Deterrent effects of police raids on crack houses: A randomized,controlled experiment

We tested the block-level deterrent effects on crime of uniformed police raids of crack houses. Court-authorized raids were legally possible on 207 blocks with at least five calls for police service in the preceding 30 days. Raids were assigned randomly to 104 locations and were conducted at 98 of those sites; the other 109 were left alone. Experimental blocks, in relation to controls, showed reductions in both calls for service and offense reports, but effects were quite small and decayed in two weeks. Raids in which arrests were made (23 of 104 assigned) had no consistently different impact from raids in which no arrests were made. Raids had more effect on calls for service in the winter than in the spring, but we found little seasonal or period difference in effects of raids on offense reports. Alternative police methods may be far more cost-effective than raids in “harm reduction” for crack houses.