Evidence-Based Policing Matrix

Home › Evidence-Based Policing › The Matrix › Research on Micro-Places › Micro Places – Sherman & Rogan (1995)

Micro Places – Sherman & Rogan (1995)

Study Reference:

Sherman, L. W., & Rogan, D. P. (1995). Deterrent effects of police raids on crack houses: A randomized, controlled experiment. Justice Quarterly, 12(4), 755-781.

Location in the Matrix; Methodological Rigor; Outcome:

Micro places; Focused; Proactive; Very Rigorous; Mixed findings

What police practice or strategy was examined?

Between November 1991 and May 1992, the Kansas City, MO Police Department implemented a randomized controlled trial to determine the impact of raiding crack houses on block-level crime and disorder.

How was the intervention evaluated?

Court-authorized raids were legally possible on 207 blocks with at least five calls for police service in the preceding 30 days. Raids were randomly assigned to 104 locations and were conducted at 98 of those sites; the other 109 eligible locations were not raided (thus serving as a control group). The evaluators examined the effects of the raids on offense reports and calls for service on the street blocks containing the crack houses (both sides of the street, intersection to intersection). They examined total offense reports and calls for service as well as offense reports and calls for service for violent crime, property crime, and disorder. Data was collected for a thirty-day follow up period.

What were the key findings?

Blocks assigned to receive raids showed reductions in both calls for police service and offense reports relative to control blocks, but these effects were quite small (8% net reduction compared to control) and decayed in 2 weeks. The net reduction of 29 violent crimes and 35 crimes of all types is less than 0.3 crimes deterred per raid. Raids in which arrests were made had no consistently different impact from raids in which no arrests were made. Raids had more effect on calls for police service in the winter than in the spring, but little seasonal or period differences in effects on offense reports were observed.

What were the implications for law enforcement?

Raids on crack houses produce small and brief reduction in crime and calls for service on surrounding blocks. However, the authors suggest that alternative police methods may be more cost-effective than raids in reducing harm from crack houses.

Where can I find more information about this intervention, similar types of intervention, or related studies?