One of the fundamentals of the german law systems was broken, by a well-meaning person for practically no gain. The kidnapper later sued the police for the torture and won.
Now germany doesn't have a fruit of the poisonous tree doctrine so the conviction for the kidnapping later was based partially on the information gained in that one interrogation, but what if the kidnapper would walk free because of such a breach of law?
[1] http://de.wikipedia.org/wiki/Entf%C3%BChrung_von_Jakob_von_M... (sorry, german only)