Police use of force is at the forefront of public awareness in many countries. Body-worn videos (BWVs) have been proposed as a new way of reducing police use of force, as well as assaults against officers. To date, only a handful of peer-reviewed randomised trials have looked at the effectiveness of BWVs, primarily focusing on use of force and complaints. We sought to replicate these studies, adding assaults against police officers as an additional outcome. Using a prospective meta-analysis of multi-site, multi-national randomised controlled trials from 10 discrete tests with a total population of +2 million, and 2.2 million police officer-hours, we assess the effect of BWVs on the rates of (i) police use of force and (ii) assaults against officers. Averaged over 10 trials, BWVs had no effect on police use of force (d = 0.021; SE = 0.056; 95% CI: -0.089-0.130), but led to an increased rate of assaults against officers wearing cameras (d = 0.176; SE = 0.058; 95% CI: 0.061-0.290). As there is evidence that cameras may increase the risk of assaults against officers, more attention should be paid to how these devices are implemented. Likewise, since other public-facing organisations are considering equipping their staff with BWVs (e.g. firefighters, private security, traffic wardens), the findings on risks associated with BWVs are transferrable to those occupations as well.

Objectives Our multisite randomized controlled trial reported that police body-worn cameras (BWCs) had, on average, no effect on recorded incidents of police use of force. In some sites, rates of use of force decreased and in others increased. We wanted to understand these counter-intuitive findings and report pre-specified subgroup analyses related to officers' discretion on activating the BWCs. Methods Using pre-established criteria for experimental protocol breakdown in terms of treatment integrity, ten experimental sites were subgrouped into Bhigh-compliance( no officer discretion applied to when and where BWCs should be used; n = 3), Bno-compliance^(treatment integrity failure in both treatment and control conditions; n = 4), and tests where officers applied discretion during treatment group but followed protocol in control conditions only (n = 4). Results When officers complied with the experimental protocol and did not use discretion, use of force rates were 37 % lower [SMD = (−.346); SE = .137; 95 % CI (−.614) -(−.077)]; when officers did not comply with treatment protocol (i.e., officers chose when to turn cameras on/off), use of force rates were 71 % higher [SMD = .392; SE = .130; 95 % CI (.136) -(.647)], compared to control conditions. When full discretion (i.e., overall breakdown of protocol) was applied to both treatment and control conditions, null effects were registered [SMD = .009; SE=.070; 95 % CI (−.127) -(.146)], compared to control conditions. Conclusions BWCs can reduce police use of force when then officers' discretion to turn cameras on or off is minimized-in terms of both case types as well as individual incidents. BWCs ought to be switched on and the recording announced to suspects at early stages of police-public interactions. Future BWCs tests should pay close attention to adherence to experimental protocols.

Objectives Recently, scholars have applied self-awareness theory to explain why bodyworn cameras (BWCs) affect encounters between the public and police, with its most immediate manifestation being a reduction in the use of force by and complaints against police. In this study, we report on the paradoxical effects of BWCs in the context of assaults on officers. Methods A multisite randomized controlled trial in ten departments, with officers wearing (or not wearing) BWCs based on random assignment of shifts. Odds ratios are used to estimate the treatment effect on assaults, along with Bone study removedŝ ensitivity analyses. Further subgroup analyses are performed in terms of varying degrees of officers' discretion, to enhance the practical applications of this multisite experiment. Finally, before-analyses are applied as well, control shifts (M = 28.38; SD = 15.99), which translate into 37% higher odds of assault in treatment shifts than in control conditions. The perverse direction and relative magnitude in each experimental site in eight out of ten sites were consistent. The backfiring treatment effect was substantially more pronounced in low discretion sites, i.e., where officers strongly followed the experimental protocol (OR = 2.565; 95% CI 1.792, 3.672). At the same time, before-after analyses show that assaults were overall reduced by 61% in the participating police departments, thus suggesting paradoxical effects.Conclusions We explain these findings using self-awareness theory. Once self-aware that their performance is being observed by BWCs, officers become at risk of being assaulted. Results suggest that under some circumstances, self-awareness can lead to excessive self-inspection that strips power-holders of their ability to function under extreme situations. This mechanism is potentially a function of Bover-deterrence^. The study further demonstrates the benefits of applying psychosocial theories to the study of social control and deterrence theories more broadly, with a robust and falsifiable mechanism that explains the conditions under which being observed stimulates either appropriate or perverse consequences.

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There is, at present, a worldwide uncontrolled social experiment taking place within policing on body-worn-cameras, without much evidence from controlled studies  Our randomized-controlled-trial aims to reveal the conditions under which body-worncameras can effect arrest dynamics in England and Wales  Scholars interested in use of force should differentiate between "compliant handcuffs" which are part of the arrest procedure rather than use-of-force per se, and "noncompliant handcuffing", which form a step on the force continuum.  Overall, the odds of use of force while using body-worn-cameras are 50% lower than control conditions. However, the effect is statistically significant only when compliant handcuffing is removed from the definition of "use of force".  Instead, the odds of reporting compliant handcuffing under treatment conditions increased by 40% compared to control conditions, which is likely to be a result of enhanced police accountability.  Overall, the effect of body-worn cameras in frontline policing is concentrated on "openend tactics" rather than more aggressive force responses (e.g., batons, Taser discharges, pepper spray, etc.).