Confessional

"Turns out by the time I stabbed Murphy you had already poisoned him, so I was let off with a warning."

"You're supposed to be the holy one, padre! What about Thou shalt not kill?"

"Technically speaking, I didn't. You did."

"But I'm safe because of the seal of confessional, right? You can't divulge anything I said while I was in here."

"Nary a word shall pass these lips, you may rest assured."

"Whew, that's a relief."

"You may, however, wish to take a moment to consult with the police sergeant standing outside with his ear pressed against the door."