Sweet Spots of Residual Deterrence: A Randomized Crossover Experiment in Minimalist Police Patrol

Abstract

In this article, we examine how communities can maximize deterrence of crime while minimizing cost and police intrusion on public life. Using 3,720 hot spot-days, we show that the “sweet spot” duration of police absence, to maximize the residual deterrence of crime, was a full four days after the last day of targeting police patrol at each hot spot. Over a 248-day period, we randomly reshuffled 15 separate hot spots daily into either treatment (targeted police patrols) or control (no targeted patrols) for that day, so that all locations repeatedly switched between randomly assigned groups. This repeated crossover design (Cochrane & Cox, 1957; Fienberg et al., 1980) included random periods of up to 20 consecutive days in which individual hot spots remained in the control condition, allowing us to measure how soon, and by what trajectory, the residual deterrent effect of targeted patrolling wore off. After four days without patrolling, there was a sudden termination of residual deterrence, marked by a 66% rise in offense frequency, and a 395% spike in our index of crime harm (House & Neyroud 2018), compared to the treatment condition. It may be possible to deploy less, not more policing and still maximize deterrent effects.

Policing Directions: A Systematic Review on the Effectiveness of Quantitative Police Presence

“…All eligible studies implemented quantitative research designs. About three quarters of the selected studies implemented experimental research designs (n = 36), of which 13 conducted randomized controlled trials (e.g., Sherman et al 1995b, Sherman et al 1995a, Ratcliffe et al 2011, Taylor et al 2011 2014, Barnes et al 2020). On average police presence was monitored for approximately 350 days (SD ~ 483 days).…”

“…This can be well linked to the extension of the Koper curve (Koper 1995) and residual deterrence. Residual deterrence describes the effects of police presence, e.g., reduction in crime, persist for a certain amount of time even after officers left the place (Stephensen 2017, Williams and Coupe 2017, Barnes et al 2020. Initial deterrence decay deals with the duration of reduction effects and is interested in how fast deterrent effects decay (Sisiopiku and Patel 1999, Sorg et al 2013, Novak et al 2016.…”

“…The lower the ping 12 , the more precise the tracked geoinformation. Barnes et al (2020) have been able to track police activity with a ping of nine seconds using smartphones as the tracking device.…”

“…The level of police can be determined by measuring the number of officers per shift (see, Thaler 1977, Esbensen and Taylor 1984, Bowers and Hirsch 1987, Fitterer et al 2017, the shift length of officers in the target areas (e.g., Armour 1986, Weisburd et al 2011, Sorg et al 2013 or by the number of minutes spent or visits conducted by police forces (e.g., Ariel et al 2016, Ariel et al 2019, Schaefer et al 2019, Barnes et al 2020. The level of police presence is dependent on tracking precision.…”

Targeting Knife-Enabled Homicides for Preventive Policing: A Stratified Resource Allocation Model

“…Ariel et al (2020) reported that in a randomized trial in the London Underground, 15-min patrols on over 50 randomly selected hot spot platforms 4 days a week reduced crime across 7 days per week, compared with having no regular patrols on some 50 other equally "hot" high-crime frequency platforms. Most recently, Barnes et al (2020) have reported that the effects of one randomly assigned 15-min visit produced residual deterrent effects lasting for up to 4 days of no further patrols.…”