Under the lawyer-witness rule (or, the “advocate-witness rule”), lawyers generally are believed to be disqualified from representing clients in cases where lawyers may be called to testify as fact witnesses.

One of the primary justifications for this rule is to prevent jury confusion over the separate roles of an advocate and a witness.  The reasoning is that combining the roles of advocate and witness has the potential to prejudice the opposing party because a jury may be unclear whether an attorney asked to testify is making a statement that should be taken as proof or as an analysis of the proof.

Reference Desk

F.D.I.C. v. Fire Ins. Co., 50 F.3d 1304 (5th Cir. 1995):

The proscription against an attorney serving as both an advocate and a witness in the same litigation is a long-standing ethical rule. Its origin may be traced to the common law principle of evidence that neither a party nor his agent is competent as a witness on the party’s behalf. During the nineteenth century, the prohibition against lawyer-witnesses became a matter of professional ethics. Bar associations in the United States included the rule among their earliest standards of professional behavior. Over the years, various reasons have been offered for an ethical prohibition against advocates testifying. The Model Code proposes four justifications for the rule: (1) the lawyer may be a less effective witness because he is more easily impeachable for interest; (2) opposing counsel may be inhibited in challenging the credibility of a lawyer who also appears as an advocate; (3) a lawyer-witness must argue his own credibility; and (4), while the role of a witness is to objectively relate facts, the role of an advocate is to advance his client’s cause. Another rationale commonly advanced for the rule focuses on the appearance of impropriety that may be created when a lawyer testifies on behalf of his client. For one or more of the foregoing reasons, the general prohibition against the lawyer-witness remains a prescript reiterated in many contemporary ethical canons.

In American Airlines, 972 F.2d at 605, we made clear that “disqualification cases are governed by state and national ethical standards adopted by the court.” Id. at 610. At least four separate ethical canons are relevant to a review of the district court’s order to disqualify counsel in the instant case. Each of these different sets of rules specifically addresses the issue of a lawyer serving as witness.  As authorized by 28 U.S.C. § 2071, district courts such as the Northern District of Texas may adopt rules for the conduct of attorneys. The local rules promulgated by the local court itself are the most immediate source of guidance for a district court.  Therefore, the Local Rules of the United States District Court for the Northern District of Texas (“Northern District Rules”), are not irrelevant to our inquiry.[10] Nonetheless, parties cannot be deprived of the right to counsel of their choice on the basis of local rules alone. Dresser, 972 F.2d at 543. Local rules are not the “sole” authority governing motions to disqualify counsel. Motions to disqualify are substantive motions. Therefore, they are decided under federal law. When reviewing the disqualification of an attorney, we must “consider the motion governed by the ethical rules announced by the national profession in the light of the public interest and the litigant’s rights.” Id. The norms embodied in the Model Rules and the Model Code are relevant to our inquiry, “as the national standards utilized by this circuit in ruling on disqualification motions.” American Airlines, 972 F.2d at 610. Additionally, consideration of the Texas Rules is also necessary, because they govern attorneys practicing in Texas generally, and because the Northern District Rules contain language virtually identical to the state canon. By consulting these four sets of governing rules, we must weigh the need for disqualification of the FDIC’s counsel in reference to the relevant affirmative defenses raised by U.S. Fire. Unfortunately, the rules do not enunciate a common standard. The Northern District Rules, the Texas Rules, the Model Rules, and the Model Code delineate dissimilar, arguably contradictory, rules for dealing with lawyer-witnesses. Therefore, we must weigh the relative merits of each of the various competing disqualification rules as we proceed through each successive step of our analysis.

People v. Donaldson, 93 Cal.App.4th 916 (2001):

Occasionally a lawyer is called upon to decide in a particular case whether he will be a witness or an advocate.  If a lawyer is both counsel and witness, he becomes more easily impeachable for interest and thus may be a less effective witness.  Conversely, the opposing counsel may be handicapped in challenging the credibility of the lawyer when the lawyer also appears as an advocate in the case.  An advocate who becomes a witness is in the unseemly and ineffective position of arguing his own credibility.  The roles of an advocate and of a witness are inconsistent; the function of an advocate is to advance or argue the cause of another, while that of a witness is to state facts objectively.

California Rules of Professional Conduct, Rule 3.7 (Lawyer as Witness):

(a) A lawyer shall not act as an advocate in a trial in which the lawyer is likely to be a witness unless:

(1) the lawyer’s testimony relates to an uncontested issue or matter;
(2) the lawyer’s testimony relates to the nature and value of legal services rendered in the case; or
(3) the lawyer has obtained informed written consent from the client. If the lawyer represents the People or a governmental entity, the consent shall be obtained from the head of the office or a designee of the head of the office by which the lawyer is employed.

(b) A lawyer may act as advocate in a trial in which another lawyer in the lawyer’s firm* is likely to be called as a witness unless precluded from doing so by rule 1.7 or rule 1.9.