The downside of having each cop wear a camera is how long does the cop shop have to retain the video records? The storage costs will start to cost the agency real money. A local (Missouri) police force stopped using the cameras when FOI petitioners started asking for everything and then posting the amusing ones on YouTube. One or two full-time employees were required to just process the FOI requests. This was in a small town. A jurisdiction like DC might reqiire a small beaurocracy to do the same thing.
I don’t know what the answer is, but every cop’s every day being considered pubic record is a can of worms.
If I were on a jury and there was supposed to be video available, and it was not, I would take anything said by the police with a healthy dose of skepticism.
If all the police had in such a case was the word of the cop, the defendant would walk.