Evaluating the Effects of Police Body-Worn Cameras: A Randomized Controlled Trial


David Yokum, Anita Ravishankar, Alexander Coppock

Full citation: 
Yokum, David, Anita Ravishankar, Alexander Coppock (2017). Evaluating the Effects of Police Body-Worn Cameras: A Randomized Controlled Trial. The DC Lab Working Paper, October 20, 2017.
Police officer body-worn cameras (BWCs) have been promoted as a technological mechanism that will improve policing and the perceived legitimacy of the police and legal institutions. While there is a national movement to deploy BWCs widely, evidence of their effectiveness is limited. To estimate the average effects of BWCs, we conducted a randomized controlled trial involving 2,224 Metropolitan Police Department (MPD) officers in Washington, DC. Our pre-analysis plan was publicly registered in advance. We compared officers randomly assigned to wear BWCs to officers in the control condition who did not wear BWCs. The primary outcomes of interest were documented uses of force and civilian complaints, although we also measure a variety of additional policing activities and judicial outcomes. We estimated very small average treatment effects on all measured outcomes, none of which rose to statistical significance. These results suggest that we should recalibrate our expectations of BWCs’ ability to induce large-scale behavioral changes in policing, particularly in contexts similar to Washington, DC.
Supplemental information: 

Link to working paper here.

Publication date: 
Publication type: 
Area of study: