adults with serious mental illness who receive services across state agencies. Applying per-person cost estimates in other states could help mental health and criminal justice systems to better plan, coordinate, and deliver cost-effective services to individuals with serious mental illness who become involved with the criminal justice system.