Massachusetts Rules of Professional Conduct Rule 3.7: Lawyer as Witness
(a) A lawyer shall not act as advocate at a trial in which the lawyer is likely to be a necessary witness except where:
(1) the testimony relates to an uncontested issue;
(2) the testimony relates to the nature and value of legal services rendered in the case; or
(3) disqualification of the lawyer would work substantial hardship on the client.
Adopted June 9, 1997, effective January 1, 1998.
 Combining the roles of advocate and witness can prejudice the opposing party and can involve a conflict of interest between the lawyer and client.
 The opposing party has proper objection where the combination of roles may prejudice that party's rights in the litigation. A witness is required to testify on the basis of personal knowledge, while an advocate is expected to explain and comment on evidence given by others. It may not be clear whether a statement by an advocate-witness should be taken as proof or as an analysis of the proof.
 Paragraph (a)(1) recognizes that if the testimony will be uncontested, the ambiguities in the dual role are purely theoretical. Paragraph (a)(2) recognizes that where the testimony concerns the extent and value of legal services rendered in the action in which the testimony is offered, permitting the lawyers to testify avoids the need for a second trial with new counsel to resolve that issue. Moreover, in such a situation the judge has firsthand knowledge of the matter in issue; hence, there is less dependence on the adversary process to test the credibility of the testimony.
 Apart from these two exceptions, paragraph (a)(3) recognizes that a balancing is required between the interests of the client and those of the opposing party. Whether the opposing party is likely to suffer prejudice depends on the nature of the case, the importance and probable tenor of the lawyer's testimony, and the probability that the lawyer's testimony will conflict with that of other witnesses. Even if there is risk of such prejudice, in determining whether the lawyer should be disqualified, due regard must be given to the effect of disqualification on the lawyer's client. It is relevant that one or both parties could reasonably foresee that the lawyer would probably be a witness. The principle of imputed disqualification stated in Rule 1.10 has no application to this aspect of the problem.
 Whether the combination of roles involves an improper conflict of interest with respect to the client is determined by Rule 1.7 or 1.9. For example, if there is likely to be substantial conflict between the testimony of the client and that of the lawyer or a member of the lawyer's firm, the representation is improper. The problem can arise whether the lawyer is called as a witness on behalf of the client or is called by the opposing party. Determining whether or not such a conflict exists is primarily the responsibility of the lawyer involved. See Comment to Rule 1.7. If a lawyer who is a member of a firm may not act as both advocate and witness by reason of conflict of interest, Rule 1.10 disqualifies the firm also.
Corresponding ABA Model Rule. Identical to Model Rule 3.7.
Corresponding Former Massachusetts Rule. DR 5-101 (B), DR 5-102 (A).