In the case styled Kennedy v. MindPrint, the Fifth Circuit gave a bone to lawyers who leave their big firm dreams and find themselves representing a client with interests adverse to a big firm client. Kirk Kennedy was an associate in Jackson Walker's bankruptcy section for a relatively short period of time, but during that time one of the firm's partners represented a client named MindPrint in bankruptcy court. Though Kennedy worked with this partner, he never became aware of the firm's representation of MindPrint and was never privy to any of MindPrint's confidential information.
He subsequently left the firm and found himself representing a physician who was involved in an adversary proceeding in the MindPrint bankruptcy case. Jackson Walker moved to disqualify him from representing the good doctor, arguing that there was an irrebuttable that he had learned MindPrint's confidential information while at the firm. The district court granted the motion.
Kennedy appealed and the Fifth Circuit had to decide whether he was disqualified from representing his new client because of Jackson Walker's representation of MindPrint. After examining the Texas Disciplinary Code of Professional Conduct, the Model Rules of Professional Conduct, and some fancy law review articles, the Fifth Circuit decided that an irrebuttable presumption was "both unworkable and unworkable." It held, instead, that a migrating lawyer like Kennedy should have the opportunity to demonstrate that he didn't obtain confidential information of his former firm's client while working at the big firm (the court passed on the question of whether the firm or the migrating lawyer bears the burden of proof).
A copy of the opinion is here: MindPrint Case.