This is only tangentially related, but there's a legal case that was discussed on Radiolab (the Buried Bodies case: http://www.radiolab.org/story/the_buried_bod

This is only tangentially related, but there's a legal case that was discussed on Radiolab (the Buried Bodies case: http://www.radiolab.org/story/the_buried_bodies_case/ http://www.radiolab.org/story/the_buried_bodies_case/) which you might find interesting. Essentially: A serial killer told his lawyers where two of his victims were buried. Should the lawyers disclose this information even though their defendant was the only source? It's interesting because it's not merely hypothetical, and their reporting is fairly good. While it doesn't answer your question, the spirit of the answer can maybe inform the spirit of how one would answer your question.