The trial court has inherent power "to control in furtherance of justice, the conduct of its ministerial officers, and of all other persons in any manner connected with a judicial proceeding before it, in every matter pertaining thereto." ( 128, subd. (a)(5).) This inherent power includes authority to disqualify an attorney who violates California's ethics rules. (People ex rel. Dept. of Corporations v. SpeeDee Oil Change Systems, Inc. (1999) 20 Cal.4th 1135, 1145 86 Cal. Rptr. 2d 816, 980 P.2d 371.) "Determining whether a conflict of interest requires disqualification involves more than just the interests of the parties. ... Ultimately, disqualification motions involve a conflict between the clients' right to counsel of their choice and the need to maintain ethical standards of professional responsibility. The paramount concern must be to preserve public trust in the scrupulous administration of justice and the integrity of the bar. The important right to counsel of one's choice must yield to ethical considerations that affect the fundamental principles of our judicial process. " (Id. at pp. 1145-1146.) The State Bar Rules of Professional Conduct provide that an attorney "shall not, without the 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." (Rules Prof. Conduct, rule 3-310(E).) An attorney risks violating rule 3-310(E) in two different scenarios: "(1) in cases of successive representation, where an attorney seeks to represent a client with interests that are potentially adverse to a former client of the attorney; and (2) in cases of simultaneous representation, where an attorney seeks to represent in a single action multiple parties with potentially adverse interests." (In re Charlisse C. (2008) 45 Cal.4th 145, 159 84 Cal. Rptr. 3d 597, 194 P.3d 330.) "Case law has developed different standards for attorney disqualification depending on whether the conflict arises out of successive representation or simultaneous representation." (Montgomery v. Superior Court (2010) 186 Cal.App.4th 1051, 1055 112 Cal. Rptr. 3d 642 (Montgomery).) Where an actual conflict of interest stems from simultaneous adverse representation, the rule almost automatically requires disqualification "'regardless of whether the simultaneous representations have anything in common or present any risk that confidences obtained in one matter would be used in the other. ' " (In re Charlisse C., supra, 45 Cal.4th at p. 160.) Where the conflict "is one that arises from the successive representation of clients with potentially adverse interests ... the governing test requires that the client demonstrate a 'substantial relationship' between the subjects of the antecedent and current representations." (Flatt v. Superior Court (1994) 9 Cal.4th 275, 283 36 Cal. Rptr. 2d 537, 885 P.2d 950 (Flatt).) "A 'substantial relationship' exists whenever the 'subjects' of the prior and the current representations are linked in some rational manner." (Jessen v. Hartford Casualty Ins. Co. (2003) 111 Cal.App.4th 698, 711 3 Cal. Rptr. 3d 877.) "The 'substantial relationship' test mediates between two interests that are in tension in such a context--the freedom of the subsequent client to counsel of choice, on the one hand, and the interest of the former client in ensuring the permanent confidentiality of matters disclosed to the attorney in the course of the prior representation, on the other." (Flatt, supra, at p. 283.) "When a substantial relationship has been shown to exist between the former representation and the current representation, and when it appears by virtue of the nature of the former representation or the relationship of the attorney to his former client confidential information material to the current dispute would normally have been imparted to the attorney ... , the attorney's knowledge of confidential information is presumed." (Global Van Lines, Inc. v. Superior Court (1983) 144 Cal.App.3d 483, 489 192 Cal. Rptr. 609.) In such cases, disqualification of the attorney's representation of the second client is mandatory. (Flatt, supra, at p. 283.)