We propose to assess the influence of criminal legal systems (CLS) on the use of harm reduction services (HRS) and overdose mortality among people who use drugs (PWUD). To accomplish this, we build off Aim 1 and Aim 2 of the parent grant (R01DA057613). Like many states and municipalities across the nation, San Francisco (SF) has confronted the rise in overdose deaths by increasing police enforcement of drugs, including interdiction efforts with drugs being seized by police. However, the criminalization of drug use may pose significant barriers to the use and success of HRS and can exacerbate the risk of overdose. This can occur directly through CLS involvement but also indirectly through police efforts to disrupt unregulated drug markets. Additionally, fear of police, particularly for those under CLS supervision, may deter people from traveling to and from HRS sites. We have recently demonstrated the indirect influence of CLS on overdose in what we describe as the “Drug Bust Paradox,” which shows that police efforts to disrupt drug markets in Indianapolis was associated with significant increases in fatal overdose. We propose to test both the direct and indirect influence of CLS on the use of HRS and on overdose among PWUD in SF. For direct CLS involvement we will examine the large sample (N>1,200) of survey data collected from PWUD in the parent R01 project in SF. Along with geospatial measures of where people use drugs, the number of suppliers they buy drugs from, and detailed use of all HRS, these data also include metrics of CLS involvement that were developed as part of NIDA’s Harm Reduction Research Network (HRRN) data harmonization initiative. The investigative team has leveraged existing collaborations with the SF Police Department and the Department of Public Health to acquire crime and overdose mortality data to replicate, improve, and further test the indirect effect of CLS efforts to disrupt unregulated drug markets on overdose. We propose: Aim 1: Assess direct CLS involvement on the use of HRS. Using the PWUD Survey Data from the parent project, we will examine whether the CLS metrics developed by the HRRN are associated with lower use of HRS. Aim 2: Assess indirect CLS influence on drug supply disruptions. The PWUD Survey Data from the parent grant includes geospatial information on where people use drugs and from how many people they bought drugs. Using the administrative data, we will assess whether drug seizures are associated with PWUD needing to access drugs from more suppliers. Aim 3: Assess protective factors of harm reduction services in the association of drug supply disruption with overdose mortality. Using point-level information on drug seizures, we will use a contagion modeling approach to estimate whether CLS efforts to disrupt the unregulated drug supply affects the spread of overdose mortality events while adjusting for community-level factors, including distance to HRS. This administrative supplement will fund plann...