What happens when police wear cameras isn't simply that tamper-proof recording devices provide an objective record of an encounter—though some of the reduction in complaints is apparently because of citizens declining to contest video evidence of their behavior—but a modification of the psychology of everyone involved. ...
In the U.K., where tests with them began in 2005, studies have shown that they aid in the prosecution of crimes, by providing additional, and uniquely compelling, evidence. In the U.S., in some instances they have shortened the amount of time required to investigate a shooting by police from two-to-three months to two-to-three days.
And they represent yet one more way we are being recorded by means that could eventually be leaked to the public.
--Christopher Mims, WSJ, on the effect of being watched