Do license plate readers enhance the initial and residual deterrent effects of police patrol? A quasi-randomized test

Abstract

To determine whether the use and display of license plate readers (LPRs) enhance the crime prevention effects of police patrol, particularly by increasing initial and residual deterrence from patrol presence. Crime hot spots in a large suburban jurisdiction were randomly assigned to receive intermittent patrols (15–30 min each) by officers with or without LPRs on their vehicles for 4.5 months. Data on 785 patrols at 33 hot spots were used to compare initial and residual outcomes of LPR and non-LPR patrols. Outcomes analyzed for each patrol visit via chi-square tests, survival analyses, and/or logistic regression included the following: the likelihood of a vehicle recovery or arrest; the likelihood of a new crime or disorder call in the location while the officer was present (measuring initial deterrence); time until a new crime or disorder call following the officer’s departure (measuring residual deterrence); and first type of call (crime or disorder) following the officer’s departure (measuring residual deterrence). LPR use increased stolen vehicle recoveries but not arrests. LPR use did not reduce the likelihood of a new call in the hot spot while an officer was present, nor did it affect the timing or seriousness of the next call following a patrol. This study provides little clear evidence for the crime prevention efficacy of using LPRs in general patrol, which is a common practice in the USA. Police and researchers should give more attention to testing the relative benefits of different LPR uses and modes of deployment.