Police use of body cameras might not have any effect on police behavior or citizen complaints, according to a new study.
The study, conducted in Washington, D.C., found there was no significant difference between the number of citizen complaints or the amount of force used by police wearing body cams and those who weren't.
That seems to contradict public perception of body cams, but it also contradicts other studies that found them to be a useful tool in lowering use of force by police.
But this study is a lot larger than previous studies. Where some older studies used tens of subjects, this newer study analyzed data from over 2,000 officers.
Still, it might be hard to generalize the data from D.C. out to other police departments. In 2001, the D.C. Metropolitan Police Department and the U.S. Justice Department agreed to a number of departmental reforms.
Since then, excessive use of force and shootings by police have remained relatively low. That might help explain why there was such little difference between police who wore body cams and those who didn't.
For now, this study leaves police and experts with a number of questions about the effectiveness of body cams, and whether they're worth the investment. The answer will likely vary from department to department.