That might be true in California, but it’s certainly not true for all states. About a year ago, there was a sad case in a small city in Virginia. A cop had shot an older lady in her car in a parking lot, then totally lied about the circumstances. (He eventually got a prison sentence.)
He had a history of being a violent drunk (was “allowed” to leave the Marines with an honorable discharge because of that), was in multiple accidents on the job while possibly drunk. He was only hired because his mother was a secretary to the police chief, and despite the better judgement of the psychologist who interviewed him.
Google Daniel Harmon-Wright for some disturbing reading about what is allowed to go on in small-town PDs.