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Ethics Opinion 337

Lawyer as Expert Witness

A lawyer serving as an expert witness to testify on behalf of a party does not thereby establish an attorney-client relationship with that party. Therefore, D.C. Rule 1.9 governing conflicts of interest with former clients would not apply to prohibit a lawyer from subsequently taking an adverse position to the party for whom the lawyer testified as an expert witness, even where the matter for which the lawyer testified and the matter involved in the subsequent representation are substantially related to one another. However, any firm that hires a lawyer as an expert witness should assure that the lawyer’s role as expert witness is made clear and should obtain the client’s informed consent if the expert’s role changes to that of co-counsel.

Applicable Rules

  • Rule 1.4 (“Communication”)
  • Rule 1.6 (“Confidentiality of Information”)
  • Rule 1.7 (“Conflict of Interest: General”)
  • Rule 1.9 (“Conflict of Interest: Former Client”)
  • Rule 1.10 (“Imputed Disqualification: General Rule”)
  • Rule 8.4 (“Misconduct”)


We have received an inquiry concerning the obligations of a lawyer who acts as an expert witness. The Inquirer is an attorney who has served as an expert witness in litigation involving bank regulatory and supervisory matters. She has been asked to provide expert testimony on behalf of an individual plaintiff who borrowed money from a savings bank that was placed in federal receivership and had its assets (including the loan at issue) sold to another financial institution. 

The defendant bank’s attorney has objected to the Inquirer’s serving as an expert witness because one or both of the law firms with whom the Inquirer was formerly employed did legal work for the defendant bank in prior years. For the purposes of this Opinion, we have been asked to assume that the D.C. Rules apply and that the prior representation of the defendant bank by the Inquirer’s former law firms involved neither the plaintiff in the current lawsuit (for whom the Inquirer wishes to testify) nor the plaintiff’s loan, which is the sole subject of the suit. The Inquirer has never worked on any previous matter for the defendant bank, and neither has the law firm with which she is currently employed.


A. A Lawyer Serving Solely as an Expert Witness Does Not Thereby Create an Attorney-Client Relationship 

A lawyer specializing in a particular legal subject may be engaged to serve as an expert witness who is expected to testify at a trial or hearing. As a general matter, a client-lawyer relationship can come into being as a result of reasonable expectations of the client and a failure of the lawyer to dispel these expectations. See D.C. Bar Ethics Op. 316 (2002) (recognizing that what conduct gives rise to an attorney-client relationship is one of substantive law in the relevant jurisdiction but that "[m]any courts look to the reasonable expectations and reliance of the putative client"); see also ABA Formal Op. 95-390 at 8. Clients can reasonably expect that lawyers whom they consult to perform legal services for them are bound by certain basic professional obligations, including the duties of confidentiality, see D.C. Rule 1.6, and the avoidance of conflicts of interest, see D.C. Rule 1.7. Effective February 1, 2007, a lawyer shall also be subject to the D.C. Rules of Professional Conduct with respect to the provision of "law-related services," which are defined as "services that might reasonably be performed in conjunction with and in substance are related to the provision of legal services." D.C. Rule 5.7(b) (eff. Feb. 1, 2007).

We believe, however, that if a lawyer serves solely as an expert witness on behalf of another law firm’s client,1 and the law firm explains this role to the client at the outset, then the expert witness would not typically have an attorney-client relationship with the party for whom she may be called to testify. A lawyer who is employed to testify about requirements of law or standards of legal practice, for example, acts like any non-lawyer expert witness. The expert provides evidence that lies within her special area of knowledge by reason of training and experience and has a duty to provide the court, on behalf of the other law firm and its client, truthful and accurate information. Towards this end, the lawyer serving as an expert witness may review selected discovery materials, suggest factual support for her expected testimony, and exchange legal authority applicable to her testimony with the law firm. The testifying expert also may help the law firm to define potential areas for further inquiry.

She nevertheless is presented as an objective witness and must even provide opinions adverse to the party for whom she expects to testify if frankness so dictates. A duty to advance a client’s objectives diligently through all lawful measures, which is inherent in a client-lawyer relationship, see D.C. Rule 1.3, is inconsistent with the role of an expert witness. Moreover, if an expert may testify at trial and her name has been provided to opposing counsel under procedural rules, she may be deposed by the opposing party. Communications between the expert and the retaining law firm or its client used by the expert in preparing her testimony ordinarily are discoverable.

The ABA has issued an opinion consistent with this conclusion. See ABA Formal Op. 97-407. Similarly, most state bar ethics committees that have considered the issue have rendered opinions that support the conclusion that a lawyer employed as an expert witness does not form a client-lawyer relationship with the party for whom she is engaged to testify. See, e.g., Virginia State Bar Ethics Op. 1884 (1989) (noting that if an attorney serves purely as an expert witness, the Code of Professional Responsibility is inapplicable and does not preclude service as an expert witness on different issues for both parties of an action); State Bar of S.D., Ethics Comm. Op. 91-22 (1992) (lawyer serving as expert witness for insurance company A defending a bad faith claim brought by insurance company B may represent an insured of insurance company B in an unrelated claim against a third party, in part because insurance company A is not the expert witness’s client); Phila. (Pa.) Bar Ass’n, Prof. Guidance Comm. Op. 88-34 (1988) (it is permissible under Pennsylvania’s Rules for a lawyer to serve as an expert witness for a party while at the same time serving as an expert witness for the party’s opponent in another unrelated suit).

D.C. Rule 1.9 states that “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 consents after consultation.” Id. As we have already discussed, a client-lawyer relationship will not exist by virtue of the Inquirer’s serving as an expert witness. Therefore, Rule 1.9 is not triggered by this Inquiry.2

B. Clarifying the Lawyer/Expert’s Role

The law firm that hires a lawyer as an expert witness should take care to avoid confusion in the mind of its client as to the different role a lawyer plays as an expert witness. In order to avoid any misunderstanding about whether a client-lawyer relationship is created, the law firm should make the expert’s role clear at the outset of the engagement - for example, through a written engagement letter defining the relationship, including its scope and limitations, and the responsibilities of the expert witness. It is also the responsibility of the law firm that has engaged the expert witness to assure that its client is fully informed as to the nature of the expert’s role, see D.C. Rule 1.4, especially because any communications between the client and lawyer expert are likely to be discoverable.3

In actual practice, the distinction between the role of a lawyer acting as an expert witness and a lawyer acting in a representational capacity can become blurred. The simplest situation, which we have already discussed above, is when the lawyer is hired as an expert witness and the lawyer expert forms no attorney-client relationship with either the hiring law firm or the law firm’s client.

A more complicated situation can arise when a lawyer serving as co-counsel in the case becomes an expert witness. Under this scenario, the Rules of Professional Conduct clearly apply, and the client needs to provide informed consent to the lawyer’s changing roles. For example, if a lawyer in the case becomes an expert witness, the client needs to understand that whatever confidences and secrets may have been revealed to the lawyer may be subject to discovery now that the lawyer has become a witness. D.C. Rule 1.6(e)(1) requires a client’s informed consent before any such confidences or secretes may be used or revealed.

A third scenario – where a lawyer originally hired as an expert witness is asked to become a consultant or co-counsel on a different aspect of the case – raises some additional complications. Where an expert witness morphs into a co-counsel role, the expert witness must exercise special care to assure that the law firm and the client are fully informed and expressly consent to the lawyer’s continuing to serve as an expert witness with respect to some issues in the case. See D.C. Rule 1.2(c) (stating that a “lawyer may limit the objectives of the representation if the client consents after consultation.”) The lawyer serving as a consultant or co-counsel is clearly bound by the D.C. Rules of Professional Conduct relating to conflicts of interest and imputed disqualification with respect to such service.

C. Additional Considerations

Even though the lawyer’s role as an expert witness does not form a client-lawyer relationship with the party on whose behalf she is to be called, the lawyer who serves as an expert witness is still subject to the D.C. Rules of Professional Conduct that govern lawyers generally. For example, were the expert witness to testify falsely, discipline under D.C. Rule 8.4 would be warranted. See generally ABA Formal Op. 336 (1974); ABA Formal Op. 97-407.

Moreover, D.C. Rule 1.7(b)(4) may impose certain limitations upon the lawyer and her law firm as a result of her serving as an expert witness. For example, if she were asked to represent a client in a matter adverse to the party for whom she currently is serving as an expert, her responsibilities to that party, as well as her own financial, business, or personal interests might preclude the representation altogether.4 And if she were asked to represent a client after the conclusion of her service as an expert witness, she might be bound by a confidentiality agreement with the party for whom she testified that could preclude her from zealously representing the new client. See D.C. Rule 1.7(c)(2) (eff. Feb. 1, 2007) (even with the client’s informed consent, a lawyer may only represent a client if she “reasonably believes that [she] will be able to provide competent and diligent representation to each affected client”).

Approved: December 19, 2006
Published: February 2007


1. This question is distinct from a consultant providing expert legal advice to a firm and/or its client. A legal consultant may act as a lawyer representing the client, rather than as a witness. The lawyer as expert consultant may act in the role of co-counsel in the matter as to the area upon which she is consulted and as such is subject to all of the D.C. Rules of Professional Conduct. There are a wide variety of circumstances in which a lawyer acts as a consultant and may thereby be undertaking a representation. See also D.C. Rule 1.6(e)(6) (eff. Feb. 1, 2007) (permitting a lawyer who consults with another lawyer to use or reveal client confidences and secrets “to the extent reasonably necessary to secure legal advice”).
2. We note that, even if the Inquirer’s serving as an expert witness on behalf of a particular party constituted a “representation” of that party sufficient to trigger the obligations of D.C. Rule 1.9, neither she nor her new law firm would be disqualified under the facts as presented here. The Inquirer never personally represented the defendant bank while working at her prior law firms, and her new firm has never represented the defendant bank. Because the defendant bank is not a client “about whom the [Inquirer] has in fact acquired information protected by Rule 1.6 that is material to the matter,” there is no conflict of interest that would be imputed to the new law firm. See D.C. Rule 1.10(b).
3. In 1993, Fed. R. Civ. P. 26 was amended to make information “considered” by an expert witness discoverable (previously, it was a narrower “reliance” standard). The comments to this amendment state that its disclosure requirements were intended to overcome privilege claims, and every federal court to decide the issue has so held. See Fidelity Nat’l Title Ins. Co. v. Intercountry Nat’l Title Ins. Co., 412 F.3d 745 (7th Cir. 2005); In re Pioneer Hi-Bred Int’l, Inc., 238 F.3d 1370 (Fed. Cir. 2001). Therefore, the traditional protection afforded by the opinion work product and attorney-client privileges has largely given way to a policy favoring mandatory disclosure of information provided to expert witnesses.
4. If the conflict arises only under Rule 1.7(b)(4), then the revised Rules would not necessarily impute that disqualification to her entire firm. See D.C. Rule 1.10(a)(1) (eff. Feb. 1, 2007). Just because a lawyer serving as an expert might have a financial, business, property or personal interest in a particular party does not always mean that her entire firm would thereby be precluded from representing a client adverse to that party.