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DOI: 10.1111/1745-9133.12412
RESEARCH ARTICLE
RESEARCH ON BODY-WORN CAMERAS
Research on body-worn cameras
What we know, what we need to know
Cynthia Lum Megan Stoltz Christopher S. Koper J. Amber Scherer
George Mason University
Correspondence
Cynthia Lum, Department of Criminology,
Law and Society,George Mason University,
4400 University Drive, MS 6D12, Fairfax,
VA22030.
Email: clum@gmu.edu
Research Summary: In this article, we provide the most
comprehensive narrative review to date of the research
evidence base for body-worn cameras (BWCs). Seventy
empirical studies of BWCs were examined covering the
impact of cameras on officer behavior, officer perceptions,
citizen behavior, citizen perceptions, police investigations,
and police organizations. Although officers and citizens
are generally supportive of BWC use, BWCs have not
had statistically significant or consistent effects on most
measures of officer and citizen behavior or citizens’ views
of police. Expectations and concerns surrounding BWCs
among police leaders and citizens have not yet been
realized by and large in the ways anticipated by each.
Additionally, despite the large growth in BWC research,
there continues to be a lacuna of knowledge on the impact
that BWCs have on police organizations and police–citizen
relationships more generally.
Policy Implications: Regardless of the evidence-base,
BWCs have already rapidly diffused into law enforcement,
and many agencies will continue to adopt them. Policy
implications from available evidence are not clear-cut, but
most likely BWCs will not be an easy panacea for improv-
ing police performance, accountability, and relationships
with citizens. To maximize the positive impacts of BWCs,
police and researchers will need to give more attention to
the ways and contexts (organizational and community) in
Criminology & Public Policy. 2019;1–26. wileyonlinelibrary.com/journal/capp © 2019 American Society of Criminology 1
2LUM ET AL.
which BWCs are most beneficial or harmful. They will also
need to address how BWCs can be used in police training,
management, and internal investigations to achieve more
fundamental organizational changes with the long-term
potential to improve police performance, accountability,
and legitimacy in the community.
KEYWORDS
body-worn cameras, evidence-based, law enforcement, policing, review,
technology
1INTRODUCTION
Body-worn cameras (BWCs) are one of the most rapidly diffusing technologies in policing today,
costing agencies and their municipalities millions of dollars. In 2013, the Bureau of Justice Statistics
Law Enforcement Management and Administrative Statistics (LEMAS) survey (Bureau of Justice
Statistics, 2013) revealed that almost a third of agencies had “utilized video cameras on patrol
officers.” The Major Cities Chiefs and Major County Sheriffs associations surveyed their members
in 2015 and found that 19% had adopted BWCs, whereas an additional 77% stated that they planned
to adopt them in the near future (Lafayette Group, 2015). The International Association of Chiefs of
Police (IACP, 2014) has already developed model policies for this technology, signaling its widespread
use and importance in law enforcement. At the time of this publication, the Bureau of Justice Statistics
had just released its first body-worn camera supplement to the LEMAS, which reports that as of 2016,
60% of local police departments and 49% of sheriffs' offices had fully deployed their BWCs (Hyland,
2018). It would likely not be an exaggeration to estimate that the number of U.S. law enforcement
agencies today (end of 2018) that currently use BWCs has more than likely doubled since 2013.
The rapid adoption of BWCs in the United States has been propelled by highly publicized events
in this decade involving (often) White police officers killing (often) unarmed Black individuals.
Arguably the first pivotal event of this era did not involve a police officer but an armed individual
posing as a neighborhood watchman, who killed an unarmed Black youth—Travon Martin—in 2012.
This was followed by the shooting of Michael Brown in 2014 by a Ferguson, Missouri, police officer
and then the death of Freddie Gray in Baltimore City Police Department custody in 2015. Many of
these officer-involved shootings have made national headlines, and in some cases, they have led to
the conviction and imprisonment of officers (see Blinder's [2017] coverage of the sentencing of a
North Charleston police officer who had shot unarmed Michael Scott). Although most, if not all, of
these events were caught on citizen cell phone cameras, the idea that greater accountability for police
actions could be obtained had previous events been filmed became a prominent source of citizen
demands for BWCs (see general discussions by Braga, Sousa, Coldren, & Rodriguez, 2018; Maskaly,
Donner, Jennings, Ariel, & Sutherland, 2017; Nowacki & Willits, 2018; White, 2014).
These events were watershed moments in American policing that spurred on the rapid adoption of
BWCs. They reflect, however, long-incubating concerns in the United States about police authority
and racial minorities as well as about police–community relations. These concerns include law
enforcement's use of stop-question-and-frisk (see Gelman, Fagan, & Kiss, 2007); increases in their
use of misdemeanor arrests since the mid-1990s (see Harcourt & Ludwig, 2006; Lum & Vovak,
LUM ET AL.3
2018); the consistent incongruent perceptions of treatment between Whites and non-Whites in traffic
and pedestrian stops (see Gallup Organization, 2014; Langton & Durose, 2013); and police use of
force (see Worden, 2015), especially within Black and Hispanic communities. Many of these issues
were embodied in the report and recommendations of President Obama's Task Force on 21st Century
Policing (2015), in which the Task Force described the influence of both current and historical context
on these issues. In culmination, this context fostered enough public and political will to generate an
urgent call for BWCs in this decade. This demand was matched with a prepared supplier; technology
companies had already been developing both BWCs and other similar surveillance devices (e.g., in-car
cameras, license plate readers, and closed-circuit televisions). Connecting this supply with the demand
was the initial $20 million investment in BWCs by the U.S. Department of Justice (2015; administered
by the Bureau of Justice Assistance) followed by continued investment in BWC acquisition and
training by federal,1state, and local governments.
Because the rapid adoption of BWCs was driven by public protest, law enforcement concerns, a
historical backdrop, government funding, and the development of portable video technology, it should
not be any surprise that BWCs were quickly adopted in a low-research environment (Lum, Koper,
Merola, Scherer, & Reioux, 2015). The first review of BWCs was conducted by White (2014), who
discovered only five evaluation studies had been completed as of September 2013, even though almost
a third of U.S. agencies had already adopted BWCs. In other words, agencies had already begun rapidly
adopting BWCs without clear knowledge about whether the technology could deliver on the high
expectations of them (i.e., to increase police accountability, reduce the use of force, reduce disparity,
and improve community relationships). A low-information environment is not unusual in the world of
police technology adoption. Most technologies are not only adopted without research knowledge but
also continue to be adopted with very little growth in evaluation research about their effects. License
plate readers, for example, are a case in point (see discussion in Lum & Koper, 2017: 111–124).
The importance of scientific inquiry (and not just of technical research) about police technologies
like BWCs, however, cannot be overstated. Most importantly, if law enforcement—and ultimately,
citizens—intend to invest heavily in BWCs, then BWCs should do what we expect them to do. Unfortu-
nately, researchers have consistently found that police technology may not lead to the outcomes sought,
and often it has unintended consequences for police officers, their organizations, and citizens (Chan,
Brereton, Legosz, & Doran, 2001; Colton, 1980; Koper, Lum, Willis, Woods, & Hibdon, 2015; Lum,
Hibdon, Cave, Koper, & Merola, 2011; Lum, Koper, & Willis, 2017; Manning, 2008; Orlikowski &
Gash, 1994). The reason for this is that technology is often filtered through—and shaped by—human
factors (e.g., officers’ reactions to and uses of technology) as well as through an agency's organiza-
tional, procedural, and cultural ways (Lum et al., 2017; Manning, 2008; Orlikowski & Gash, 1994).
Without the results of rigorous research and evaluation, law enforcement leaders are left to rely on best
guesses, hunches, notions about “craft,” and “group think” about the impact of technologies like BWCs
(see discussion by Lum & Koper, 2017). Research knowledge about technologies, if minded, not only
can moderate these forces, but also it can help law enforcement agencies anticipate unintended conse-
quences, optimize their use of already acquired technologies, or decide whether to invest in a specific
technology.
Fortunately, researchers have taken a major interest in studying BWCs in the last 5 years and have
tried to keep up with its rapid adoption. For example, by November 2015, Lum et al. (2015) found that
completed studies about BWCs had grown to more than a dozen, with 30+additional studies under-
way. Most of the studies included in both White (2014) and Lum et al.’s reviews were focused on the
impact that BWCs had on officer behavior as measured by complaints and their use of force, as well as
on officer perceptions about BWCs. Maskaly et al. (2017), in a review of police and citizen outcomes
more specifically, found 21 empirical studies as of January 2017, which led them to conclude that
4LUM ET AL.
police are generally receptive to BWCs and that the cameras can exert positive effects on police behav-
ior. Our current review, which includes all empirical studies found or accepted for publication through
June 2018, consists of 70 published or publicly available studies of BWCs.2Additionally, many of
these studies are rigorous outcome evaluations, which are unusual in police technology research.
Here we review, analyze, and comment on this current state of empirical research in the context of
this significant era of policing in which we find ourselves. To be as inclusive as possible, we searched
all relevant library and research databases available3for publicly available reports and articles
(whether published by a journal, press, organization, or the authors themselves on the Internet, or in
thesis or dissertation form). We used multiple keywords (and their variants) in these searches (i.e.,
body-worn cameras, body worn video, body cameras, officer video, body cams, police, and video)
and included any study or article that included empirical analysis (whether qualitative or quantitative).
Additionally, since 2015, we have been collecting information from ongoing research projects through
criminal justice conferences and symposia, grant awards from both government and nongovernment
sources, and from colleagues in the field, which helped to identify studies that did not initially emerge
in our database search.
Our definition of “empirical research” is broad and inclusive, and it consists of any study in
which either qualitative or quantitative data were collected to study BWCs. For example, we did not
limit ourselves to only outcome evaluations of BWCs. A large proportion of BWC research is not
evaluative, but descriptive survey research that can lend important insights into perceptions of BWCs
and their use. We did exclude theoretical, hypothetical, opinion/editorial, or legal writings in which no
systematic scientific study or data collection was attempted. Because of the breadth of this research,
we emphasize that we do not present a systematic meta-analysis or meta-aggregation of BWC research
here.4The empirical research on BWCs employs a variety of methods and perspectives, and our
intention in this article is to draw out tendencies and hypotheses from this research for policy as well
as for scholarly audiences. Thus, we not only report on the findings of this evidence-base but also
highlight broader debates and discussions that are provoked by the research that law enforcement
agencies and researchers should consider.
2TRENDS OF BWC RESEARCH
In total, we found approximately 70 publicly available empirical research articles5as of June 2018 in
which research findings related to BWCs and the police were reported. We denote these articles in our
reference section with an asterisk (*). This body of research reflects, approximately, a 14-fold increase
in research since White's (2014) review, a 5-fold increase since Lum et al.’s (2015) assessment, and
more than a 3-fold increase since Maskaly et al.’s (2017) review. Furthermore, we found at least 111
substudies of various outcomes within these 70 publications. More than one third of the studies were
conducted by researchers at Arizona State University (15 of the 70 studies) or by Barak Ariel and
his colleagues (12 of the 70 studies), but the remainder were carried out by numerous researchers
from many different institutions. The BWC research also took place in diverse locations. For example,
although 52 (74%) of these studies were conducted in U.S. jurisdictions, 14 (20%) were implemented
outside of the United States, and 4 (7%) were multisite trials conducted across multiple countries. At
least a quarter of the studies were carried out in cities and towns with populations smaller than 250,000
people. Finally, the BWC research we found did not just appear in peer-reviewed journals; a third of the
studies are grant reports, unpublished manuscripts, or technical reports by law enforcement agencies.
Building on Lum et al.’s (2015) typology of BWC studies, we grouped these studies into six areas
of research shown in Figure 1 (studies may fall into multiple categories). These categories are as
LUM ET AL.5
32
32
16
16
7
8
0 5 10 15 20 25 30 35
(1) OFFICER BEHAVIORS
(2) OFFICER ATTITUDES
(3) CITIZEN BEHAVIORS
(4) CITIZEN/COMMUNITY ATTITUDES
(5) INVESTIGATIONS
(6) ORGANIZATIONAL IMP ACTS
FIGURE 1 Frequency of body-worn camera studies by general outcome studied
follows: (1) the impact of BWCs on officer behavior, (2) officer attitudes about BWCs, (3) the impact
of BWCs on citizen behavior, (4) citizen and community attitudes about BWCs, (5) the impact of
BWCs on criminal investigations, and (6) the impact of BWCs on law enforcement organizations. As
Figure 1 shows, the most common types of research on BWCs focus on how BWCs impact officer
behaviors as well as on officer attitudes and perceptions about BWCs.
Table 1 lists the more specific subcategories of topics initially presented by Lum et al. (2015: Table 2,
14–17) and each study that corresponds with that subarea. Studies are listed multiple times if mul-
tiple outcomes or aspects of BWCs were examined. Because so few studies have been conducted
on the impact of BWCs on police organizations, we collapse Lum et al.’s multiple categories in
that area into a single grouping. We now present a narrative review of this research across these
six categories.
3IMPACT OF BODY-WORN CAMERAS ON OFFICER
BEHAVIOR
One of the greatest expectations of BWCs by citizens and perhaps by police supervisors and leaders
is that BWCs can change police officer behavior, and a sizeable portion of BWC research—at least
32 studies—has been focused on officer behavior.6For example, BWCs are theorized to have a
deterrent effect on excessive use of force and unconstitutional actions by officers (see Ariel, Farrar, &
Sutherland, 2015, and Ariel et al., 2017, for extensive discussions of the application of deterrence and
self-awareness theories to BWCs). BWCs are also believed to moderate possible negative interactions
(i.e., rudeness and disrespect) that officers may have with citizens (either initiated by an officer or
citizen). Researchers in this area primarily have measured this impact by examining complaints made
against officers as well as reports of officers’ use of force.7In some studies, however, scholars have
also examined the impact that BWCs have on other types of officer behaviors such as the use of arrest
and citations, or their proactive activities.
Methodologically, the research in this area has been rigorous. In 14 studies, scholars have used
randomized controlled experiments to evaluate these effects, and in at least 10 more, they have used
strong quasi-experiments or, in one case, systematic social observations. Although many of these
studies comprise some amount of contamination, attrition, and design challenges, it is important to
emphasize that the level of believability of these findings is fairly strong.
6LUM ET AL.
TABLE 1Subareas of BWC studies with citations
1. Impact of BWCs on officer behavior
1a. Impact on officer behavior as
measured by complaints
Ariel (2016a); Ariel et al. (2015); Ariel et al. (2017); Barela (2017); Braga,
Barao, et al. (2018); Braga, Sousa, et al. (2018); Edmonton Police Service
(2015); Ellis et al. (2015); Goodall (2007); Goodison and Wilson (2017);
Grossmith et al. (2015); Headley et al. (2017); Hedberg et al. (2016);
Jennings et al. (2015); Katz et al. (2014); Mesa Police Department (2013);
Mitchell et al. (2018); Peterson et al. (2018); Sutherland et al. (2017);
Toronto Police Service (2016); White, Gaub, et al. (2018); Yokum et al.
(2017)
1b. Impact on officer behavior as
measured by use of force reports
Ariel (2016a); Ariel et al. (2015); Ariel et al. (2016a); Braga, Barao, et al.
(2018); Braga, Sousa, et al. (2018); Edmonton Police Service (2015);
Headley et al. (2017); Henstock and Ariel (2017); Jennings et al. (2015);
Jennings et al. (2017); Peterson et al. (2018); Rowe et al. (2018);
Sutherland et al. (2017); Toronto Police Service (2016); White, Gaub, et al.
(2018); Yokum et al. (2017)
1c. Impact on officer discretion
related to arrests or citations
Ariel (2016a); Braga, Sousa, et al. (2018); Goodall (2007); Grossmith et al.
(2015); Headley et al. (2017); Hedberg et al. (2016); Katz et al. (2014);
McClure et al. (2017); Peterson et al. (2018); Ready and Young (2015);
Rowe et al. (2018); Toronto Police Service (2016); Wallace et al. (2018);
Yokum et al. (2017)
1d. Impact on officer's proactive
behaviors (i.e., problem solving,
field interviews, stop and frisk,
community policing, etc.
Grossmith et al. (2015); Headley et al. (2017); Peterson et al. (2018); Ready
and Young (2015); Wallace et al. (2018); White, Todak, et al. (2018)
1e. Impact on officer-citizen
interactions using other
measures (e.g., observations)
Koen (2016); McCluskey et al. (2019); Rowe et al. (2018)
2. Officer attitudes about BWCs Edmonton Police Service (2015); Ellis et al. (2015); Fouche (2014); Gaub
et al. (2016); Gaub et al. (2018); Goetschel and Peha (2017); Goodall
(2007); Gramaglia and Phillips (2017); Grossmith et al. (2015); Guerin
et al. (2016); Headley et al. (2017); Huff et al. (2018); Hyatt et al. (2017);
Jennings et al. (2014); Jennings et al. (2015); Katz et al. (2014); Koen
(2016); Kyle and White (2017); Lawshe (2018); Makin (2016); McLean
et al. (2015); Newell and Greidanus (2017); Obasi (2017); Owens and Finn
(2018); Pelfrey and Keener (2016); Ready and Young (2015); Rowe et al.
(2018); Smykla et al. (2015); Tankebe and Ariel (2016); Toronto Police
Service (2016); White, Todak, et al. (2018); Young and Ready (2015)
3. Impact of BWCs on citizen behavior
3a. Impact on an individual's
compliance with police
Ariel et al. (2016b); Ariel et al. (2018); Barela (2017); Grossmith et al.
(2015); Headley et al. (2017); Hedberg et al. (2016); Katz et al. (2014);
McCluskey et al. (2019); Toronto Police Service (2016); White et al.
(2017); White, Gaub, et al. (2018)
3b. Impact on citizen's (victim or
witness) willingness to call the
police
Ariel (2016b); Edmonton Police Service (2015); Toronto Police Service
(2016)
3c. Impact on citizen's willingness
to cooperate in investigations
Edmonton Police Service (2015); Grossmith et al. (2015); Toronto Police
Service (2016)
3d. Impact on crime and disorder
when officer is present
(deterrence)
Ariel (2016b); Ellis et al. (2015); Goodall (2007); ODS Consulting (2011)
(Continues)
LUM ET AL.7
TABLE 1(Continued)
4. Impact of BWCs on citizen and community attitudes about police or cameras
4a. Impact on citizen satisfaction
with specific officer encounters
Goodison and Wilson (2017); McClure et al. (2017); Toronto Police Service
(2016); White et al. (2017)
4b. Impact on citizen satisfaction
with police more broadly
(confidence, legitimacy, trust)
and general support for BWCs
Crow et al. (2017); Culhane et al. (2016); Ellis et al. (2015); Goodison and
Wilson (2017); Kerrison et al. (2018); Owens and Finn (2018); Plumlee
(2018); Sousa et al. (2018); Taylor et al. (2017); Todak et al. (2018);
Toronto Police Service (2016); White et al. (2017)
4c. Impact on attitudes related to
privacy and willingness to talk
to police
Crow et al. (2017); Edmonton Police Service (2015); Grossmith et al. (2015);
Taylor et al. (2017); Toronto Police Service (2016)
4d. Impact on fear of crime and
safety
Goodall (2007); Toronto Police Service (2016); White et al. (2017)
5. Impact of BWCs on criminal
investigations, such as crime
resolution, intelligence
gathering, or court
proceedings and outcomes
Ellis et al. (2015); Goodall (2007); Merola et al. (2016)a; Morrow et al.
(2016; see also Katz et al., 2014); ODS Consulting (2011); Owens et al.
(2014); Yokum et al. (2017)
6. Impact of BWCs on police
organizations (training
systems, policies,
accountability, supervision,
management, budgets,
resources)
Adams and Mastracci (2018); Braga, Sousa, et al. (2018); Culhane et al.
(2016); Edmonton Police Service (2015); Koen (2016); Nowacki and
Willits (2018)b; Phelps et al. (2018); Toronto Police Service (2016);
aMerola et al.’s (2016) study is a national survey of prosecutor viewpoints about BWCs. It is included in this review because of its
empirical relevance to this area.
bNowacki and Willits (2018) examined organizational characteristics associated with adoption of BWCs (not the impact of BWCs on
police organizations).
3.1 Impact of BWCs on complaints
Although we discovered two early empirical studies of BWCs (Goodall, 2007; ODS Consulting,
2011), the two earliest outcome evaluations of the impact of cameras on officer behavior were the 2012
Rialto (California) Police Department experiment, carried out by then-Chief William (Tony) Farrar
in collaboration with Barak Ariel at the University of Cambridge (see initially Farrar, 2012; Farrar &
Ariel, 2013; then subsequently Ariel, Farrar, & Sutherland, 2015),8and the Mesa Police Department
(2013) quasi-experiment, analyzed by researchers at Arizona State University. Since the Rialto and
Mesa studies, evaluation research on the impact that BWCs have on officer behavior has grown. In
total, in 22 of the 32 studies in this area, scholars have used complaints against officers to measure
BWC impact on officer behavior (see Table 1:1a), and in at least 18, they have employed experimental
or quasi-experimental designs to test such effects between groups of officers, beats, or shifts with and
without BWCs. In these studies, researchers have mostly found that officers wearing BWCs receive
fewer reported complaints than do those that are not wearing the cameras (see Ariel, 2016a [for
complaints related to use of force but not to misconduct]; Ariel et al., 2017; Braga, Barao, McDevitt, &
Zimmerman, 2018; Braga, Sousa, et al., 2018; Ellis, Jenkins, & Smith, 2015; Goodall, 2007; Goodison
& Wilson, 2017; Grossmith et al., 2015; Hedberg, Katz, & Choate, 2016; Jennings, Lynch, & Fridell,
2015; Katz, Choate, Ready, & Nuño, 2014; Mesa Police Department, 2013; Peterson, Yu, La Vigne,
& Lawrence, 2018; Sutherland, Ariel, Farrar, & De Anda, 2017). The exceptions to this finding are
8LUM ET AL.
in the minority. Nonsignificant impacts of BWCs on complaints against officers were discovered by
Ariel et al. (2015); Edmonton Police Service (2015); Headley, Guerette, and Shariati (2017); Toronto
Police Service (2016, whose results were unclear); White, Gaub, and Todak (2018, although noting
a downward trend in complaints for the treatment group); and Yokum, Ravishankar, and Coppock
(2017).
The more important concern for police agencies and researchers is why reports of complaints
decline when officers wear BWCs. Perhaps the effect may be a result of a real change in officer
behavior given that they know they are being recorded (Ariel et al., 2017), leading to citizens
complaining less about them. The research findings on officer perceptions of BWCs in the next
section, however, reveal a more complex story. Officers themselves believe that BWCs reduce specific
types of complaints—frivolous, malicious, or unfounded—because citizens now realize they are being
recorded. Thus, the decline in complaints seen in experimental and quasi-experimental studies may
indicate a reporting effect or a change in citizen reporting behavior rather than an effect on officer
behavior or even on the quality of police–citizen interactions (which may remain unaffected if the
reporting hypothesis holds true). Another possibility is that officers may be informally negotiating
complaints by showing potential complainants or supervisors video footage of the encounter, which
may discourage citizens from pursuing complaints for reasons unrelated to whether the complaint is
legitimate. Goodall (2007) and Koen (2016), for example, observed these types of exchanges.
The use of complaints as a measure of officer behavior or officer–citizen interaction could itself
be problematic. Complaints are rare events relative to the large number of police–citizen interactions
that occur daily. Complaints (like use of force reports) reflect the tail end of the distribution of
police–citizen interactions. Other measurement approaches—such as systematic social observations,
ethnographies, and even analysis of BWC footage itself—may provide further clues into the wider
impacts of BWCs on everyday citizen–officer interactions. For example, McCluskey et al. (2019),
through systematic social observations of officers in the Los Angeles Police Department, asserted
that BWCs seem to have a direct impact on increasing the procedural justice experienced by citizens
from officers. Whether changes in behavior improve police–citizen interactions may be a matter of
perception, however. For example, in their ethnographic study, Rowe, Pearson, and Turner (2018)
observed exchanges between officers and citizens becoming more “constrained and scripted” and
“stilted and artificial” (p. 2018: 88).
3.2 Impact of BWCs on use of force
In addition to complaints as a measure of officer behavior, in 16 studies in this area, researchers
examined the impact of BWCs on officers’ reported uses of force (see Table 1:1b). As men-
tioned, concerns about police accountability with their use of force, especially deadly force and
among racial and ethnic minorities, was a primary impetus behind the push for police to be out-
fitted with BWCs. Like those examining complaints, many of these studies have been carried out
using rigorous evaluation methods. The findings from this area of research are more equivocal,
however.
For example, the findings from four experimental studies (Ariel et al., 2015; Braga, Sousa, et al.,
2018; Henstock & Ariel, 2017; Jennings et al., 2015) and one quasi-experimental study (Jennings,
Fridell, Lynch, Jetelina, & Reingle Gonzalez, 2017) show that officers wearing cameras use force
less than do officers not wearing cameras. Additionally, in a follow-up to the original Rialto study
conducted by Sutherland et al. (2017), the authors found sustained effects of BWCs on lowering use
of force over time. The results of another four randomized controlled trials and an additional four
quasi-experimental studies, however, show no statistically significant differences in the use of force
LUM ET AL.9
by officers wearing cameras compared with their non-BWC counterparts (Ariel, 2016a; Braga, Barao,
et al., 2018; Edmonton Police Service, 2015; Headley et al., 2017; Peterson et al., 2018; Toronto
Police Service, 2016; White, Gaub, et al., 2018; Yokum et al., 2017). The direction of the effects of
these nonsignificant findings was not consistent across studies, and the findings have been equivocal
in both U.S. and non-U.S. studies.9
Ariel et al. (2016a) recently provided one nuanced explanation to these mixed findings. They
discovered that when officers have more discretion in turning on their cameras, they tend to exhibit
greater uses of force than officers who have less discretion regarding their BWCs. In most of the
use-of-force studies reviewed earlier, researchers did not track activation and therefore it was not clear
to what extent Ariel et al.’s nuance is salient. If activation is related to use of force in these ways,
however, consistently training, reinforcing, and supervising the implementation of mandatory policies
may be needed to secure a positive effect of BWCs on reported uses of force (see generally White,
Todak, et al., 2018; see also specific discussions on activation by Headley et al., 2017, and Roy, 2014
[later reported as Young & Ready, 2018]).
In total, these study findings do not reveal a definitive conclusion that BWCs can reduce officers’
use of force. Furthermore, as with official complaints, reports of uses of excessive force are infrequent
relative to more minor forms of force regularly used (i.e., handcuffing or restraining). Agencies
also have various thresholds and accountability mechanisms for when a use-of-force report must
be written, which could lead to variations in findings across sites. As with complaints, this may
challenge whether use-of-force reports are the best measure of the impact of BWCs on police officer
behavior.
3.3 Impact of BWCs on arrest and citation behaviors
In addition to complaints and use of force, researchers have examined whether BWCs change the arrest
and citation behavior of the police. For example, the wearing of BWCs might increase the use of arrests
or citations if officers feel their discretion is limited or monitored (see discussions in Ariel et al., 2017;
Koen, 2016; Rowe et al., 2018). Fourteen studies have been aimed at examining the impact of BWCs
on officer arrest and citation behavior (see Table 1:1c). In total, the findings from these studies show no
clear pattern of outcomes related to arrests and citations. For example, Ready and Young (2015) found
that officers wearing BWCs made fewer arrests but gave more citations. Ariel (2016a) and McClure
et al. (2017) also found that BWC-wearing officers made fewer arrests. Braga, Sousa, et al. (2018) and
Katz et al. (2014), however, discovered that arrests increase for BWC-wearing officers compared with
non-BWC officers, as does the Toronto Police Service (2016). Finally, neither Grossmith et al. (2015)
nor Wallace, White, Gaub, and Todak (2018) found any significant impact from BWCs on arrests
stemming from violent crimes or calls for service, respectively. These mixed findings occur within
both randomized controlled experiments as well as quasi-experimental research. In their ethnographic
research, Rowe et al. (2018) reported officers with BWCs feeling constrained in their discretion
to not arrest, especially when there is evidence of an assault (i.e., they felt that had to carry out
the arrest).
3.4 Impact of BWCs on proactivity
Much less is known about the impact of BWCs on various types of police proactivity, which can
encompass a wide range of activities when police are not responding to citizen-initiated calls for
service. Proactivity can include activities such as problem-solving, stop-question-and-frisk, traffic
enforcement, community policing and engagement efforts, directed patrol, or the use of misdemeanor
10 LUM ET AL.
arrests to reduce disorder (National Academies of Sciences, Engineering, and Medicine [NAS], 2017).
Some of these activities are controversial (for example, the use of stop-question-and-frisk), whereas
others involve fewer enforcement actions (for example, community engagement strategies). Wallace
et al. (2018) framed this discussion of the impact of BWCs on proactivity in terms of whether BWCs
caused “de-policing” or “camera-induced passivity” of officers. Perhaps BWCs make officers more
fearful of scrutiny, which leads them to “pull back” on engaging more proactively with the public.
Because of the wide range of proactive activities, there are likely different opinions about whether the
intent (or expectation) of BWCs should be to constrain police proactivity or whether the declines in
proactivity would be considered positive or negative.
We found only six studies (three randomized experiments, two quasi-experiments, and one
multivariate analysis) in which scholars empirically spoke to this question (Table 1:1d). In total, their
results are not definitive. The findings of three studies seem to indicate that BWC-wearing officers
may initiate more field encounters and contacts overall (Headley et al., 2017; Ready & Young, 2015;
Wallace et al., 2018). Focusing specifically on stop-question-and-frisks, Ready and Young (2015)
found that officers were less likely to carry out these searches when BWCs were worn, but Grossmith
et al. (2015) found no such effect (neither Headley et al. nor Wallace et al. differentiate contacts from
stop-and-frisks). Peterson et al. (2018) found no significant impact of BWCs on the levels of traffic
stops by officers (also discovered by Headley et al., 2017). Peterson et al. also reported that for both
officers with and without cameras, “subject stops” declined over time, and they declined significantly
more for officers with cameras. White, Todak, et al. (2018) also found that BWC deployment did not
have a significant impact on officer levels of proactivity (as measured using officer-initiated calls for
service).
The authors of these studies, in the context of the broader research on proactive police activities,
emphasized an important point for researchers and law enforcement officials alike. The question
for researchers to pursue that might be operationally helpful to law enforcement is not whether
proactivity has overall increased or decreased but which specific types of proactivity have increased
or decreased (and why). As the NAS (2017) report indicated (see also reviews by Braga, Welsh, &
Schnell, 2015; Lum & Koper, 2017; Lum & Nagin, 2017), some proactive activities can be effective
in reducing crime without causing community backlash; some can be effective in improving citizen
satisfaction (although not reducing crime); and some can be ineffective and degrade police–citizen
relationships. Additionally, some types of proactivity may be controversial but also effective if
used in targeted, constitutional, and very specific ways (such as stop-question-and-frisk or focused
deterrence). An important question for researchers to tackle is how BWCs impact these different types
of proactivity, in light of what we know about the differential impacts of various types of proactive
activities.
3.5 Impact of BWCs on disparity
One of the most important questions about BWCs that has yet to be tackled by any empirical research
is whether BWCs have any impact on disparate outcomes in policing and, relatedly, whether BWCs
impact 4th Amendment compliance by officers (Lum et al., 2015). The hypothesized impacts of
BWCs in increasing the fairness and constitutionality of officer actions were significant reasons
behind the push for, and acquisition of, BWCs in law enforcement. Yet, we know nothing about these
effects beyond speculation. More generally, we do not know much about the impact that any policing
intervention (e.g., specialized training, accountability adjustments, supervisory strategies, or techno-
logical advances) has on criminal justice disparity. Such research should be a priority for policing
scholars.
LUM ET AL.11
4OFFICERS’ ATTITUDES TOWARD BODY-WORN
CAMERAS
One of the largest bodies of research on BWCs (at least 32 studies of all published or publicly available
studies) has been focused on examining officer attitudes about cameras (Table 1:2). Agencies have
been open to this type of research as leaders have been concerned about how BWCs might be perceived
(and implemented) by their officers. Research in this area has been descriptive and focused on officer
perceptions about BWCs or on their specific uses within agencies. Some of the studies have taken
place within broader experimental studies described previously, whereas others have been stand-alone
surveys conducted of sworn personnel within or across jurisdictions.
The methodological rigor of these surveys has varied, and we leave a methodological analysis of this
research area to a forthcoming systematic review (see Endnote 6). To summarize, these studies—which
most often have occurred within a single agency—have varied in terms of how representative their
samples are to the population of officers in that agency, the validity of the questions used, the issues
raised, and whether changes or variations in perceptions are measured either before or after cameras
are acquired or between officer groups. Some studies have missing information that might help to
assess the strength of the survey methodology, such as statistical testing comparing characteristics of
respondents with nonrespondents or with the agency population more generally. Sometimes response
rates have been less than 50%, whereas other scholars have used samples of convenience.
Despite methodological challenges, the findings from this body of work illuminate some themes
for law enforcement and provoke hypotheses for further testing for researchers. For example, one
consistent theme that has been reported in many of these studies is that once officers start using
cameras, they feel positive (or at least neutral) about BWCs, or they become more positive about them
over time (see, e.g., Ellis et al., 2015; Fouche, 2014; Gaub, Todak, & White, 2018; Grossmith et al.,
2015; Jennings, Fridell, & Lynch, 2014; Jennings et al., 2015; Koen, 2016; McLean, Wolfe, Chrusciel,
& Kaminski, 2015; Smykla et al., 2015; Toronto Police Service, 2016; White, Todak, et al., 2018).
Additionally, Young and Ready (2015) have found that officer receptivity to BWCs may also be influ-
enced by participating in shared events with other officers who are wearing BWCs. Overall, the most
likely reason for the positive (or improved) feelings for BWCs is that officers see BWCs as protecting
themselves from the public, in particular, from frivolous complaints or one-sided stories about officer
conduct (Fouche, 2014; Goetschel & Peha, 2017; Koen, 2016; McLean et al., 2015; Owens & Finn,
2018; Pelfrey & Keener, 2016). Granted, some survey results have indicated that some officers believe
BWCs would improve their behavior or performance (see Edmonton Police Service, 2015; Gramaglia
& Phillips, 2017; Jennings et al., 2014, 2015; Makin, 2016; McLean et al., 2015; Tankebe & Ariel,
2016; White, Todak et al., 2018). In contrary studies, however, officers have been found to be skeptical
of such an effect (Pelfrey & Keener, 2016), especially after experiencing BWCs (Headley et al.,
2017).
Another value that officers see in BWCs is in improving the quality and availability of evidence
they might need to charge individuals with crimes (Gaub et al., 2018; Goodall, 2007; Jennings et al.,
2015; Katz et al., 2014; Pelfrey & Keener, 2016; White, Todak, et al., 2018).10 Some officers also use
BWC footage to help them write reports that are more consistent with the interactions they had with
citizens, rather than rely on their memory.
The positive perceptions of BWCs discovered in these surveys are in some ways surprising.
The notion that officers grow increasingly positive about a technology intended to increase their
accountability in light of negative circumstances could be construed as indicative of a significant
incongruence between citizen and police perceptions and expectations about this technology. Officers
may perceive that BWCs do not necessarily increase their accountability or change their behavior but
12 LUM ET AL.
rather, the accountability of citizens with regard to frivolous complaints or citizen behavior (see a
more general discussion of police and video by Sandhu, 2017, who shows similar findings). This point
was also indirectly confirmed by Merola, Lum, Koper, and Scherer (2016) who found that most BWC
footage used by prosecutors was not used to prosecute police misconduct but citizen misconduct.
Put simply, officers and citizens both seem to believe that BWCs can protect them from each other.
These conflicting expectations may reflect a larger dysfunction within police–citizen relationships
that BWCs may illuminate but not remedy.
The collective survey results also reveal important nuances that illustrate a more complicated picture
of the receptivity of BWCs by officers. For example, the study findings that do not paint a positive
outlook of BWCs by officers often tie negative reactions to specific concerns. As an example, Katz
et al. (2014) discovered that resistance to BWCs was partially connected to technical difficulties (i.e.,
the long time it took to download data) or to how it impacted their work or workload (i.e., lengthening
the time to complete reports), a finding consistent with other police technology literature (see review
in Koper et al., 2015). Both the officers in Katz et al.’s and in Newell and Greidanus's (2018) surveys
complained that BWC footage might be used against them and that it might make officers more
hesitant in their duties (see also Edmonton Police Service, 2015; McLean et al., 2015). Gaub, Choate,
Todak, Katz, and White (2016) reported significant variation across different departments regarding
officer perceptions of BWCs. Although over time each agency's officers reported improved percep-
tions of BWCs, they also became more cynical about the impact that BWCs would have on citizens
(also found by Headley et al., 2017, as well as by White, Todak, et al., 2018). Officers also raised
concerns in these surveys about cameras restricting their discretion or reducing their engagement in
the community.
Additionally, broader organizational and social network factors may be at play in officer receptivity
to BWCs, although this evidence is far from conclusive. For example, Kyle and White (2017) found
that attitudes toward BWCs may be conditioned by several factors—most interestingly, officer
perceptions of organizational justice. In other words, the greater the level of organizational justice
that an officer perceived from his or her organization, the more positive view he or she had about
BWCs. Relatedly, Tankebe and Ariel (2016) also found that officers who were more committed to
their agencies were less cynical about cameras and less resistant to BWCs. In a replication of Kyle
and White (2017) in a different agency, however, Lawshe (2018) did not find that perceptions of
organizational justice impacted officers’ views of BWCs. Similarly, Huff, Katz, and Webb (2018)
found no relationship between perceptions of organizational justice and receptivity or resistance to
wearing BWCs. Nor was receptivity to BWCs related to an officer's past levels of self-initiated activity,
use of force incidents, or citizen complaints.
5IMPACT OF BODY-WORN CAMERAS ON CITIZEN
BEHAVIOR
At least 16 studies were aimed at examining the impact of BWCs on citizen behavior (two were
focused on citizens’ perceptions of their behavior but are included). Although much less examined
than the impact of BWCs on officer behavior, the researchers behind these studies tried to measure
how BWCs impact citizen compliance to police commands or their physical response to police actions,
which were often measured by reports of resisting arrest or assaults on officers. Within this area, we
also discuss studies that were focused on the willingness of victims or witnesses to call the police and
to cooperate in criminal investigations. Furthermore, we consider studies in which scholars tried to
assess whether BWCs deter criminal and disorderly conduct among citizens more generally.
LUM ET AL.13
5.1 Impact of BWCs on citizen compliance with police
In 11 of these studies, researchers investigated the impact of BWCs on an individual's compliance
with police. In two studies, they used multisite randomized controlled experimental designs to test
this impact (Ariel et al., 2016b, 2018), in one they used an experiment in a single agency (White,
Gaub, et al., 2018), in six they used quasi-experimental designs of varying quality (Grossmith et al.,
2015; Headley et al., 2017; Hedberg et al., 2016; Katz et al., 2014; Toronto Police Service, 2016;
White, Todak, & Gaub, 2017), in one they used a systematic social observation study (McCluskey
et al., 2019), and in one researchers used a weak pre- and postdesign (Barela, 2017). These researchers
applied measures such as assaults on officers, reports of resisting arrest, or reported officer injuries
(see Table 1:3a).
The results of these studies vary. The findings from three studies seem to show that wearing BWCs
increases assaults on officers (Ariel et al., 2016b, 2018 [although these assaults did not always lead
to injury]; Toronto Police Service, 2016). Ariel et al. (2018) try to explain this “paradoxical” effect:
Overall assaults went down in the agencies examined, yet officers wearing cameras had higher odds
of being assaulted than did their control counterparts (not wearing BWCs). They hypothesized that
once officers become aware of being observed by BWCs, this inhibits their ability to function in
ways that avoid being assaulted in high-stress situations. In six studies, however, scholars found no
significant differences between officers with and without BWCs in terms of assaults upon them or
reports of resisting arrest (Grossmith et al., 2015; Headley et al., 2017; Hedberg et al., 2016; Katz
et al., 2014; White et al., 2017; White, Gaub, et al., 2018). Indeed, White et al. (2017) were skeptical
of a “civilizing effect” of BWCs on citizen behavior.
5.2 Impact of BWCs on citizen willingness to call and cooperate with
the police
Aside from compliance by individuals who encounter the police, we know much less about other
ways that BWCs may impact citizen behavior. For example, one concern raised about BWCs is
that they may reduce people's willingness to call the police due to worries about personal privacy
(Lum et al., 2015). This hypothesis continues to remain untested (see Table 1:3b, 3c). Ariel (2016b)
indirectly examined this question, finding that people within low-crime places seem more willing
to call police when the police have BWCs, but this effect was not found in high-crime places
(although there was no evidence that citizens were aware that BWCs were being used in both types of
areas).
Furthermore, in only one study—Grossmith et al. (2015)—did researchers examine whether
BWCs impact citizens’ willingness to cooperate in criminal investigations using proxy measures for
cooperation. They found no differences in these proxy measures between cases handled by officers
with and without BWCs. Understanding willingness both to call the police for help and to cooperate
with investigations seems urgent today for some agencies who have experienced declines in their
detection and clearance rates of serious violence. If victim and witness cooperation is an important
factor in this decline, then understanding whether BWCs will further negatively impact cooperation
for agencies that are struggling to solve cases will be an important consideration for agencies trying
to improve case clearance.
In two studies, scholars use surveys to hypothesize about these effects. We include these studies in
Table 1:3c, but we caution the reader about drawing causal inferences from them. For example, in the
Toronto Police Service (2016) study, scholars found, when interviewing individuals retroactively, that
they did not feel BWCs would impact their willingness to talk to the police as a victim, although they
14 LUM ET AL.
might be less comfortable in an investigative or enforcement situation. The Edmonton Police Service
(2015) also found from a public survey that people may be willing to provide incident information to
an officer wearing a BWC, but they may not be willing to have an informal chat with the police. In
both of these studies, scholars did not gauge whether BWCs have these effects in practice (although
in the Toronto study, they did try to gauge this retroactively). What is needed, for example, is a study
aimed at comparing areas and officers with and without BWCs and the levels of 911 calls for service
over time, or a test in which police dispatchers ask individuals when they call whether they would like
officers to respond with or without BWCs activated. Studies focused on examining BWC impacts on
investigations might prove harder to design.
5.3 Impact of BWCs on citizen crime and disorder
Finally, in four studies, scholars examined the impact of BWCs on crime and disorder more generally,
which could be interpreted as an indirect measure of the influence of BWCs on citizen behavior.
In three studies in the United Kingdom, researchers hypothesized that visible BWCs may reduce
antisocial behavior or other crimes when officers with cameras are present (Ellis et al., 2015; Goodall,
2007; ODS Consulting, 2011). Small declines in crime and disorder after BWCs were seen, but these
studies employed weak designs. Furthermore, it is not clear whether or why BWCs would create
additional deterrent effects beyond those of officer presence. In stronger quasi-experimental study,
Ariel (2016b) reported no general deterrent effects of BWCs on crime.
6IMPACT OF BODY-WORN CAMERAS ON CITIZEN AND
COMMUNITY ATTITUDES ABOUT THE POLICE OR THE
CAMERAS
We located 16 studies in which researchers assessed citizen and community attitudes about BWCs
or how BWCs might impact citizen and community attitudes about the police. These studies were
aimed at examining general support for BWCs by citizens and communities or citizen satisfaction
with specific encounters with officers wearing cameras.
6.1 General support for BWCs by citizens
First, many study findings (as well as widespread media coverage) indicate that citizens have
supported police agencies acquiring BWCs and have high expectations for them with regard to
making the police more accountable and increasing citizen confidence in the police (see Table 1:4b).
This support also extends to those most likely to encounter BWCs—detained suspects of crime
(Taylor, Lee, Willis, & Gannoni, 2017) as well as to numerous stakeholders (i.e., lawyers, city council
members, business owners, and activists) who might be affected by police use of BWCs (Todak et al.,
2018).
Nevertheless, this support comes with important caveats. For example, Crow, Snyder, Crichlow, and
Smykla (2017) found that community support can be contingent on a community member's background
and concerns about the police. In their study, non-White and younger respondents saw fewer benefits
of BWCs (see also a similar finding by Sousa, Miethe, & Sakiyama, 2018). Kerrison, Cobbina, and
Bender (2018) in their interviews of Black residents in Baltimore City also found those residents were
skeptical of the use of BWCs and video by the police to secure police accountability, despite inter-
viewees’ general support for more video footage. Furthermore, Crow et al. (2017) reported that those
LUM ET AL.15
who perceived the police to be more procedurally fair and had more positive perceptions of police per-
formance saw more benefits of BWCs (also found by Merola & Lum, 2014, for license plate readers),
whereas those with greater fear of crime saw fewer benefits (but see, in contrast, Plumlee, 201811). The
challenge is that those who see fewer benefits may be more likely to have an interaction with an officer
wearing a camera. More broadly, this reflects a consistent finding in research: There are disparities
between the legitimacy afforded to the police by various groups, which does not seem to be remedied
by BWCs.
6.2 Impact of BWCs on specific citizen–police encounters
Some studies were aimed at examining citizen satisfaction with specific encounters with officers
wearing BWCs (Table 1:4a). We note that measures of citizen satisfaction could be approximate
measures for officer behavior or even citizen behavior or feelings in response to seeing a camera.
Here, the findings are less optimistic. For example, Goodison and Wilson (2017), in their randomized
controlled experiment, found no significant differences in citizens’ perceptions of police legitimacy,
satisfaction with the interaction, or views of police professionalism between those who interacted
with officers wearing or not wearing BWCs. These findings suggest that citizens’ satisfaction and
perceptions are likely conditioned by officers’ actions and how they treat and speak to people, not
just whether they are wearing BWCs, which in this case does not seem to have changed officers’
behaviors. (This is somewhat contrary to the findings of McCluskey et al., 2019, discussed earlier).
Interestingly, Goodison and Wilson suggested that their combined findings of a reduction in citizen
complaints against officers wearing cameras but no effect on citizen perceptions may indicate a weak
relationship between measures of complaints and perceptions of police encounters.
Related to this issue is whether citizens even realize an officer is wearing a camera. Just as officer
self-awareness may be affected by BWCs, so too might that of citizens, but this would require citizens
to know that they are being filmed (which could have positive or negative effects as discussed later
in this article). McClure et al. (2017) found that many citizens who interact with police cannot
remember whether officers were wearing BWCs (also discovered by White et al., 2017). This issue
is further confounded by additional interventions that officers with BWC are using to improve citizen
satisfaction with a specific encounter. For example, McClure et al. reported that officers’ use of
procedural justice scripts, rather than their wearing of BWCs, may be what creates greater satisfaction
in citizens’ interactions with police officers (as also hinted at by Goodison & Wilson, 2017). This
may also be the case in Mitchell et al.’s (2018) study of traffic officers and complaints; all officers
assigned to BWCs were given procedural justice scripts to relay to citizens stopped, which may be
what caused the decline in complaints those officers received.
6.3 Impact of BWCs on attitudes regarding privacy or fear
The findings regarding citizen privacy concerns about BWCs are similarly unclear. Crow et al. (2017),
Grossmith et al. (2015), and Toronto Police Service (2016) all found that survey respondents are
generally unconcerned about privacy (although the respondents in the Toronto study also said they
might be less likely to chat informally with officers wearing BWCs). The Edmonton Police Service
(2015) discovered that citizens were concerned about their privacy when asked in a survey but less
concerned when confronted with BWCs at checkpoints. The arrestees of Taylor et al.’s (2017) study
had disagreements about whether police should be able to record people, raising concerns about what
the police would do with videos that were captured.
16 LUM ET AL.
Often juxtaposed against privacy concerns are concerns about fear. White et al. (2017), for example,
reported that most citizens that knew they were being recorded expressed strong agreement that BWCs
made them feel safer and more confident in the police. Goodall (2007) also found that victims felt
safer when officers had BWCs. As mentioned previously, though, these general feelings might mask
variations across different race, ethnicity, age, or gender groups.
7IMPACT OF BODY-WORN CAMERAS ON CRIMINAL
INVESTIGATIONS
Improving accountability for police misconduct has been a primary motivation for advocates of BWCs.
Prosecutors, however, rarely bring cases against the police (Skolnick & Fyfe, 1993), and it remains to be
seen whether this will change much as a result of BWCs. In their study of the use of BWCs in the courts,
Merola et al. (2016) found that nearly all (93.0%) responding prosecutors’ offices in jurisdictions that
use BWCs use them primarily to prosecute citizens. Not surprisingly, 80.0% of responding prosecutors
in Merola et al.’s survey support BWC use by the police, and 63.0% feel cameras will assist prosecutors
more than defense attorneys. Only 8.3% of the respondents who were located in jurisdictions in which
BWCs were available had ever used BWC footage in a case brought against an officer. Therefore, it is
not surprising that we currently do not know the impact of BWCs on the investigation of officer actions.
Instead, the seven12 policing studies in this area were aimed at examining whether BWCs can
assist with the investigation and resolution of crimes and whether BWCs can increase the rate of
guilty pleas, charges filed, or convictions against suspects. As mentioned, officers perceive these
to be benefits of BWCs. The findings from three studies in the United Kingdom (Ellis et al., 2015;
Goodall, 2007; ODS Consulting, 2011) revealed that BWCs may increase detection and clearance of
criminal investigations, as well as the rate of guilty pleas. Conclusions from these studies should be
taken cautiously, however, given the weaknesses in their research designs. Nevertheless, the findings
from stronger studies also reveal that BWCs have investigative benefits. Owens, Mann, and Mckenna
(2014), using an experimental design, found that issuing officers BWCs could increase the proportion
of detections that resulted in a criminal charge for domestic violence incidents (although they were
unable to determine the impact of BWCs on guilty pleas and sentencing). Morrow, Katz, and Choate,
in their recent study on intimate partner violence (2016; see earlier Katz et al., 2014), found that BWC
footage can make it easier for officers to pursue prosecution even without victim cooperation and that
cases may be more likely to be charged or result in a guilty plea or verdict at trial.13
8BODY-WORN CAMERAS AND POLICE ORGANIZATIONS
A final area of research that has been the least examined is the impact that BWCs have on police
organizations. In studies on police technologies, scholars have found that technologies often have
unintended consequences on police organizations and may not deliver on their expectations (Chan
et al., 2001; Koper et al., 2015; Lum et al., 2017; Manning, 2008). For example, proponents of BWCs
have high expectations of them for police organizations, believing that they can improve training,
tighten accountability structures and disciplinary systems and practices, or sharpen supervisory
practices. But skeptics argue that BWCs place undue financial burdens on agencies with regard to
maintaining the technology and hiring personnel to process videos. Some survey research findings
indicate that officers fear that BWCs may further damage their relationships with supervisors and
command staff or create a “robotic” culture among officers.
LUM ET AL.17
At the time of this review, the actual—as opposed to the perceived—effects of BWCs on law
enforcement organizations were still not well understood. In Table 1:6, we highlight some studies that
serve as starting points for these conversations. For example, in terms of whether BWCs can impact
police training, Phelps, Strype, Le Bellu, Lahlou, and Aandal (2018), in their quasi-experimental study
using BWCs for replay and decision-reflection, found little difference between groups using BWCs
and those not using BWCs in terms of police identity, reflective thinking, peer learning, or attitudes
toward training. They did find, however, that officers who trained with BWCs were more likely than
a non-BWC control group to say that they had identified mistakes during their training, and to recall
more instances of learning and reflection. Much more research is needed to understand whether BWC
footage can help officers either in-field or academy training to learn and retain concepts and skills
better, and whether that learning then has effects on their behavior (a question for training more
generally). Koen (2016) found modest evidence that BWCs could be used for training in his study of a
small agency, and BWCs were also found to be used for training by the Toronto Police Service (2016).
Nonetheless, it was not clear whether BWCs had been successfully (i.e., consistently, systematically,
or mandatorily) incorporated into training in either of these studies, or whether such training with
BWCs affected officers’ behaviors as a result (Koen, Willis, & Mastrofski, 2018). Finally, we also do
not know to what extent BWCs are currently being used for training.
In regard to workload and costs, the Toronto Police Service (2016) found officers with BWCs had
an increased number of arrests but a decline in discretionary warnings, the former requiring more work
than the latter. At the same time, they also found that the time it took for an agency to investigate a
complaint against an officer declined for officers wearing BWCs, implying cost-savings. Similar cost–
benefits were also reported by Braga, Coldren, Sousa, Rodriuez, and Alper (2017),14 who estimated that
the Las Vegas Metropolitan Police Department could potentially garner a net annual savings of around
$4 million per year in costs associated with investigating complaints. We do not know, however, the
impact that BWCs have on disciplinary and accountability systems more generally, such as on pro-
cesses related to officer misconduct or officer-involved shootings, all of which have implications for
agency costs.
Related to workload is how BWCs might impact officer burnout, an issue specifically examined
by Adams and Mastracci (2018). They reported that officer burnout is greater for officers who wear
BWCs, and that cameras can reduce officers’ perceptions of how much their organizations support
them. Nevertheless, positive perceptions of organizational support can mitigate burnout potentially
caused by BWCs.
Perhaps more important to point out is that technologies often do not reform organizations insomuch
as organizations shape (or inhibit) the use of the technology (Lum et al., 2017; Manning, 2008). Both
citizens and police leaders might expect BWCs to strengthen the accountability infrastructure in polic-
ing (i.e., procedures for complaints and discipline; supervision, mentorship, and oversight; or recording
and accounting of actions). The introduction of BWCs, however, may not achieve this goal if the
existing accountability mechanisms in the agency are weak. For example, mentorship and supervision
by first-line supervisors of line officers are important components of a healthy accountability structure
that can foster a dynamic and transformational learning environment. Yet, if an agency does not value
such mentorship or supervision, or does not have tangible ways to strengthen the officer and first-line
supervisor relationship in these ways, then it is unlikely that BWCs can improve this organizational
weakness. The inability of BWCs to impact accountability structures may already be seen in findings
that cameras are primarily used by the police (and prosecutors) to increase the accountability of cit-
izens, not officers. The unintended consequences frequently seen from technology are often the result
of technology being filtered through the existing values, systems, and cultures of the organization, not
hoped-for ones.
18 LUM ET AL.
9DISCUSSION
Body-worn cameras are one of the most rapidly diffusing technologies in law enforcement. Unlike
many other adopted technologies, researchers have taken a high level of interest in BWCs, and they
have tried to keep up with the adoption through extensive research and analysis of both the impacts
of BWCs and how BWCs are perceived by officers and communities alike. In total, we examined
70 empirical studies in this review in which scholars spoke to the impact of BWCs on officer and
citizen behavior, officer and citizen attitudes, investigations, and police organizations.
What is the picture that seems to be emerging from this research? In general, officers seem
supportive of BWCs, particularly as they gain more experience with them. Increasingly, officers value
BWCs as a tool for their protection (against false or exaggerated accusations of wrongdoing), for
evidence collection (which may be bolstered by prosecutors’ support for BWCs), and for accurate
reporting. It may be fair to say, however, that BWCs have not produced dramatic changes in police
behavior, for better or worse. Although early findings indicated BWCs reduce the use of force by
officers, more recent findings have been mixed, perhaps in part as a result of variation in agency
policies regarding how the devices should be used. A more encouraging finding is that BWCs seem to
reduce complaints against officers. The question remains, then, as to whether and to what degree these
changes reflect citizens’ reporting behaviors or improvements in officers’ behavior or their interactions
with citizens. On a related note, it is not clear from available evidence that BWCs improve citizens’
satisfaction with police encounters, as might be expected if BWCs were having substantial effects on
police behavior. In sum, BWCs may curb some of the worst police behaviors but have little impact
otherwise.
Similarly, fears of depolicing from the use of BWCs have not been realized. Arrests seem as
likely to increase as to decrease with the use of BWCs, perhaps suggesting that adoption of the
cameras leads to more formal and legalistic responses to citizens in some contexts. Otherwise, BWCs
do not seem to have discouraged most proactive field contacts or officer-initiated activities. But
this issue is complex; citizens may want some types of police proactivity to decline (for example,
stop-question-and-frisks or misdemeanor arrests for recreational drug use) but may want other types
of proactivity to increase (problem-solving, community engagement, targeted patrol in high crime
places). From an evidence-based perspective, it would seem most appropriate to hope that BWCs do
not cause police to stop carrying out proactive activities that can prevent and reduce crime and that
do not create negative reactions from citizens. But some proactive activities might do both; therefore,
expecting BWCs to resolve this challenge is overly optimistic.
For their part, citizens are also generally supportive of police using BWCs. Nonetheless, it is not clear
that BWCs improve their views of police or their behaviors toward police. One exception is that BWCs
may discourage citizens from filing complaints against police in some contexts (perhaps depending on
the seriousness of the officer's misconduct), but this will not necessarily translate into citizens having
more positive views of police. BWCs also might exacerbate an already challenged relationship between
citizens and the police, especially if citizens expect cameras to be used to increase police accountability
and transparency, but officers primarily use them to increase the accountability of citizens.
Overall, then, perhaps anticipated effects from BWCs have been overestimated. If true, this should
not be surprising, given the mixed and modest effects that technologies often have more generally in
policing (Chan et al., 2001; Koper et al., 2015). Several caveats are in order, however. Although the
number of BWC studies is large overall, the number available to evaluate any particular outcome is
still often small, and findings are thus subject to change. As the evidence base grows, the use of more
sophisticated meta-analyses of results will also provide better estimates of average effect sizes and
contextual factors associated with desired and undesired outcomes.
LUM ET AL.19
Furthermore, the research evidence is still lacking on many important questions. For example, will
BWCs affect legality and disparity in police actions? Will they change citizens’ willingness to report
crime and cooperate in police investigations? Are there differential impacts of BWCs on different
groups of people or officers? Perhaps most importantly, the effects of BWCs on police organizations
are still unknown. If BWCs are to produce substantial changes in police behavior and performance,
these changes are most likely to come through their effects on processes in police organizations, par-
ticularly those pertaining to training, supervision, and investigation of police misconduct. Determining
how BWCs affect the processes and outcomes of internal police investigations is particularly central
to assessing whether BWCs achieve the purpose that was arguably the main driver of their adoption
(i.e., improving transparency and accountability in the investigation of serious police misconduct,
particularly surrounding the use of deadly force). These changes will come slowly, if at all, and will
require long-term attention from the field. Nevertheless, they may be the most consequential for
police–community relations and police legitimacy in the long run.
In the meantime, agencies will almost certainly continue to adopt BWCs. Given the ubiquity of
personal video and audio recording devices, more and more police agencies are likely to conclude
that they need to have their own recording of events for police–citizen encounters that go bad. There
is also likely to be a growing expectation among the public that adopting BWCs is a marker of a
responsive, transparent, and legitimate police organization. This will put considerable technical and
financial strains on police (and prosecutors) that will also need further attention in cost efficiency
analysis. Nevertheless, the behavioral changes in the field may be modest and mixed, at least in the
short run.
ENDNOTES
1See the Body-worn Camera Toolkit at the following URL: bja.gov/bwc/.
2In some cases, we did not include a study that was technically empirical but of poor methodological quality to be
included. For example, this might include a survey of 10 individuals in which no sampling frame or design was
provided.
3These included Criminal Justice Abstracts, National Criminal Justice Reference Service, ProQuest, Google Scholar,
Social Science Citation Index, and all criminal justice-related databases available in the George Mason University
library system.
4We have been contracted by the Campbell Collaboration to conduct systematic reviews (which will include meta-
analyses) of the specific areas of BWC research discussed in this article. In that review, we will present deeper analysis
of the various methods (and methodological challenges) of each article as well as of the context and location of each
research study to examine how relationships between study design, location, timing, and methodological approach
contribute to the findings of BWC research.
5This estimate is an approximation. In some studies, scholars pooled multiple analyses together. Other studies, which
we list as distinct because they are published in different outlets with different outcomes, were conducted by the
same authors and may have some overlap. Some later studies were peer-reviewed publications of portions of previous
reports or unpublished documents. In these cases, we used the most recent, peer-reviewed article, except when an
earlier report had findings that were not present in the later peer-reviewed article.
6We distinguish these studies from those that were aimed at examining officers’ reflective perceptions of the impact
of BWCs on their behavior, which are included in the next section.
7Michael White, Janne Gaub, and their colleagues have developed a handy online resource that summarizes stud-
ies in which the impact of BWCs on complaints and use of force has been examined. These tools are located
at bwctta.com/resources/bwc-resources/impacts-bwcs-use-force-directory-outcomes and bwctta.com/resources/
bwc-resources/impact-bwcs-citizen-complaints-directory-outcomes.
20 LUM ET AL.
8This study was based on Farrar's master's thesis at Cambridge University in the United Kingdom, which we cite as
Farrar, 2012; Farrar & Ariel, 2013. Further citations regarding this study, however, refer to the peer-reviewed article:
Ariel et al. (2015).
9For example, in two non-U.S. studies, scholars found that BWCs were associated with declines in use of force (Ariel
et al., 2016a; Henstock & Ariel, 2017), and in another two studies, they found nonsignificant effects (Edmonton
Police Service, 2015; Toronto Police Service, 2016). Ariel et al. (2016a) showed both declines and increases in use
of force, depending on the protocols followed.
10 Todak, Gaub, and White's (2018) findings also seem to indicate that some of the external stakeholders that they
interviewed also saw the evidentiary value of BWCs.
11 Interestingly, Plumlee (2018), in his study of university students’ perceptions of BWCs, found somewhat contrary
findings to Crow et al. (2017). Plumlee found that those students who perceive greater inequity in minority-citizen
and police officer relations (perhaps suggesting less procedural fairness) feel BWCs can be more beneficial. This
finding, however, was also conditioned on the student's major; interestingly, criminal justice students were much less
likely to see positive benefits of BWCs than were noncriminal justice majors.
12 We include Merola et al.’s (2016) study in this category because of its empirical relevance to this area. Merola et al.,
however, conducted a nationwide survey of prosecutor offices and their perceptions about BWCs (with regard to
investigations and other issues) and not a test of the effect of BWCs on investigations.
13 Yokum et al. (2017) also examined the effects of BWCs on judicial outcomes. As this analysis lacked data to determine
this outcome, however, we do not report those findings here.
14 Braga, Sousa, et al.’s (2018) study is the peer-reviewed publication of the Braga et al. (2017) report, and it is used
in this article. Nevertheless, only Braga et al. (2017) reported the cost–benefits analysis, which is why we cite to the
non–peer-reviewed report here.
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26 LUM ET AL.
AUTHORS'BIOGRAPHIES
Cynthia Lum is professor of criminology, law and society at George Mason University (GMU). She
is also the director of GMU's Center for Evidence-Based Crime Policy. Professor Lum's research
interests including evidence-based policing and law enforcement organizations, crime prevention,
and evaluation research. Her recent book, with Christopher Koper, is Evidence-Based Policing:
Translating Research into Practice (Oxford University Press).
Megan Stoltz is a doctoral student in criminology, law and society at George Mason University
(GMU). She received her master's degree in forensic psychology from Marymount University. She
is a research assistant at GMU's Center for Evidence-Based Crime Policy. Her interests include
evidence-based crime policy, legal psychology, and the intersection of mental health and the crim-
inal justice system.
Christopher S. Koper is an associate professor in the Department of Criminology, Law and Soci-
ety at George Mason University and the principal fellow of Mason's Center for Evidence-Based
Crime Policy. He specializes in issues related to policing, firearms policy, program evaluation, and
evidence-based crime policy. He is the co-author (with Cynthia Lum) of Evidence-Based Policing:
Translating Research into Practice (Oxford University Press).
J. Amber Scherer is a doctoral candidate in the Criminology, Law and Society Department at
George Mason University (GMU). She is also a research associate in GMU's Center for Evidence-
Based Crime Policy (CEBCP). Mrs. Scherer's research interests include evidence-based policing,
investigative effectiveness, evaluation research, and psychology in the criminal justice system.
How to cite this article: Lum C, Stoltz M, Koper CS, Scherer JA. Research on body-
worn cameras: What we know, what we need to know. Criminol Public Policy. 2019;1–26.
https://doi.org/10.1111/1745-9133.12412
