Claims for alleged breach of fiduciary duty proceeded past summary judgment motions in Vaxiion Therapeutics v. Foley & Lardner, 3-07-CV-280 (S.D. Cal., Dec. 4, 2008).  A subject-matter conflict, or technology conflict, was alleged based on patent attorneys in the firm’s San Diego and D.C. offices filing applications for separate companies, both claiming “minicell” technologies.  The provoking cause of the suit was that continuity was maintained between the provisional and utility filing dates for one Vaxiion application, but the PCT filing was a day late. In that period where priority could have been claimed, an application was filed on behalf of Vaxiion’s competitor, EnGeneIC. Vaxiion discharged the San Diego attorneys, but the firm’s D.C. office continued to prosecute the later-filed EnGeneICapplication, including efforts to swear behind the Vaxiion disclosure. In a civil case based on common-law, fiduciary standards as well as professional conduct standards for patent attorneys, a host of possibilities are presented.  The Court held that the proper cause of action in California is for breach of fiduciary duty, and it notes variations between the elements of proof under California law and that of other states.  For example, it did not need to be shown that attorneys in the San Diego office had communicated client confidences to their colleague in the D.C. office.  Also, while the Rules of Professional Conduct are not the basis for a tort claim, compliance vel non is probative evidence. But, what rules apply? Under the facts of the Vaxiion case, the possibilities are the California rules, e.g., 3-310(c)(2), or the D.C. rules, e.g., RPC 1.7(a), or the USPTO Code of Professional Responsibility, e.g., 37 C.F.R. 10.66(B).  Among those textually different rules, the standard can be that of an objective observer, or what subjectively an attorney understood, or perhaps, higher standards that a fiduciary must meet. What the USPTO rules call representation of clients with “differing interests,” or that the D.C. rules call a “concurrent conflict” that risks the representation being “materially limited,” would allow a wide range of evidence and expert opinion to be offered.  These subject-matter conflict cases also underscore the importance of conflict checks for technology as well as other types of potential conflicts.