by Michael D. Stewart

Your good client calls with a new case. It will be hotly contested, the fees could reach seven figures, and your client wants to make sure you have the bandwidth. You just settled another case, you ran a conflict search, and the adverse party has never hired your firm. Full speed ahead. A few months into the case, you receive a letter from opposing counsel contending you have a conflict of interest. They claim one of your firm’s other offices (across the country) recently hired a mid-level transactional associate who represented the adverse party while at their prior firm. Although you have never heard of—much less communicated with—the associate, your adversary claims the associate’s prior work for the adverse party was substantially related to the current litigation matter and demands that you and your firm withdraw from the case.

Is your adversary right? Will you have to tell your client you need to withdraw or face a disqualification motion? Will the judge make you do so? The clearest answer is: Maybe.

The rules governing duties lawyers owe to former clients were revised and clarified in 2018 when the California Supreme Court approved the current California Rules of Professional Conduct (CRPC). “A lawyer who has formerly represented a client in a matter shall not thereafter represent another person in the same or a substantially related matter in which that person’s interests are materially adverse to the interests of the former client unless the former client gives informed written consent.” CRPC Rule 1.9(a). Similarly, a lawyer moving to a new firm cannot represent a client of the new firm against a client represented by their former firm if the current matter and the prior matter are the same or substantially related. CRPC Rule 9.1(b). The lawyers in the new firm are also precluded from the representation if, as discussed below, the newly hired lawyer’s conflict of interest is imputed to the rest of their new firm.

What does “substantially related” mean?
A great deal turns on whether the earlier matter is “substantially related” to the proposed matter. The comments to Rule 1.9 of the CRPC are instructive. They begin by framing the two key duties owed to a former client: “After termination of a lawyer-client relationship, the lawyer owes two duties to a former client. The lawyer may not (i) do anything that will injuriously affect the former client in any matter in which the lawyer represented the former client, or (ii) at any time use against the former client knowledge or information acquired by virtue of the previous relationship. [Citations omitted.]” CRPC Rule 1.9, cmt. 1.

The same comment goes on to give examples of “substantially related”: “(i) a lawyer could not properly seek to rescind on behalf of a new client a contract drafted on behalf of the former client and (ii) a lawyer who has prosecuted an accused person could not represent the accused in a subsequent civil action against the government concerning the same matter. [Citations omitted.]” Id.

Comment 3 to CRPC Rule 1.9 expands on those examples, stating: “Two matters are ‘the same or substantially related’ for purposes of this rule if they involve a substantial risk of a violation of one of the two duties to a former client described above in Comment [1]. For example, this will occur: (i) if the matters involve the same transaction or legal dispute or other work performed by the lawyer for the former client; or (ii) if the lawyer normally would have obtained information in the prior representation that is” confidential or protected by the attorney-client privilege and “the lawyer would be expected to use or disclose that information in the subsequent representation because it is material to the subsequent representation.”

With respect to the hypothetical posited above, the first analysis is whether the matter worked on by your firm’s recently hired transactional associate is the same as or (more likely) substantially related to the litigation case you have been working on for the last few months. As is frequently the case, you and opposing counsel may reach differing conclusions. You may be able to reach a compromise, such as ethically screening the new associate (discussed below), or you may not. Ultimately, a judge or other arbiter may have to make the final decision (a topic which, although often fascinating and always consequential, exceeds the scope of this article).

Can others in the firm represent the client if the tainted lawyer is ethically screened?
Generally speaking, before the adoption of CRPC Rule 1.9, California’s rule was that one lawyer’s knowledge of a former client’s confidential information was imputed to the entire firm. Hence, if the lawyer was subject to disqualification, so too was the entire firm. In one well-reasoned case, the California Court of Appeal blessed the law firm’s use of an ethical screen of the tainted lawyer to avoid the remedy of disqualification. See Kirk v. First Am. Title Ins. Co., 183 Cal. App. 4th 776, 784 (2010) (presumption of imputed conflict was rebuttable where law firm adequately screened the lawyer from others at the firm who represented the adverse party against the tainted lawyer’s former client).

With the adoption of CRPC Rule 1.10 in 2018, a law firm can avoid the imputed knowledge of a tainted lawyer (and hence disqualification of the entire firm) provided the lawyer did not play a substantial role in the matter prior to joining the new firm, such lawyer is timely subjected to an ethical screen, and the aggrieved client is given proper written notice of the screen. CRPC Rule 1.10(a)(2).

The key question in determining if an ethical screen will cure the conflict of interest is whether “the prohibited lawyer . . . substantially participate[d] in the same or a substantially related matter.” CRPC Rule 1.10(a)(2)(i). Comment 1 to CRPC 1.10 sheds light on that standard, stating:

In determining whether a prohibited lawyer’s previous participation was substantial, a number of factors should be considered, such as the lawyer’s level of responsibility in the prior matter, the duration of the lawyer’s participation, the extent to which the lawyer advised or had personal contact with the former client, and the extent to which the lawyer was exposed to confidential information of the former client likely to be material in the current matter.

As a practical matter, the firm responding to the disqualification threat may seek evidence of the tainted attorney’s time entries and volume of time billed on the same or substantially related matter while at the prior firm. If the newly hired attorney does not have that information, the next step is to contact their prior firm, which is likely the one that is demanding your law firm’s withdrawal from the new matter. Therefore, obtaining and exchanging such information can be nuanced and triggers its own set of privilege issues. Ultimately, the parties may, through their lawyers, agree that the conflict of interest can be mitigated and possible motion practice avoided by screening the tainted lawyer.

If the tainted lawyer were to suddenly leave the firm, would that cure the imputation issue?
Putting aside the possible employment implications of such a sudden “departure,” the answer would be: No; not unless the associate had left the firm without divulging confidential information to those still at the firm. In Goldberg v. Warner/Chappell Music, Inc., 125 Cal. App. 4th 752 (2005), the tainted lawyer had left the firm three years before the firm was hired by the adverse party. The Goldberg court denied a motion to disqualify after finding that the tainted attorney had not provided confidential information to others at the firm. As explained in the Executive Summary to CRPC Rule 1.10, Goldberg’s holding is essentially codified in “Paragraph (b)” of Rule 1.10: “The concept recognized in Goldberg is that if a lawyer who has represented a client and acquired confidential information has left the firm, and no other lawyer who has acquired confidential information remains, then there is no one left in the firm with knowledge that can be imputed to other lawyers in the firm.”

Does the imputation doctrine make sense with increased lawyer mobility and the proliferation of larger firms?
One might argue that the Kirk case, although decided fifteen years ago, properly framed (and some might say answered) this question with a keen eye towards the future. As the court noted in Kirk:

The instant case illustrates the changing landscape of legal practice—we are concerned with the tainted attorney working in a different geographical office and in a different practice group from the attorneys with responsibility for the litigation. These are not attorneys discussing their cases regularly, passing each other in the hallways, or at risk of accidentally sharing client confidences at lunch. In a situation where the ‘everyday reality’ is no longer that all attorneys in the same law firm actually ‘work[] together,’ there would seem to be no place for a rule of law based on the premise that they do.”

183 Cal. App. 4th 776, 802.

There are, of course, rebuttals to that sentiment. Some might point to the fact that law firms now store immense amounts of readily searchable client data and client communications in their document management systems. Still, the situation encountered by the newly hired associate posited above is more common than one might think in the disqualification arena. As discussed below, lawyers are often prevented from joining a new law firm because of conflicts stemming from CRPC Rule 1.9 and the duties owed to former clients. But before addressing that issue, we should consider whether such conflicts of interest can be waived.

Can the aggrieved client waive the conflict?
Yes, both Rule 1.9(a) and (b) conclude by stating: “unless the former client gives informed written consent.” But is that likely to happen in the real world? Even if the former client were to give its lawyer an advance waiver, most such waivers do not include or even anticipate a situation where the lawyer could essentially switch sides and be adverse to the former client on the same or substantially related matter. Of course, in the hypothetical posed above, the potentially conflicted litigator and their law firm never represented the adverse party and would have had no opportunity to obtain a waiver of any sort.

Finally, at the risk of stating the obvious, the adverse party whose lawyer has sent you a disqualification demand is not likely going to waive the conflict—at least not after your firm has hired the associate. You may be able to convince the other side to not seek your disqualification—possibly by implementing an ethical screen—but the former client and their counsel can monitor the efficacy of the screen and will not likely give you informed written consent to proceed carte blanche.

Could you or your law firm have taken steps to avoid this situation?
Yes. There are alternatives the law firm could have explored, all of which rely on asking the prospective new hire the right questions and getting the right information.

First, the law firm could have obtained a list of all matters the associate had worked on and run those matters through the firm’s conflict database to ascertain possible conflicts of interest. But lawyers do not remember everything they might have worked on, and firms can only expect them to go back so many years. Problems can and do arise, despite the obligations associated with checking conflicts. See Robert K. Sall, The Art of Checking for Conflicts, Orange County Lawyer vol. 67, No. 4 at 61 (April 2025).

Second, if such a conflict search were performed and a conflict identified, the law firm could have inquired whether the associate “substantially participated” in the matter at their prior firm. Assuming the answer was no, the firm could hire the new associate and screen them from the litigation. But we lawyers often forget the extent of our involvement, especially in older matters. Many a law firm has hired a lawyer only to find that they worked on a possibly conflicting matter they unwittingly failed to identify to their new law firm.

Third, if a conflict search showed a possibly disqualifying matter, the law firm could ask opposing counsel to inquire if their client would waive the conflict to allow the associate to join the new law firm (where he or she would be promptly screened). This too raises issues. The associate often does not want to tell their current employer they are contemplating leaving the firm. Additionally, if the request is made and client refuses to waive the conflict, the associate is now possibly stuck at their current firm and viewed as a short-timer (or worse). Unlike the scenario above where the unwitting firm receives the disqualification threat after hiring the associate, there is little to no strategic reason for the client to refuse to waive the conflict to allow the associate to obtain new employment. Refusing to do so will almost certainly result in the law firm not hiring the associate. Any leverage associated with the disqualification threat will go away, leaving a disgruntled associate at a firm where neither side is particularly pleased with the other.

The bottom line is that not only can you risk withdrawal or disqualification by being adverse to a former client, you can suffer those same risks because of someone else’s former client. Fortunately, you can mitigate those risks by implementing appropriate hiring and conflict checking processes.

Michael D. Stewart is General Counsel of Sheppard, Mullin, Richter & Hampton LLP in Costa Mesa, California. He is also a member of the OCBA’s Professionalism & Ethics Committee. He can be reached at mstewart@sheppardmullin.com. The views expressed herein are his own.