"Public Prosecutor" was the first TV series made on film. After a few episodes, the series was picked up by the Dumont Network and according to IMDB, it was padded to fit a 30 minute time slot by adding a panel to discuss who might be responsible for the crime in the show. The version I saw of "The Case of the Devil's Heart" is one of the early versions...without the panel.
The Prosecutor (John Howard) investigates the death of a young man who, along with his seemingly brain-addled sister, are heirs to a fortune. While the case seems like an accidental death, slowly it appears as if there is some other explanation for the death...and the clues are mighty tenuous and strange and involve nursery rhymes.
The resolution to the crime involves connecting the dots in a way that simply seemed irrational...and a bit silly. I'll have to watch a few more episodes to see if they're as bad as this one! Hopefully they are not.