DOES WHAT POLICE DO AT HOT SPOTS MATTER? THE PHILADELPHIA POLICING TACTICS EXPERIMENT*

• Date: 01 February 2015
• Author: RALPH B. TAYLOR,EVAN T. SORG,NOLA M. JOYCE,ELIZABETH R. GROFF,JERRY H. RATCLIFFE,CORY P. HABERMAN
• Published date: 01 February 2015
• DOI: http://doi.org/10.1111/1745-9125.12055

DOES WHAT POLICE DO AT HOT SPOTS MATTER?

THE PHILADELPHIA POLICING TACTICS

EXPERIMENT∗

ELIZABETH R. GROFF,1JERRY H. RATCLIFFE,1

CORY P. HABERMAN,1EVAN T. SORG,1NOLA M. JOYCE,2

and RALPH B. TAYLOR1

1Center for Security and Crime Science, Department of Criminal Justice,

Temple University

2Philadelphia Police Department

KEYWORDS: hot spots, policing, certainty, offender focus

Policing tactics that are proactive, focused on small places or groups of people in

small places, and tailor specific solutions to problems using careful analysis of local

conditions seem to be effective at reducing violent crime. But which tactics are most

effective when applied at hot spots remains unknown. This article documents the design

and implementation of a randomized controlled field experiment to test three policing

tactics applied to small, high-crime places: 1) foot patrol, 2) problem-oriented policing,

and 3) offender-focused policing. A total of 81 experimental places were identified

from the highest violent crime areas in Philadelphia (27 areas were judged amenable to

each policing tactic). Within each group of 27 areas, 20 places were randomly assigned

to receive treatment and 7 places acted as controls. Offender-focused sites experienced

a 42 percent reduction in all violent crime and a 50 percent reduction in violent felonies

compared with their control places. Problem-oriented policing and foot patrol did not

significantly reduce violent crime or violent felonies. Potential explanations of these

findings are discussed in the contexts of dosage, implementation, and hot spot stability

over time.

This study adds to the evidence base by conducting a randomized, controlled field ex-

periment of three approaches to hot spots policing (foot patrol [FP], problem-oriented

policing [POP], and offender-focused [OF] policing) at 60 violent crime hot spots and 21

control hot spots. All three treatments were applied by the same police department, in

∗Additional supporting information can be found in the listing for this article in the

Wiley Online Library at http://onlinelibrary.wiley.com/doi/10.1111/crim.2015.53.issue-1/issuetoc.

Preliminary results from the Philadelphia Smart Policing Experiment were presented at the 2011

American Society of Criminology’s annual meeting in Washington, DC, and at the 2012 Academy

of Criminal Justice Sciences annual meeting in New York City. The authors would like to thank

Philadelphia Police Commissioner Charles Ramsey for his continued support for research and

Deputy Commissioners Richard Ross, Kevin Bethel, and Tommy Wright as well as project ana-

lyst Anthony D’Abruzzo, Sgt. Sharon Jann, and the PPD2020 team for their extensive hard work

to make this study a reality. Direct correspondence to Elizabeth R. Groff, Center for Security and

Crime Science, Department of Criminal Justice, Temple University, Gladfelter Hall, 5th floor, 1115

Polett Walk, Philadelphia, PA 19122 (e-mail: groff@temple.edu).

C2014 American Society of Criminology doi: 10.1111/1745-9125.12055

CRIMINOLOGY Volume 53 Number 1 23–53 2015 23

24 GROFF ET AL.

the same city, over approximately the same time period, providing greater consistency

than systematic reviews of studies implemented across different cities and types of crime

problems.

Advances in data availability and information systems have enabled researchers and

police practitioners to examine spatial crime patterns at progressively smaller spatial units

(Eck and Weisburd, 1995; Sherman, 1997). Using these tools, researchers have demon-

strated that crime is concentrated in particular microlevel places, such as street segments

(Weisburd et al., 2004), intersections (Taniguchi, Ratcliffe, and Taylor, 2011), and ad-

dresses (Pierce, Spaar, and Briggs, 1986; Sherman, Gartin, and Buerger, 1989), and that

crime levels often vary from street to street (Groff, Weisburd, and Yang, 2010; Weis-

burd, Groff, Yang, 2012). The concentrations of crime at particular places are termed

“hot spots” (Eck et al., 2005).

This development has spurred an evolution in policing from random patrol (Weisburd

and Eck, 2004) to focusing police resources on high-crime places (Sherman, 1997; Sher-

man and Weisburd, 1995). Focusing resources on small, high-crime places has become

widely known as “hot spots policing” (Braga, 2001; Weisburd and Braga, 2003). As Braga

(2008: 7) noted, “[t]he appeal of focusing limited resources on a small number of high-

activity crime places is straightforward. If we can prevent crime at hot spot locations, then

we might be able to reduce total crime.” Cumulative evidence suggests that concentrat-

ing police resources in small areas can reduce crime (Braga, Papachristos, and Hureau,

2012; Lum, Koper, and Telep, 2011; Sherman, 1997); however, little is known about which

policing tactics are best suited for policing small areas (Telep and Weisburd, 2011). Eval-

uations of multiple tactics using robust experimental designs are scarce (for exceptions,

see Braga and Bond, 2008; Taylor, Koper, and Woods, 2011).

THEORETICAL AND EVIDENTIAL BASIS FOR HOT SPOTS

POLICING

Several theories offer plausible explanations for why concentrating police efforts at

small, high-crime places would reduce crime more effectively than unfocused patrol

strategies. Deterrence theory holds that crime occurs when the perceived risk of com-

mitting a crime is lower than the perceived reward from it (Beccaria, 1963 [1764]; Ben-

tham, 1948 [1789]). Police presence is assumed to influence the risk–reward calculus of

would-be criminals by increasing the perception that being caught and punished is more

likely, and thus, the costs of committing a crime now outweigh the potential benefits. In

this way, police create an “unremitting watch” (Shearing, 1996: 74) through which arrest

risk is increased. A careful watch by police is more likely to be noticed and perceived as

a deterrent in smaller areas.

Opportunity theories (Brantingham and Brantingham, 1991 [1981], 1993; Cohen

and Felson, 1979; Felson, 1987) emphasize that the characteristics of places struc-

ture the routine activities of individuals and produce criminogenic combinations of of-

fenders, targets, and guardianship levels at certain places and times. Different polic-

ing tactics might reduce crime in different ways, for example, by increasing the level

of guardianship at places through police presence, improving informal social con-

trol, or altering perception of the built environment to change offenders’ risk–reward

calculus.