“Cops being investigated by other cops are almost never found to be guilty of any wrong doing. “
You mean like that recent story of the cop who crossed the center line and killed two bicyclists? His fellow cops allowed him to leave the scene without testing him to see if he was drunk.
It happens much, perhaps most of the time. LEO’s tend to not only think they are above the law, often they believe they ARE the law. Given that usually they can get away with breaking the law, one has to wonder if they are not right. It's one of the reasons more and more people don't go anywhere without a video or audio recorder. It's a small measure of insurance against police abuse of power.