Character mistake: At the end, when Mitch tells Agent Tarrance that the government can convict the law firm on mail fraud and racketeering, he says he got the idea while he was studying for the bar exam. He actually got the idea from a client earlier in the film when the client was complaining about being over-billed and tells Mitch that every time a bill is mailed through USPS, the firm is committing mail fraud which is a federal offense, punishable by fines and prison.
Character mistake: After learning of the firm's conspiracy, Mitch is worried about violating attorney/client privilege in order to expose it. Since Mitch knows that a crime is being committed (e.g. mailing the overcharged bills through the Post Office), attorney/client privilege doesn't apply.