The Philadelphia Foot Patrol Experiment: A Randomized Controlled Trial of Police Patrol Effectiveness in Violent Crime Hotspots

Originating with the Newark foot patrol experiment, research has found police foot patrols improve community perception of the police and reduce fear of crime, but are generally unable to reduce the incidence of crime. Previous tests of foot patrol have, however, suffered from statistical and measurement issues and have not fully explored potential dynamics of deterrence within micro-spatial settings. In this paper we report on the efforts of over 200 foot patrol officers during the summer of 2009 in Philadelphia. GIS analysis was the basis for a randomized controlled trial of police effectiveness across 60 violent crime hotspots. Results identified a significant reduction in the level of treatment area violent crime after 12 weeks. A linear regression model with separate slopes fitted for treatment and control groups clarified the relationship further. Even after accounting for natural regression to the mean, target areas in the top 40% on pre-treatment violent crime counts had significantly less violent crime during the operational period. Target areas outperformed the control sites by 23 percent, resulting in a total net effect (once displacement was considered) of 53 violent crimes prevented. The results suggest that targeted foot patrols in violent crime hotspots can significantly reduce violent crime levels as long as a threshold level of violence exists initially. The findings contribute to a growing body of evidence on the contribution of hotspots and place-based policing to the reduction of crime, and especially violent crime, a significant public health threat in the United States. We suggest that intensive foot patrol efforts in violent hotspots may achieve deterrence at a micro-spatial level, primarily by increasing the certainty of disruption, apprehension and arrest. The theoretical and practical implications for violence reduction are discussed.