I've never seen that but I have personally witnessed a policeman punch a man in the face for no apparent reason, he got let off by the court.
I love how corrupt society is.
Police go on power-trips, most of them abuse their power. There was an article I read about a year and a half ago, it was about an Oklahoma cop beat the hell out of a suspect in a murder case where the Oklahoma's cop's partner was murdered. There were more then two police officers that watched this crime take place.