"It has long been held that under both Constitutions, a defendant is deprived of his or her constitutional right to the assistance of counsel in certain circumstances when, despite the physical presence of a defense attorney at trial, that attorney labored under a conflict of interest that compromised his or her loyalty to the defendant." (People v. Rundle (2008) 43 Cal.4th 76, 168.) A disqualifying conflict of interest may arise "in situations in which an attorney represents a defendant in a criminal matter and currently has or formerly had an attorney-client relationship with a person who is a witness in that matter. Such a conflict springs from the attorney's duty to provide effective assistance to the defendant facing trial and his fiduciary obligations to the witness with whom he has or had a professional relationship." (People v. Bonin (1989) 47 Cal.3d 808, 835.) To inquire into the effect of an alleged constitutional level conflict of interest, the court considers whether the defendant has shown both deficient performance by counsel, "and (2) a reasonable probability that, absent counsel's deficiencies, the result of the proceeding would have been different." (People v. Doolin (2009) 45 Cal.4th 390; Mickens v. Taylor (2002) 535 U.S. 162, 172-176; Strickland v. Washington (1984) 466 U.S. 668.) In Doolin, the Supreme Court outlined the appropriate inquiries in this context: "A determination of whether counsel's performance was 'adversely affected' under the federal standard 'requires an inquiry into whether counsel "pulled his punches," i.e., whether counsel failed to represent defendant as vigorously as he might have, had there been no conflict. In undertaking such an inquiry, we are . . . bound by the record. But where a conflict of interest causes an attorney not to do something, the record may not reflect such an omission. We must therefore examine the record to determine (i) whether arguments or actions omitted would likely have been made by counsel who did not have a conflict of interest, and (ii) whether there may have been a tactical reason (other than the asserted conflict of interest) that might have caused any such omission.'" (Doolin, supra, 45 Cal.4th at p. 418.) In Mickens, supra, 535 U.S. 162, 176, the U.S. Supreme Court clarified these distinctions: "'Breach of an ethical standard does not necessarily make out a denial of the Sixth Amendment guarantee of assistance of counsel.'" The variously imposed ethical duties of an attorney are equally important, but when a defendant seeks the application of an exclusionary rule for protecting a Sixth Amendment right to counsel, the defendant must show not just an ethical violation, but also that counsel was actively representing conflicting interests, and this prejudiced the defendant. (Ibid.; see Doolin, supra, 45 Cal.4th at p. 418.) Under rule 3-310(B)(1), an attorney may not accept or continue representation of a client without disclosure where "(1) The member has a legal, business, financial, professional, or personal relationship with a party or witness in the same matter." Under rule 3-310(E), an attorney shall not, without informed written consent of the client or former client, "accept employment adverse to the client or former client where, by reason of the representation of the client or former client, the member has obtained confidential information material to the employment." Under rule 3-700(B)(2), an attorney who represents a client in one matter shall withdraw from that employment, if the attorney "knows or should know that continued employment will result in violation of these rules."