Controversial moves to place cameras on coppers have reduced the number of Police complaints dramatically.

A study from Cambridge University shows complaints against police officers dropped when departments began using body cameras. But even more surprising is that the data suggests everyone is on their best behaviour whether the cameras are present or not.

The study was reported in the journal Criminal Justice and Behavior, which we get for the spot the criminal competition. The data was collected in seven police departments in the UK and US, and represents over 1.4 million hours logged by 1,847 officers in 2014 and 2015; the researchers published their data last week.

Officers were randomly assigned to wear or not wear cameras week by week – about half would be wearing them at any given time – and had to keep them on during all encounters. The authors used complaints against police as a metric because they’re easy to measure, an established practice in most police forces and give a good ballpark of the frequency of problematic behaviour.

In the year before the study, 1,539 complaints in total were filed against officers; at the end of the body camera experiment, the year had only yielded 113 complaints.  But against all expectations, there was no significant difference in complaints between officers wearing cameras that week and those going without.

The study’s lead author, Barak Ariel said that it was possible that repeated exposure to the surveillance of the cameras meant that officers changed their reactive behaviour on the streets — changes that proved more effective and so stuck.

“With a complaints reduction of nearly 100 percent across the board, we find it difficult to consider alternatives, to be honest.”