The title, "A Perfect Murder", is a quote from the 1954 Hitchcock version of this story, "Dial M For Murder". See Memorable Quotes from "Dial M For Murder".
To calm her and create a certain atmosphere of intimacy before filming the lovemaking scenes, Viggo Mortensen sang a couple of love songs to Gwyneth Paltrow that he learned in Argentina when he was young. In an interview he said, "I don't know if that ended up scaring her instead."