A new study involving more than 2,000 police officers from eight departments in the United States and the United Kingdom produced some surprising results: Assaults on police officers who wore body cameras went up, while police use-of-force incidents remained unchanged.

That flies in the face of all other studies I’ve seen so far, which have shown body cameras to reduce the incidence of both.

But there’s a catch.

The researchers set out a protocol for officers allocated cameras during the trials: record all stages of every police-public interaction, and issue a warning of filming at the outset. However, many officers preferred to use their discretion, activating cameras depending on the situation.
Researchers found that during shifts with cameras in which officers stuck closer to the protocol, police use-of-force fell by 37% over camera-free shifts. During shifts in which officers tended to use their discretion, police use-of-force actually rose 71% over camera-free shifts.
“The combination of the camera plus the early warning creates awareness that the encounter is being filmed, modifying the behaviour of all involved,” said [principal] investigator Barak Ariel from the University of Cambridge’s Institute of Criminology.
“If an officer decides to announce mid-interaction they are beginning to film, for example, that could provoke a reaction that results in use-of-force,” Ariel said. “Our data suggests this could be what is driving the results.”

Letting the officers choose when to turn on the cameras would also seem to defeat the goals of transparency and accountability. Telling them when to use the cameras but then failing to hold them accountable when they fail to follow those procedures isn’t all that different from having no procedures at all.

The takeaway from this study is not that body cameras fail to minimize violence between police and citizens, but that it’s critical that (a) body cameras are implemented with sound policies and procedures to govern their use, and (b) police officers are required to abide by those policies.