I'm thinking that isn't the only way to train a police dog. Sounds very abusive to me.
Different dogs needs different disciplines. My dog, "Rose" (Husky/GS x BC) startles easily and will NOT respond to being smacked. We isolate her to the basement while my other dog and I "play" outside. She gets that message first time, every time.
Pyg (Lab/GS x Pitbull) understands if she really goofs up and I smack her on her rump.