Body cameras have been receiving a lot of attention as a tool to increase police accountability and now a study shows theyre pretty effective at decreasing complaints against police, too.

The Cambridge University study, published this month in the journal Criminal Justice and Behavior, found that complaints against police officers filed by citizens decreased substantially after officers began wearing the monitoring devices.

The study followed seven police departments across the U.S. and the U.K., and tracked the number of complaints filed against the roughly 2,000 officers in the year before they began wearing body cameras, then compared that number to the complaints filed in the year after.

In all, complaints dropped from 1,539 in the year before to just 113 for all seven departments in the year after a dramatic reduction of 93 percent.

Of the seven departments studied, one saw a 100 percent decrease in the number of complaints filed. The other six departments saw drops of 98 percent, 94 percent, 94 percent, 88 percent, 88 percent and 44 percent.

I cannot think of any [other] single intervention in the history of policing that dramatically changed the way that officers behave, the way that suspects behave, and the way they interact with each other, lead author Dr. Barak Ariel told the BBC , reacting to the findings.

While the authors concede body cameras may not do much to improve the public perception of police legitimacy, which is a more deeply rooted issue, the devices do increase accountability for all parties involved including other officers who dont even wear cameras.

The researchers recorded a decrease in complaints filed against officers who worked in the same departments, but did not wear a body camera, a phenomenon the authors label contagious accountability.

Everyone was affected by it, the study found, even when the cameras were not in use, and collectively everyone in the department(s) attracted fewer complaints.