An Ex Post Facto Evaluation Framework for Place-Based Police Interventions

Background: A small but growing body of research evidence suggests that place-based police interventions generate significant crime control gains. While place-based policing strategies have been adopted by a majority of U.S. police departments, very few agencies make a priori commitments to rigorous evaluations. Objective: Recent methodological developments were applied to conduct a rigorous ex post facto evaluation of the Boston Police Department’s Safe Street Team (SST) hot spots policing program. Research Design: A nonrandomized quasi-experimental design was used to evaluate the violent crime control benefits of the SST program at treated street segments and intersections relative to untreated street segments and intersections. Propensity score matching techniques were used to identify comparison places in Boston. Growth curve regression models were used to analyze violent crime trends at treatment places relative to control places. Units of Analysis: Using computerized mapping and database software, a micro-level place database of violent index crimes at all street segments and intersections in Boston was created. Measures: Yearly counts of violent index crimes between 2000 and 2009 at the treatment and comparison street segments and intersections served as the key outcome measure. Results: The SST program was associated with a statistically significant reduction in violent index crimes at the treatment places relative to the comparison places without displacing crime into proximate areas. Conclusions: To overcome the challenges of evaluation in real-world settings, evaluators need to continuously develop innovative approaches that take advantage of new theoretical and methodological approaches.