A former Frankfurt deputy police chief has been found guilty of ordering an officer to threaten violence against a suspected child kidnapper.
Wolfgang Daschner said he wanted to save the missing boy
Wolfgang Daschner had claimed he had acted to help find 11-year-old Jacob von Metzler, who was later found dead.
Daschner, 61, must pay a fine of 10,800 euro (£7,400) if he breaks his sentence of one year's probation for inducing misuse of authority and coercion.
The kidnapper, Magnus Gaefgen, is serving life for the boy's murder.
The unnamed senior officer who Daschner ordered to use "direct force" on Gaefgen was fined 3,600 euros (£2,473), also subject to a year's probation.
Judge Baerbel Stock said she had handed down the lightest possible sentence because the officers had the "honourable motive of saving a life".
"But it must also be made clear that the laws have to be followed, including when one is in difficult situations," she said.
The case has led to debate among Germans about whether such means might be legitimately used in some cases, and Daschner had widespread public sympathy.
Last year, he admitted threatening to use torture against the man, but his defence was that the circumstances justified his actions.
The events took place two years ago when the police were trying to determine the whereabouts of the German banker's son.
Gaefgen, despite hours of questioning, refused to speak.
Daschner said he had hoped to find the boy alive, but he had in fact already been killed.
The head of Germany's GDP police trade union, Konrad Freiburg, welcomed Monday's ruling.
"The verdict protects the security rights of police while taking into account the extremely difficult situation for the accused," he said in a statement.
He added that the ruling made it clear to the public that force, or the threat of force, is not permitted against people who are held in custody.