Body Worn Cameras are spreading worldwide, under the assumption that police performance, conduct, accountability, and legitimacy, in the eyes of the public, are enhanced as a result of using these devices. In addition, suspects’ demeanor during police–public engagements is hypothesized to change as a result of the video-recording of the encounter. For both parties—officers and suspects—the theoretical mechanism that underpins these behavioral changes is deterrence theory, self-awareness theory, or both. Yet evidence on the efficacy of Body Worn Cameras remains largely anecdotal, with only one rigorous study, from a small force in Rialto, California, validating the hypotheses. How Body Worn Cameras affect police–public interactions in large police departments remains unknown, as does their effect on other outcomes, such as arrests. With one Denver police district serving as the treatment area and five other districts within a large metropolitan area serving as comparisons, we offer mixed findings as in the Rialto Experiment, not least in terms of effect magnitudes.
Adjusted odds-ratios suggest a significant 35% lower odds for citizens’ complaints against the police use of force, but 14% greater odds for a complaint against misconduct, when Body Worn Cameras are used. No discernable effect was detected on the odds of use of force at the aggregate, compared to control conditions (OR=0.928; p>0.1). Finally, arrest rates dropped significantly, with the odds of an arrest when Body Worn Cameras not present is 18% higher than the odds under treatment conditions. The outcomes are contextualized within the framework of reactive emergency calls for service rather than proactive policing. We further discuss officers’ decisions and the degree of the necessity of arrest in policing more broadly, because the burden of proof for tangible evidence necessary for making a legal arrest can be challenged with the evidence produced by Body Worn Cameras: officers become “cautious” about arresting suspects when Body Worn Cameras are present. Limitations associated with the lack of randomly assigned comparison units are discussed, as well, with practical recommendations for future research on Body Worn Cameras.