Study 1
Ariel and colleagues (2016) evaluated the impact of police-body worn cameras on officer use of force and assaults against officers. This is the first study to examine assaults against officers as an outcome measure for police body-worn cameras. The authors conducted a prospective meta-analysis of 10 randomized controlled trials involving 2,122 police officers from eight police departments. Two of the police forces covered two separate geographic areas that were included in the trial; this accounts for the greater number of trials than police forces. The eight police forces were located in the United States (Ventura and Rialto, California) and in the United Kingdom (West Midlands, Cambridgeshire, and Northern Ireland).
Each trial randomly assigned officer shifts to either treatment (with cameras) or control (no cameras) conditions on a weekly basis. Of a total of 4,915 shifts, 2,447 shifts were assigned to the treatment group, and 2,468 shifts were assigned to the control group. There were no differences between treatment and control conditions in terms of the distribution of shifts.
The outcomes included whether an officer used force during a shift (if so, how many times) and whether officers were assaulted (if so, how many times). These were standardized as rates per 1,000 per shift, because the police forces ranged in size. To mitigate differences in how ”force” was defined across the eight different sites, the analyses focused on any physical restraint beyond the use of verbal commands during an arrest (for example, if an officer used pepper spray). Assaults against police officers were self-reported based on routine reporting requirements.
The Comprehensive Meta-Analysis Version 2 software was used to synthesize the results from the trials and present the overall results, using standardized difference of means to compare treatment and control conditions across all sites. Subgroup analyses were conducted.