I believe theres some sort of dispensation when it comes to serial killers.
EF Benson wrote a cracking short ghost story on the subject called The Hanging of Alfred Wadham. The murderer confesses to a priest who has to officiate at the hanging of a wrongfully convicted man. The priest keeps his silence. Thereafter the priest is haunted by terrifying images of the innocent, but dead man.

Benson wrote the Mapp and Lucia stories, but that piece has a wonderful 1890's feel to it. Very decadent and florid - Wildean, like Dorian Gray. I believe when he was younger, Benson was on the edges of Reggie Turner/Wilde gay set. later in life he was the mayor of somewhere on on the south coast - Ryde, or somewhere like that.