The Seventh Juror(1962)

Original title: Le Septième Juré

In a moment of madness a middle-aged, married and respectable pharmacist kills a young woman who is sun-bathing by a lake. Unable to take in what he has done, he flees from the scene of the crime and behaves as if nothing has happened. Eventually her boyfriend is charged with the crime and, in a strange twist of fate, the killer finds himself serving on the jury.