This week, we saw compelling evidence of how a body camera on a police officer worked and, at the same time, how it did not.
By now you've seen the simple traffic stop in Cincinnati, where the benign turn ugly and then deadly. Officer Ray Tensing not only shot Sam Dubose in the head over a missing license plate, but lied to superiors about being dragged by the moving car, fearing for his life.
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Because the camera Tensing wore documented otherwise, he is now indicted for murder.
But the bigger issue may be that the body camera did nothing to stop the shooting death of another person of color.
The officer was well-aware his words and actions were being recorded, an awareness that experts say should alter the way officers decide to act. But this time it didn't.
That stop in Cincinnati is a clear indication -- the body cameras that have been promoted as a breakthrough method in holding officers accountable are not a cure-all at all. Still, that doesn't discount their ability to be critical tools.
Sam Dubose, Michael Brown, Eric Garner, Freddie Gray, Walter Scott and Sandra Bland are names that have become hashtags in the furious and frustrated call for policing reform only because there were people with cameras there to record what happened in their encounters with police.
The statistics behind the nationwide push for police body cameras are hard to ignore -- significant drops in use-of-force and in citizen complaints. Body cameras are good for good officers and bad news for bad officers.
Body cameras do and will play a critical role in criminal justice, and police departments are right to fund and deploy them. But this week we are reminded that the focus of good policing should be on the people wearing them.
Follow Glenna Milberg on Twitter @GlennaOn10