I agree with you, but isn't this more of a problem with the implementation of body cameras, rather than the idea itself? Normally these sorts of places create bureaucratic systems to enforce common practise and a set of standards, which can be easily circumnavigated if you know the right people. I don't see why the police department can't create a system which requires police to have functioning body cameras, and use software and hardware to enforce it properly, rather than just relying on trust.