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Micro Places – Koper et al. (2022)

Study Reference:

Koper, C. S., Lum, C., Wu, X., Johnson, W., & Stoltz, M. (2022). Do license plate readers enhance the initial and residual deterrent effects of police patrol? A quasi-randomized test. Journal of Experimental Criminology, 18(4), 725-746.

Location in the Matrix; Methodological Rigor; Outcome:

Micro places; General; Proactive; Rigorous; Mixed effects

What police practice or strategy was examined?

This study examined the impact of hot spot patrols with license plate readers (LPRs) within a large suburban jurisdiction in the U.S. Across three districts, officer patrol cars were equipped with LPRs. Officers were assigned 1-3 hot spots and instructed to patrol these hot spots between 1 to 3 times each day, typically during day shifts (6:30 a.m. to 4:30 p.m.) and evening shifts (3:30 p.m. to 1:30 a.m.). Hot spot patrols lasted for 15-30 minutes per visit, adhering to the Koper Curve principle. The experiment spanned 4.5 months, from May 2017 to September 2017.

How was the intervention evaluated?

The research team, crime analysts, and participating officers identified 42 high-crime areas (approximately 0.1 square miles on average) across the three districts. Half of these areas were randomly assigned to receive hot spot patrols with LPR as a treatment, while the other half served as a control group and received normal hot spot patrols without LPR. To measure the initial deterrent effect of the intervention, researchers compared the occurrence of a new crime or disorder in treatment and control hot spots while a officer was physically present in that location. To measure the residual deterrent effect, researchers analyzed the time from each visit until the next occurrence of crime or disorder at treatment and control hot spots. Crime and disorder occurrences at the hot spots during officer presence and after their visits were measured based on calls for service. Finally, the authors also compared the recovery of stolen vehicles and apprehension of offenders while officers were present within treatment and control hot spots.

What were the key findings?

LPR use increased stolen vehicle recovery, however, the authors found no evidence of a crime reduction effect associated with LPR patrols in crime hot spots. Specifically, the use of LPRs did not decrease the likelihood of new calls for service while officers were present, nor did it impact the timing or severity of subsequent calls following a patrol. In addition, LPR patrols did not produce greater deterrence than non-LPR patrols in either nearby (2-3 blocks within LPR locations) or distant non-LPR locations.

What were the implications for law enforcement?

This study provides little evidence for the crime prevention effects of LPR use in general patrol. The authors suggest that the effectiveness of LPRs may depend on various factors, including how officers use LPRs in the field. They also caution that the current deployment of LPRs, mounting them on general patrol vehicles, may not be the most optimal way to prevent crime. Given the significant expenditures on LPRs and the ongoing interest in their use, the authors recommend that further studies be conducted to provide more evidence on the efficacy of LPRs, especially in higher base rates of crime and disorder and over long periods.

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