Search for Jakob Von Metzler (I am on mobile). It's a case of a boy kidnapping. The kidnapper was caught, didn't want to tell the officers where he hid the kid. So one of the officers threatened him with pain. He told them and they found the kid (already dead). Kidnapper got sent to jail. The crazy part? The officer was charged because he threatened the kidnapper with pain if he didn't tell them. Will that ever happen in the US? Nope
Are you saying it was wrong for charges to be brought because of the threat? It should have been disregarded because it involved a child kidnapping? What if the police had the wrong man, is it still ok to threaten?
What if it wasnt a child kidnapping but some other crime? Still ok to threaten? Slippy slope there isnt it. As i understand from Wikipedia Germany got a human rights caution and he was awarded 3k for emotional damages.