Re-Examining Body-Worn Cameras

Sparked by the police killing of unarmed teenager Mike Brown, the 2014 Ferguson protests ignited a nation-wide conversation about police reform in the United States. To increase safety and accountability for officers and civilians, many lawmakers responded by requiring officers to wear body-worn cameras. A 2016 survey of police departments across the nation found 95% of respondents had committed to putting the use of body-worn cameras into practice or had already implemented the technology. In Chicago, former Mayor Rahm Emmanuel swiftly implemented a city-wide body-worn cameras program that outfitted more than 7,000 Chicago Police Department personnel with cameras within three years. After more highly publicized killings of Black Americans, researchers are re-examining the effectiveness of these technological reforms.

Proponents of body-worn cameras believe that the physical presence of the cameras has psychological effects on officers and civilians. They theorize that when someone knows they are being watched, they will alter their behavior to be more socially acceptable. Police will exercise caution before using force and civilians will be more conciliatory when interacting with police. Stakeholders in criminal and civil litigation tout the evidentiary value of body-worn cameras. They contend that the footage not only sheds light on the interaction, but also serves as highly probative initial or corroborating evidence. Finally, law enforcement leadership underscores their role in training and providing promotions.

A novel 2019 study conducted by David Yokum, Anita Ravishankar, and Alexander Coppock examined the use of body-worn cameras in police departments and found little evidence that their usage increased officer or civilian safety. Yokum et. al. focused the study on the Washington, D.C. Metropolitan Police Department during the 2015 implementation of body-worn cameras. The entirety of the Metropolitan Police Department’s 2,225 officers from its seven districts and three special units were assigned to either a treatment group who would wear body-worn cameras or a control group who would not. To ensure randomization, the authors used a block randomized assignment procedure before designating individuals to treatment or control groups. This accounted for differences between officers’ units of assignments—patrol officer within districts or a specialized unit. The authors divided the participants into groups, or blocks, whose assigned units were similar to one another to ensure both the treatment and control groups received balanced numbers of officers from assigned units. Furthermore, an additional block-randomization was implemented to account for various background characteristics such as race, gender, and length of service on the force to ensure similar characteristics for both treatment and control groups.

In evaluating the effectiveness of body-worn cameras, the researchers incorporated four outcome variables into their analytical model. First was police self-reported use of force, designated as serious use of force where the officer may have used weapons or caused injuries or designated as other. Researchers predicted that the treatment group outfitted with cameras would have less frequent severe use-of-force reports and an increase in other use-of-force reports. The second outcome variable was civilian complaints to MPD or the Office of Police Complaints and case disposition. The third was police activity, which metrics included issuing traffic tickets or warnings, “reports taken on particular types of calls for service,” certain types of arrests, and injuries sustained in the line of duty. This allowed the researchers to examine how civilians interact with police. Lastly was the number of hours spent in court and the judicial outcomes of criminal cases stemming from MPD arrests. Yokum et al. found very minimal estimates of all average treatment effects across all four outcome areas, none of which rose to the level of statistical significance. Notably, they found an increase in use-of-force in the treatment group during their study, though this is also statistically insignificant.

Yokum et. al.’s findings suggests that body-worn cameras are not altering the trajectory of police-civilian interaction. Given that the implementation, technology, and storage of these cameras and their footage can cost upwards of $700 per unit, we must call into question its universal adoption. As new conversations emerge about what policing should and shouldn’t look like, it’s crucial to consider what we’ve learned since Ferguson. Defunding and demilitarization of police is becoming a reality in many jurisdictions while simultaneously other jurisdictions are committing to fully outfit their staff with body-worn cameras. Studies like this may help local legislators parse out the best course of action for police reform or help safely make cuts to ineffective and expensive services and technology within existing departments.

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Yokum, David, Anita Ravishankar, and Alexander Coppock. 2019. “A randomized control trial evaluating the effects of police body-worn cameras.” Proceedings of the National Academy of Sciences 116, no. 21: 10329-10332. https://doi.org/10.1073/pnas.1814773116.