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New review of studies on police use of body-worn cameras questions whether technology benefits police, communities

In the past decade, many law enforcement agencies have adopted the use of body-worn cameras (BWCs) to improve police conduct, accountability, and transparency, especially when it comes to using force. But it is not yet known whether BWCs actually reduce officers’ use of force. A new meta-analysis examined 30 studies of law enforcement use of BWCs and found that the way BWCs are being used may not substantially affect most behavior by officers or citizens, though restricting officers’ discretion in turning on and off BWCs may reduce police use of force.

The meta-analysis, by researchers at George Mason University (GMU), appears in Campbell Systematic Reviews, the journal of the Campbell Collaboration,an international, voluntary, nonprofit research network that publishes systematic reviews. This review is both an update and a more specific analysis of the literature on BWCs from the authors’ 2019 review.

“Body-worn cameras are one of the most rapidly spreading and costly technologies used by police agencies today,” says Cynthia Lum, professor of criminology, law, and society at GMU, who led the study. “Amid high-profile officer-involved shooting incidents and protests, our review questions whether BWCs bring the expected benefits to the police and their communities: BWCs do not seem to affect officers’ or citizens’ behaviors in the ways initially hoped for by police leaders and citizens.”

Over the years, many citizens and community groups have supported adoption of BWCs, but some police and community members have expressed concern that BWCs might infringe on privacy, discourage citizens from reporting crimes, or cause officers to refrain from activities that may help prevent offending.

Using meta-analytic techniques to synthesize and analyze the magnitude of specific effects, researchers identified and examined 30 high-quality evaluations of BWCs published or available through September 2019, which contained 116 analyzed effects of BWCs across multiple outcomes. These outcomes included complaints against officers, use of force, assaults against officers, arrest activity, officers’ self-initiated activity, traffic stops and ticketing, field interviews and stop-and-frisks, calls for service, and incident reports.

“This review is critical to building the evidence base necessary for police agencies, municipalities, governments, and citizens to understand the best way to use BWCs,” said Asheley Van Ness, Arnold Ventures Director of Criminal Justice. “After a decade of using this technology, we’ve realized that asking the right questions is just as important as seeking the right answers.”

The meta-analysis concluded that substantial uncertainty remains about whether BWCs reduce officers’ use of force. However, variation in effects on use of force suggests that there may be conditions in which the cameras could be effective, although the authors suggest that more investigation is needed. Specifically, there is some indication that the use of BWCs were associated with less use of force when officers had no or limited discretion in activating these cameras. Yet even under these circumstances, results were inconclusive as to whether BWCs produced reductions that were statistically meaningful. The researchers also found that the effects of BWCs on the outcomes studied varied substantially across different contexts.

The review also found that overall, the way BWCs are currently used does not seem to affect other police and citizen behaviors in a significant or consistent manner, including officers’ self‐ initiated activities (including traffic stops and stop-and-frisks) or arrest behaviors. Nor do BWCs have clear effects on citizens’ calls to police, or on assaults or resistance against officers.

The meta-analysis shows that BWCs can reduce the number of citizen complaints against police officers, but it is unclear whether this finding signals an improvement in the quality of interactions between police and citizens or a change in reporting. Research has not addressed whether BWCs strengthen police accountability systems or relationships between police and citizens.

“Law-enforcement agencies that have or plan to acquire BWCs and the communities they serve should temper their expectations about the cameras’ effectiveness,” suggests Christopher Koper, associate professor of criminology, law, and society at GMU, who coauthored the study. “Police agencies should continue to test the ways police and citizens might benefit from using BWCs. Determining how to use cameras to reap long‐term gains of strengthening organizational accountability may be a better investment than the more short‐term gains we measured.” The research was supported by Arnold Ventures.

Summarized from Campbell Systematic Reviews, Body-Worn Cameras’ Effects on Police Officers and Citizen Behavior: A Systematic Review by Lum, C (George Mason University), Koper, CS (George Mason University), Wilson, DB (George Mason University), Stoltz, M (George Mason University), Goodier, M (George Mason University) et al. Copyright 2020 The Authors. Campbell Systematic Reviews published by John Wiley & Sons Ltd on behalf of The Campbell Collaboration. All rights reserved. The full article can be accessed at:

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Caitlin Kizielewicz
Crime and Justice Research Alliance
(412) 554-0074