License plate reader (LPR) police patrols in crime hot spots: an experimental evaluation in two adjacent jurisdictions

This randomized controlled experiment tests whether license plate readers (LPR) deter crime generally, and automobile crime more specifically in crime hot spots. The limited intervention tested here reflects one current likely use of LPR at the time of this publication. We use a place-based block randomized experiment. Our subjects were 30 hot spots in two jurisdictions, 15 which were assigned to experimental conditions. The treatment involved targeted police patrols using a "sweep and sit" approach with license plate readers in these hot spots, also applying the Koper Curve timing principle. We examine effects of the intervention during and in a 30-day period post-intervention, controlling for pre-intervention levels of crime, seasonal factors, and jurisdiction. Our findings indicate that, when small numbers of LPR patrols are used in crime hot spots in the way we have tested them here, they do not seem to generate either a general or offense-specific deterrent effect. While we did not find significant findings of this intervention, a number of limitations and caveats to this study must be considered in conjunction with these findings. The authors suggest how already acquired LPRs might be used in ways that might increase their effectiveness in crime hot spots.