Project Summary/Abstract Mass incarceration of individuals with serious mental illness (SMI) is a public health and human rights crisis. Not since the mid-nineteenth century has the criminal justice system played such a large role in how American society responds to mental illness. Since the late 1960s researchers have noted ever-rising numbers of jail inmates with SMI, often caught in a "revolving door" of hospitalization, homelessness, and arrest. Incarceration is one of the most visible (and traumatic) moments of contact with the public system, and provides a window into the failures of the public mental health system. Our long-term objective is to inform and rigorously evaluate policy and interventions that seek to reduce law enforcement response to mental illness and end the mass incarceration of individuals with SMI. In line with NIMH Strategic Objectives 4.1B and 4.2, this R34 proposal furthers the development of a real-world data collection system to facilitate research and ongoing monitoring related to access, service continuity, equity, and outcomes such as incarceration and homelessness in diverse populations and settings. Our research approach is to leverage a regularly-updated Los Angeles County (LAC) county-wide administrative database, which links individuals across 8 public agencies from 2010 to the present, for research around incarceration and SMI. In partnership with LAC administrators/providers and non- LAC researchers, we will develop and test this database through algorithm development and validation, exploration of mental health service patterns leading up to incarceration, and testing of the algorithms and dataset using a pilot evaluation of mental health crisis interventions in lieu of law enforcement response, in preparation for an R01 proposal to evaluate the effects of policies and interventions that shift resources from criminal justice to new and existing mental health services. LAC as our study site allows for a particularly in- depth look because of its size (population>10 million) and diversity across a number of critical divides: urban/rural; racial; economic; cultural; and resource availability. Our specific aims are as follows: Aim 1: Develop algorithms for sample ascertainment and operationalization of key measures to enable the study of criminal justice contact and diversion programs among underserved populations with SMI. Aim 2: Validate and refine these algorithms through formal validation methods and in consultation with our partners. Aim 3: Test the feasibility of research using the linked dataset and algorithms by asking what types of service patterns precede incarceration of individuals with SMI and how these patterns differ across geographic and demographic subgroups, and by conducting a pilot evaluation of alternative crisis response interventions: who receives them, what their service patterns look like before and after the crisis service, how this differs between clients who receive a new mental hea...