In 2012, California's voters passed a ballot initiative that scaled back the state's “Three Strikes” sentencing law and permitted certain individuals who were serving 25‐to‐life prison terms to petition for resentencing and potentially release. Using analysis of original qualitative interview data supplemented with court administrative records, this study examines how characteristics of courtroom workgroup members; their intergroup dynamics; political, professional, and administrative considerations; and allocated resources were perceived by court officials to facilitate or impede the implementation of this reform in county courts. Availability of staff and budget was associated with a higher proportion of completed case dispositions in the first 2 years of implementation, but resources were not the only factor associated with timely case processing. Courtroom actors' seniority, experience, and professional security facilitated agreement on processes, schedules, and other details. Small, stable, close‐knit groups established routine procedures and developed expertise more quickly, but could not always avoid bottlenecks or delays. Less stable workgroups had higher rates of denial of petitions for resentencing. Positions toward Proposition 36 shaped by political, professional, or other priorities were perceived to influence some elected DAs' positions and line prosecutors' behavior, manifesting in cooperation, opposition, or mixed messages.