Deliberate mistake: 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 - I repeat: never - in exactly the same order as in English. Words that actually belong together can be placed on opposite ends of a sentence.
New York Detective: Is says here she tried to kill you at an - exercise class?
Alex Bernier: She tried to kill me at an exorCISM.