Heath Ledger, Shannyn Sossamon, Mark Addy, and Leagh Conwell all previously appeared together in A Knight's Tale (2001). Both movies written and directed by Brian Helgeland.
Originally scheduled for January 17, 2002, the film's release date was postponed when the visual effects had to be redone because they were thought to be unintentionally funny. According to a anonymous source close to the production quoted by Variety magazine, the special effects depicting sins exiting the human body after death looked like "calamari".
According to Brian Helgeland, Peter Weller did extensive research for his role by studying old religious rituals and histrionics.
Leagh Conwell also portrayed Heath Ledger's younger self in A Knight's Tale.
There is one scene in the movie where Heath Ledger reads a Latin sentence in a book. As he is translating the sentence, he goes over the words one by one with his finger. This would never be possible in a Latin sentence, because words in Latin are never in exactly the same order as in English. Words that actually belong together can be placed at opposite ends of a sentence.