My local police department isn't really all that trustworthy. They've been caught doing bad things including a nasty incident where they massively screwed up with a disabled person. There were no consequences to the misbehaving officers involved.
On the other hand, I have relatives in another police department (not local to me), and that police department is trustworthy because they severely punish and actually fire police officers for bad behavior.
The difference is the leadership. The sad reality is that quite a lot of police departments in the US (e.g. clearly the Minneapolis PD) have very bad leadership who lets bad behavior go unpunished, and the officers behave poorly in lots of circumstances.