Koper, C., Taylor, B. G., & Woods, D. (2013). A Randomized Test of Initial and Residual Deterrence from Directed Patrols and Use of License Plate Readers at Crime Hot Spots. Journal of Experimental Criminology, 9(2), 213-244.
See also: Taylor, B. G., Koper, C., & Woods, D. (2012). Combating Vehicle Theft in Arizona: A Randomized Experiment with License Plate Recognition Technology. Criminal Justice Review, 37(1), 24-50.
Location in the Matrix; Methodological Rigor; Outcome:
Micro places, Focused, Proactive; Very Rigorous; Mixed findings
What police practice or strategy was examined?
This study examines use of license plate readers (LPRs) across a group of assigned routes (hot spots) consisting of high-risk roadway segments averaging a half-mile in length. A four-officer squad conducted short daily operations (about 1 hour) to detect stolen and other vehicles of interest at randomly selected hot spot road segments at varying times of day. The general strategy was to first “sweep” the location, checking parking lots and side streets, and then conduct fixed surveillance for the remainder of the hour, with officers positioned along different sides and parts of the route. This was done at each hot spot for eight days spread over two weeks.
How was the intervention evaluated?
Hot spots routes were randomly assigned to one of three conditions: extra patrol by the vehicle theft unit using the LPRs (the LPR condition), extra patrol and license plate checks by the vehicle theft unit but without using the LPRs (the “manual check,” non-LPR condition), and normal patrol without visits by the vehicle theft unit (the control condition). The authors examined the impact of these operations on violent, property, drug, disorder, and auto theft offenses as measured by calls for service.
What were the key findings?
Some crime types declined significantly during the weeks following patrols by the auto theft unit, suggesting residual deterrence effects. Specifically, drug calls declined 49% in the LPR routes, auto theft calls declined 75% in the manual check routes, and person crimes declined 46% in the manual check routes. Subsequent testing revealed that the reductions in auto theft and person crimes in the manual check locations did not last beyond the first 2 post-intervention weeks. In contrast, the decline in drug crimes in the LPR locations lasted for several weeks.
What were the implications for law enforcement?
Short-term patrol operations at hot spots can produce deterrent effects that reduce crime for a few weeks beyond the operations. Effects on crime can vary (in terms of length and crime types prevented) based on officers’ use of technology and how they patrol the locations. Use of LPRs in particular may help to reduce certain types of offenses at hot spots, and rotation of short-term LPR operations across hot spots may be an effective way for police agencies to employ small numbers of LPR devices. Additionally, this research suggests that police can improve their effectiveness in preventing crime at hot spots through frequent rotation of short-term directed patrols across targets.
Where can I find more information about this intervention, similar types of intervention, or related studies?