Traffic Enforcement Through the Lens of Race: A Sequential Analysis of Post-Stop Outcomes in San Diego, California
| DOI | 10.1177/0887403417740188 |
| Published date | 01 July 2018 |
| Author | Joshua Chanin,Dana Nurge,Megan Welsh |
| Date | 01 July 2018 |
| Subject Matter | Articles |
research-article2018
Article
Criminal Justice Policy Review
2018, Vol. 29(6-7) 561 –583
Traffic Enforcement
© The Author(s) 2018
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https://doi.org/10.1177/0887403417740188
DOI: 10.1177/0887403417740188
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A Sequential Analysis of
Post-Stop Outcomes in
San Diego, California
Joshua Chanin1, Megan Welsh1, and Dana Nurge1
Abstract
Research has shown that Black and Hispanic drivers are subject to disproportionate
stop and post-stop outcomes compared with White drivers. Yet scholars’
understanding of how and why such disparities persist remains underdeveloped. To
address this shortcoming, this article applies a sequential approach to the analysis
of traffic stop data generated by San Diego Police Department officers in 2014 and
2015. Results show that despite being subject to higher rates of discretionary and
nondiscretionary searches, Black drivers were less likely to be found with contraband
than matched Whites and were more than twice as likely to be subjected to a field
interview where no citation is issued or arrest made. Black drivers were also more
likely to face any type of search, as well as high-discretion consent searches, that end
in neither citation nor arrest. The article concludes with a discussion of the findings
and a series of recommendations.
Keywords
racial profiling, police decision-making, police discretion, race
Introduction
The notion of “Driving While Black” became part of the American lexicon not simply
because of J. Lamberth’s (1998) catchy phrase, the results of his 1994 analysis of stop
patterns on the New Jersey Turnpike (J. C. Lamberth, 1996), or the subsequent federal
1San Diego State University, San Diego, CA, USA
Corresponding Author:
Joshua Chanin, School of Public Affairs, San Diego State University, 5500 Campanile Drive, San Diego,
CA 92182-4505, USA.
Email: jchanin@mail.sdsu.edu
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Criminal Justice Policy Review 29(6-7)
investigation of New Jersey State police traffic enforcement practices (U.S. v. New
Jersey, 1999). The idea also endures because dozens of similar studies published since
then have echoed his original finding (e.g., Antonovics & Knight, 2009; Lundman &
Kaufman, 2003; M. R. Smith & Petrocelli, 2001). In short, the field has produced a
large body of research showing that Black and Hispanic drivers are subject to dispro-
portionate stop-related outcomes compared with White drivers. These findings extend
to the decision to initiate a search (Fallik & Novak, 2012; Persico & Todd, 2008), the
issuance of a citation (Regoeczi & Kent, 2014), and the execution of an arrest (Kochel,
Wilson, & Mastrofski, 2011), among various other outcomes.
Yet despite the abundance of scholarship on this issue, much remains unknown
about how and why such disparities occur. One avenue in need of further investigation
is the connections between discrete decision points during police–citizen interactions.
For traffic stops in particular, researchers have noted the need for further investigation
into how the sequence of post-stop interactions might be shaped by driver race/ethnic-
ity (Engel & Calnon, 2004; Rosenfeld, Rojek, & Decker, 2011; Weisel, 2012). A
clearer picture of how police officer decision-making processes result in race-based
disparities can provide a greater understanding of how officers exercise discretion and
may point to ways in which these disparities might be addressed.
This article, which considers the effects of driver race on traffic enforcement in San
Diego, California, contributes such an examination. The study begins with an analysis of
several key post-stop outcomes, including the issuance of a citation or a warning, the
conduct of a field interview, the initiation of a search and the corresponding discovery of
contraband, and the arrest. From there, we examine the connection between decision
points in an effort to identify patterns in officer behavior, and with the aim of contribut-
ing a deeper understanding of the relationship between driver race and police decision-
making. We begin with a review of relevant literature on each of these four potential
outcomes, as well as a brief description of the San Diego context. Next, we describe data
and statistical method, followed by a discussion of the results. The article concludes with
an analysis of the findings and a series of policy and research recommendations.
Literature Review
Traffic stops are one of the most frequent forms of police–citizen encounters, and for
many citizens, traffic stops may be the only contact they have with the police (Eith &
Durose, 2011; Epp, Maynard-Moody, & Haider-Markel, 2014; Gilliard-Matthews,
Kowalski, & Lundman, 2008; Langton & Durose, 2013; Skolnick, 1966). Though con-
strained to a degree by federal, state, and local laws, as well as by organizational rules
and norms, individual officers have considerable authority over not only which drivers
are stopped, but who is searched, when a field interview may be conducted, when an
arrest may be initiated, and when a citation may be issued. With the application of dis-
cretionary practices comes the possibility of disparities based on the race of drivers.
Over the past two decades, scholars have examined traffic stop data from dozens of
American law enforcement agencies, as well as survey data on public–police contacts,
in an effort to assess the extent to which driver race affects the decision to stop, as well
Chanin et al.
563
as a range of post-stop outcomes. In the review that follows, we largely limit our dis-
cussion of trends in the research to disparities found in the treatment of Black drivers
as compared with White drivers as foreground to our analyses. We do so while noting
that although the magnitude of disparity is consistently largest between these two
racial groups, disparate treatment has also been found to be experienced by Hispanic
drivers (Engel, Cherkauskas, Smith, Lytle, & Moore, 2009; Fallik & Novak, 2012;
Persico & Todd, 2008; Urban Institute, 2016), and that research on Asian/Pacific
Islander, Native American, and Middle Eastern (Rice & Parkin, 2010) drivers, among
other groups, is important and noticeably lacking.1
Decision to Stop
Roughly 12% of drivers nationwide experience a police-initiated traffic stop per year
(Lundman & Kaufman, 2003), and among drivers of color, the percentage is esti-
mated to be double that (Engel & Calnon, 2004; Epp et al., 2014). Statistical assess-
ments of whether driver race is predictive of the likelihood of being stopped indeed
often suggest that there are racial disparities in who police officers stop (Gaines,
2006; Horrace & Rohlin, 2016; Ritter, 2013; Ross, Fazzalaro, Barone, & Kalinowski,
2016; Taniguchi, Hendrix, Aagaard, Strom, Levin-Rector, & Zimmer, 2013; though
for conflicting findings, see Grogger & Ridgeway, 2006; Ridgeway, 2009; Worden,
McLean, & Wheeler, 2012). However, the analysis of the effect of driver race on the
likelihood of being stopped is complicated by various measurement difficulties,
including the “denominator problem” (Schafer, Carter, Katz-Bannister, & Wells,
2006, pp. 186-187; Walker, 2001) of a lack of an accurate benchmark for a jurisdic-
tion’s driving population (Engel, Frank, Klahm, & Tillyer, 2006), the expensive
nature of observational studies (Engel & Calnon, 2004), and the challenge of control-
ling for factors such as ambient light at night (Grogger & Ridgeway, 2006; Horrace
& Rohlin, 2016; Authors’ Own).
Post-Stop Outcomes
A somewhat more straightforward way of assessing the potential presence of racial
bias is to look at a range of post-stop outcomes, which allows researchers to more eas-
ily isolate and examine the effects of driver race on these police actions. Here, we
review the extant knowledge on the effect of driver race on the various post-stop
searches which police may conduct; contraband discovery, field interviews, and the
issuance of citations or tickets.
Search. Each type of search that an officer may conduct during a traffic stop involves
varying levels of discretion (Fallik & Novak, 2012). It is important to note that the
ability to disaggregate police data by search type is dependent upon data quality; in
some jurisdictions, researchers have been unable to make distinctions by search type,
as some police departments do not differentiate by search type in their data collection
systems (see, for example, Parker, Lane, & Alpert, 2010; Renauer, 2012). Here, we
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Criminal Justice Policy Review 29(6-7)
describe the extent to which researchers have been able to ascertain whether racial
disparities arise by search type as well as across all searches.
Mandatory searches, such as those conducted incident to an arrest or upon vehicle
impound, are considered to be “low discretion” searches, as they are often required
under department policy (Alpert, Dunham, & Smith, 2008; Higgins, Jennings, Jordan,
& Gabbidon, 2011; Schafer, Carter, Katz-Bannister, & Wells, 2006). Officers are
within their legal rights to conduct a search when an arrest is made (Arizona v. Gant,
2009; U.S. v. Robinson, 1973) and when a vehicle is impounded (South Dakota v.
Opperman, 1976). Because most such searches occur automatically—and typically
after the arrest (Rosenfeld et al., 2011)—any race-based disparities that emerge reveal
less about officer behavior than...
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