POLICING: The body cam revolution: What it has, and hasn’t, accomplished.

The cameras have put a lens on a job that’s already fraught, difficult, and often thankless. And some say it is all for naught. Indeed, studies show the body camera revolution hasn’t curbed police shootings of unarmed Americans, nor has it led to more prosecutions of police officers for misconduct.

Yet the cameras, veteran police monitors say, have nevertheless had profound and often positive impacts on policing, if in subtle ways. For officers, they have become important backup in a video era when controversial arrests go viral. And for a public demanding answers about police shootings of Americans, particularly people of color, they provide fact-studded narratives that, while rarely complete, offer a way forward.

And they have provided crucial evidence in a few egregious cases of law enforcement misconduct.

They’re sources of evidence. And evidence is not always determinative in and of itself.