Sherman, L. & Weisburd, D. (1995). General deterrent effects of police patrol in crime “hot spots”: a randomized, controlled trial. Justice Quarterly, 12(4), 625-648.
Location in the Matrix; Methodological Rigor; Outcome:
Micro places, General, Proactive; Very Rigorous; Effective
What police practice or strategy was examined?
Recognizing that many criminologists questioned the effectiveness of uniformed police patrols in producing measurable crime differences following the Kansas City preventive patrol experiment (see Kelling et al., 1974), the authors conducted a 1-year randomized trial in Minneapolis to assess the effect of increases in police patrols at crime hot spots. Crime hot spots were defined as small clusters of addresses with frequent crime calls for police service. The final sample consisted of 110 hot spots where crime calls were concentrated between 7:00 pm and 3:00 am.
How was the intervention evaluated?
Selection of hot spots for the experiment began with an examination of dispatched calls for police service citywide to identify address clusters with 20 or more “hard calls” (i.e. serious offenses) and substantial “soft calls” (i.e. disorder offenses). 110 hot spots were ultimately selected for this study and randomly assigned to either the experimental or control group. For the 55 hot spots assigned to the experimental group, officers increased patrol presence to a target duration of 3 hours per day. Patrol logs and independent observation of the targeted hot spots were used to validate the duration of patrol presence per day in each hot spot. The impact of the increased patrol presence was measured by citizen calls concerning crime and independent observations of crime and disorder at the selected hot spots.
What were the key findings?
Findings revealed reductions in total crime calls that ranged from 6 to 13 percent with a more significant reduction in disorder at high crime hot spots. Observed disorder wwas only half as prevalent in experimental compared to control hot spots. An analysis of 13 specific types of disorder for the entire year shows that the greatest effects were on the categories of person down (on the ground), drug activity, vandalism, solicitation for prostitution, and assault. The findings support a place-specific “micro-deterrence” occurred in the hot spots which received additional patrols.
What were the implications for law enforcement?
The authors suggest that substantial increases in police patrol can modestly reduce crime and generate more impressive reductions in disorder at high-crime micro locations.
Where can I find more information about this intervention, similar types of intervention, or related studies?