Ok, random one, but...
it's a German film mainly set in a small catholic village/town in rural germany, about a serial killer psychopath and he's being interrogated/questioned by a german police officer throughout the film. The psychopath tells the police officer that he was training his son to be a killer. In the film, it features the police officer's son wetting the bed, setting fire to his sister's doll's house, and harming a baby lamb. Something about 3 traits of psychopathy.