Categorizing temporal patterns of arrest in a cohort of adults with serious mental illness.

Temporal patterns of arrest among mental health systems' clientele have not been well explored. This study uses "trajectory analysis," a methodology widely employed by criminologists exploring patterns of desistence in offending, to examine patterns of criminal justice involvement in a cohort of mental health service recipients. Data for this study are from a statewide cohort of individuals who received services from the Massachusetts Department of Mental Health in 1991 (N = 13,876) and whose arrests were followed for roughly 10 years. Zero-inflated Poisson trajectory analysis applied to cohort members having two or more arrests identified five trajectories with widely varying arrest patterns. Analysis of differences in the composition of the five trajectory-based groups revealed few between-group differences in members' demographic and service use characteristics, while certain offense types were disproportionately prevalent among particular trajectory-based groups. The implications of these findings for understanding criminal justice involvement in this population and the utility of the trajectory model for system planning are discussed.