This study evaluates exposure to California's Armed and Prohibited Persons System (APPS) and risk of future violence and other important outcome events among individuals who legally purchased firearms in the past but have since become prohibited from owning them. The main hypothesis is that APPS will be associated with a significant reduction in risk for future violence among individuals who are directly affected.

Violence remains an important public safety and public health problem. Prior research has shown that denying firearm purchases by individuals who are at high risk for committing violent crimes, thereby restricting their access to firearms, is an effective violence prevention strategy. The Armed and Prohibited Persons System (APPS) is a new violence prevention initiative undertaken by the California Department of Justice (CalDOJ). APPS is used by law enforcement to systematically identify persons who, having legally purchased firearms in the past, have become prohibited persons in the present-usually as the result of a criminal conviction. Such individuals are at increased risk for future violence.

APPS uses existing data to identify firearm owners among persons who have become prohibited from owning or possessing firearms under California or federal law. CalDOJ then uses this information to contact and attempt recovery of firearms in the possession of prohibited individuals.

This controlled prospective longitudinal evaluation of APPS relies principally on data collected by CalDOJ in the course of APPS operations or on data in the public domain, such as community characteristics published by the U.S. Census Bureau.

To maximize fairness during the implementation of APPS, approximately 1,000 California communities will be stratified by region, population, and violent crime rate and randomized into two groups that will be exposed to APPS at different times during the study period. Hierarchical analysis will examine outcomes for individuals clustered at the community level. The principal analysis will be on an intent to treat basis. A secondary per protocol analysis will also be conducted.

Inclusion Criteria:

• Adults with records of firearms ownership who have experienced a prohibiting event. Prohibiting events are based in Federal and California state law. Among others, they include criminal convictions for felonies and selected violent misdemeanors; emergency hospitalization for dangerousness associated with severe mental illness, as specified in statute; and status as respondent to a domestic violence restraining order.

Exclusion Criteria:

• None.