Conflict of interest

California State Bar Formal Opinion No. 1980-52 It is improper for counsel in a criminal case to represent a defendant where a previous client of that attorney's office is a witness against the new client and it is reasonably foreseeable that the confidences or secrets of the former client may be, or may reasonably appear to the client to be, used. http://www.calbar.ca.gov/Portals/0/documents/ethics/Opinions/1980-52.htm

California State Bar Fomral Opinion No. 1981-59 "It is improper for counsel to continue representing either defendant charged in two separate, unrelated criminal cases once counsel becomes aware that one of these defendants is attempting to become, or has become, an undercover informant against the other defendant." http://www.calbar.ca.gov/Portals/0/documents/ethics/Opinions/1981-59.htm