THE EFFECTS OF DIRECTED PATROL AND SELF‐INITIATED ENFORCEMENT ON FIREARM VIOLENCE: A RANDOMIZED CONTROLLED STUDY OF HOT SPOT POLICING

• Published date: 01 August 2014
• Author: EMILY BLACKBURN,RICHARD ROSENFELD,MICHAEL J. DECKARD
• Date: 01 August 2014
• DOI: http://doi.org/10.1111/1745-9125.12043

THE EFFECTS OF DIRECTED PATROL AND

SELF-INITIATED ENFORCEMENT ON FIREARM

VIOLENCE: A RANDOMIZED CONTROLLED STUDY

OF HOT SPOT POLICING∗

RICHARD ROSENFELD,1MICHAEL J. DECKARD,1

and EMILY BLACKBURN2

1University of Missouri—St. Louis

2St. Louis Metropolitan Police Department

KEYWORDS: hot spots, enforcement tactics, crime reduction

Targeted policing has proven effective in reducing serious crime in areas where it

is highly concentrated, but the enforcement mechanisms responsible for the success

of so-called hot spots strategies remain poorly understood. This study evaluates the

effects of a 9-month randomized controlled hot spots field experiment on firearm as-

saults and robberies in St. Louis, Missouri. Thirty-two firearm violence hot spots were

randomly allocated to two treatment conditions and a control condition. Directed pa-

trols were increased in both treatment conditions, whereas the experimental protocol

limited other enforcement activity in one of the treatment conditions and increased it

in the other. The results from difference-in-difference regression analyses indicate that

the intervention substantially reduced the incidence of nondomestic firearm assaults,

with no evident crime displacement to surrounding areas, to times when the interven-

tion was not active, or to nonfirearm assaults. By contrast, we find no effects of the

intervention on firearm robberies. Less definitive results suggest that the certainty of

arrests and occupied vehicle checks account for the treatment effects on nondomestic

firearm assaults.

Place-based or “hot spots” policing is a well-researched and effective law enforcement

strategy for achieving short-run reductions in crime (National Research Council, 2004).

Most large police departments claim to use the strategy (Police Executive Research Fo-

rum, 2008) and report that they adopted computerized crime mapping primarily to fa-

cilitate hot spots enforcement (Weisburd and Lum, 2005). The St. Louis Metropolitan

Police Department (SLMPD), the focus of the current study, has linked computerized

crime mapping to hot spots enforcement, of one kind or another, for several years. In the

∗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.2014.52.issue-3/issuetoc.

This study was supported by a grant from the National Institute of Justice (2012-IJ-CX-0042).

The views expressed are the authors’ and do not necessarily reflect those of the National In-

stitute of Justice. Direct correspondence to Richard Rosenfeld, Department of Criminology &

Criminal Justice, University of Missouri—St. Louis, 537 Lucas Hall, St. Louis, MO 63121 (e-mail:

richard rosenfeld@umsl.edu).

Correction added on 11 July 2014 after original publication: the acknowledgment has been

amended.

C2014 American Society of Criminology doi: 10.1111/1745-9125.12043

CRIMINOLOGY Volume 52 Number 3 428–449 2014 428

THE EFFECTS OF DIRECTED PATROL 429

spring of 2012, the SLMPD implemented a 9-month randomized controlled field exper-

iment to evaluate the impact of hot spots enforcement on firearm violence. The current

study reports the results of the experiment.

This study has three major objectives:

1. To analyze the effects of the experimental intervention on firearm violence hot

spots in the city

2. To identify specific enforcement tactics that may have been responsible for the

intervention effects

3. To investigate three forms of possible crime displacement—spatial and temporal

displacement and displacement to other crimes—resulting from the intervention

The study’s main contribution is to add to the growing body of experimental research on

hot spots policing by addressing the question of what the police do, or should do, to reduce

crime in hot spots. A second important contribution is to broaden the assessment of crime

displacement beyond the issue of spatial displacement that has dominated prior research.

Temporal and offense-type displacement have been proposed as theoretically plausible

consequences of place-based policing strategies (see Barr and Pease, 1990) but have not

been included in prior evaluations of hot spots policing experiments. Finally, we devote

significant attention to implementation issues and fidelity to experimental procedures,

both because such revelations are helpful in interpreting the study’s results and because

they may assist other researchers in addressing similar challenges.

BACKGROUND

Place-based targeted policing is now a common enforcement strategy in urban police

departments. How extensively the practice is used and the degree to which it has displaced

the “standard model” of random beat patrol and rapid response to calls for service remain

uncertain (Telep and Weisburd, 2011). But evidence for the effectiveness of the strategy,

much of it derived from randomized or quasi-randomized experimental designs, is ro-

bust. Systematic research reviews have revealed that most place-based policing strategies

yield small but significant reductions in crime that often diffuse into areas surrounding

targeted hot spots (Braga, 2005, 2007; Braga, Papachristos, and Hureau, 2012). Upend-

ing a longstanding belief among the police, the accumulated evidence indicates that hot

spots enforcement rarely displaces crime to surrounding areas (Eck, 1993; Green, 1995;

Guerette and Bowers, 2009; Ratcliffe and Breen, 2011; Weisburd et al., 2006).

One often overlooked consideration in prior research has been the amount of time po-

lice spend patrolling hot spots. Most studies have not specified the optimal duration of hot

spots patrols. Many hot spots interventions have erred on the side of caution by assigning

officers to hot spots for longer than may be necessary to maximize patrol effectiveness.

Koper (1995) found, however, that the optimal duration of targeted patrol in hot spots

is between 10 and 15 minutes. After 15 minutes, the presence of police officers yields di-

minishing returns in crime reduction, resulting in wasted police resources that could be

better used in another area. Koper (1995) also suggested that limiting the time spent pa-

trolling one area may increase the effectiveness of officers by avoiding boredom. Koper’s

(1995) results were based on patrols targeting single intersections, and it is not yet clear

whether they hold for larger areas (see Telep, Mitchell, and Weisburd, 2012, for similar

results). Nonetheless, the intervention under consideration here restricted the length of

time officers were directed to patrol hot spots.