Massachusetts Rules of Professional Conduct Rule 3.3: Candor Toward the Tribunal
(a) A lawyer shall not knowingly:
(1) make a false statement of material fact or law to a tribunal;
(2) fail to disclose a material fact to a tribunal when disclosure is necessary to avoid assisting a criminal or fraudulent act by the client, except as provided in Rule 3.3(e);
(3) fail to disclose to the tribunal legal authority in the controlling jurisdiction known to the lawyer to be directly adverse to the position of the client and not disclosed by opposing counsel; or
(4) offer evidence that the lawyer knows to be false, except as provided in Rule 3.3(e). If a lawyer has offered, or the lawyer's client or witnesses testifying on behalf of the client have given, material evidence and the lawyer comes to know of its falsity, the lawyer shall take reasonable remedial measures.
(b) The duties stated in paragraph (a) continue to the conclusion of the proceeding, including all appeals, and apply even if compliance requires disclosure of information otherwise protected by Rule 1.6.
(c) A lawyer may refuse to offer evidence that the lawyer reasonably believes is false.
(d) In an ex parte proceeding, a lawyer shall inform the tribunal of all material facts known to the lawyer which will enable the tribunal to make an informed decision, whether or not the facts are adverse.
(e) In a criminal case, defense counsel who knows that the defendant, the client, intends to testify falsely may not aid the client in constructing false testimony, and has a duty strongly to discourage the client from testifying falsely, advising that such a course is unlawful, will have substantial adverse consequences, and should not be followed. If a lawyer discovers this intention before accepting the representation of the client, the lawyer shall not accept the representation; if the lawyer discovers this intention before trial, the lawyer shall seek to withdraw from the representation, requesting any required permission. Disclosure of privileged or prejudicial information shall be made only to the extent necessary to effect the withdrawal. If disclosure of privileged or prejudicial information is necessary, the lawyer shall make an application to withdraw ex parte to a judge other than the judge who will preside at the trial and shall seek to be heard in camera and have the record of the proceeding, except for an order granting leave to withdraw, impounded. If the lawyer is unable to obtain the required permission to withdraw, the lawyer may not prevent the client from testifying. If a criminal trial has commenced and the lawyer discovers that the client intends to testify falsely at trial, the lawyer need not file a motion to withdraw from the case if the lawyer reasonably believes that seeking to withdraw will prejudice the client. If, during the client's testimony or after the client has testified, the lawyer knows that the client has testified falsely, the lawyer shall call upon the client to rectify the false testimony and, if the client refuses or is unable to do so, the lawyer shall not reveal the false testimony to the tribunal. In no event may the lawyer examine the client in such a manner as to elicit any testimony from the client the lawyer knows to be false, and the lawyer shall not argue the probative value of the false testimony in closing argument or in any other proceedings, including appeals.
Adopted June 9, 1997, effective January 1, 1998.
 The advocate's task is to present the client's case with persuasive force. Performance of that duty while maintaining confidences of the client is qualified by the advocate's duty of candor to the tribunal. However, an advocate does not vouch for the evidence submitted in a cause; the tribunal is responsible for assessing its probative value.
Representations by a Lawyer
 An advocate is responsible for pleadings and other documents prepared for litigation, but is usually not required to have personal knowledge of matters asserted therein, for litigation documents ordinarily present assertions by the client, or by someone on the client's behalf, and not assertions by the lawyer. Compare Rule 3.1. However, an assertion purporting to be on the lawyer's own knowledge, as in an affidavit by the lawyer or in a statement in open court, may properly be made only when the lawyer knows the assertion is true or believes it to be true on the basis of a reasonably diligent inquiry. There are circumstances where failure to make a disclosure is the equivalent of an affirmative misrepresentation. The obligation prescribed in Rule 1.2(d) not to counsel a client to commit, or assist the client in committing, a fraud applies in litigation. Regarding compliance with Rule 1.2(d), see the Comment to that Rule. See also the Comment to Rule 8.4(b).
Special Meaning of "Assistance"
[2A] Comment 3 to Rule 4.1 states the general rule that the word "assisting" refers to that level of assistance that would render a third party liable for another's crime or fraud, i.e., assistance sufficient to render one liable as an aider or abettor under criminal law or as a joint tortfeasor under principles of tort and agency law. However, the concept of assisting has a special meaning in Rule 3.3 because it deals with a lawyer's conduct before a tribunal. The term assisting in Rule 3.3 is not limited to conduct that makes the lawyer liable as an aider, abettor or joint tortfeasor. Rule 3.3(a) is intended to guide the conduct of the lawyer as an officer of the court as a prophylactic measure to protect against the contamination of the judicial process. Thus, for example, a lawyer who knows that a client has committed fraud on a tribunal and has refused to rectify it must disclose that fraud to avoid assisting the client's fraudulent act.
Misleading Legal Argument
 Legal argument based on a knowingly false representation of law constitutes dishonesty toward the tribunal. A lawyer is not required to make a disinterested exposition of the law, but must recognize the existence of pertinent legal authorities. Furthermore, as stated in paragraph (a)(3), an advocate has a duty to disclose directly adverse authority in the controlling jurisdiction which has not been disclosed by the opposing party. The underlying concept is that legal argument is a discussion seeking to determine the legal premises properly applicable to the case.
 When evidence that a lawyer knows to be false is provided by a person who is not the client, the lawyer must refuse to offer it regardless of the client's wishes.
 When false evidence is offered by the client, however, a conflict may arise between the lawyer's duty to keep the client's revelations confidential and the duty of candor to the court. Upon ascertaining that material evidence is false, the lawyer should seek to persuade the client that the evidence should not be offered or, if it has been offered, that its false character should immediately be disclosed. If the persuasion is ineffective, the lawyer must take reasonable remedial measures.
 Except in the defense of a criminal accused, an advocate must disclose, if necessary to rectify the situation, the existence of the client's deception to the court or to the other party. The lawyer's obligation to disclose also extends to material evidence given by others on behalf of the client. Such a disclosure can result in grave consequences to the client, including not only a sense of betrayal but also loss of the case and perhaps a prosecution for perjury. But the alternative is that the lawyer cooperate in deceiving the court, thereby subverting the truth-finding process which the adversary system is designed to implement. See Rule 1.2(d). Furthermore, unless it is clearly understood that the lawyer will act upon the duty to disclose the existence of false evidence, the client can simply reject the lawyer's advice to reveal the false evidence and insist that the lawyer keep silent. Thus the client could in effect coerce the lawyer into being a party to fraud on the court.
Perjury by a Criminal Defendant
 In the defense of a criminally accused, the lawyer's duty to disclose the client's intent to commit perjury or offer of perjured testimony is complicated by state and federal constitutional provisions relating to due process, right to counsel, and privileged communications between lawyer and client. While there has been intense debate over a lawyer's duty in such situations in criminal cases, this rule proposes to accommodate these special constitutional concerns in a criminal case by providing specific procedures and restrictions to be followed in the rare situations in which the client states his intention to, or does, offer testimony the lawyer knows to be perjured in a criminal trial.
 In such cases, it is the clear duty of the lawyer first to seek to persuade the client to refrain from testifying perjuriously. That persuasion should include, at a minimum, advising the client that such a course of action is unlawful, may have substantial adverse consequences, and should not be followed. If that persuasion fails, and the lawyer has not yet accepted the case, the lawyer must not agree to the representation. If the lawyer learns of this intention after the lawyer has accepted the representation of the client, but before trial, and is unable to dissuade the client of his or her intention to commit perjury, the lawyer must seek to withdraw from the representation. The lawyer must request the required permission to withdraw from the case by making an application ex parte before a judge other than the judge who will preside at the trial. The lawyer must request that the hearing on this motion to withdraw be heard in camera, and that the record of the proceedings, except for an order granting a motion to withdraw, be impounded.
 Once the trial has begun, the lawyer may seek to withdraw from the representation but no longer has an obligation to withdraw if the lawyer reasonably believes that to do so would prejudice the client. If the lawyer learns of the client's intention to commit perjury during the trial, and is unable to dissuade the client from testifying falsely, the lawyer may not stand in the way of the client's absolute right to take the stand and testify. If, during a trial, the lawyer knows that his or her client, while testifying, has made a perjured statement, and the lawyer reasonably believes that any immediate action taken by the lawyer will prejudice the client, the lawyer should wait until the first appropriate moment in the trial and then attempt to persuade the client confidentially to correct the perjury.
 In any of these circumstances, if the lawyer is unable to convince the client to correct the perjury, the lawyer must not assist the client in presenting the perjured testimony and must not argue the false testimony to a judge, or jury or appellate court as true or worthy of belief. Except as provided in this rule, the lawyer may not reveal to the court that the client intends to perjure or has perjured himself or herself in a criminal trial.
Duration of Obligation
 A practical time limit on the obligation to rectify the presentation of false evidence has to be established. The conclusion of the proceeding is a reasonably definite point for the termination of the obligation.
Refusing to Offer Proof Believed to Be False
 Generally speaking, a lawyer has authority to refuse to offer testimony or other proof that the lawyer believes is untrustworthy. Offering such proof may reflect adversely on the lawyer's ability to discriminate in the quality of evidence and thus impair the lawyer's effectiveness as an advocate. Whether constitutional requirements affect the resolution of this issue is beyond the scope of these comments.
Ex Parte Proceedings
 Ordinarily, an advocate has the limited responsibility of presenting one side of the matters that a tribunal should consider in reaching a decision; the conflicting position is expected to be presented by the opposing party. However, in any ex parte proceeding, such as an application for a temporary restraining order, there is no balance of presentation by opposing advocates. The object of an ex parte proceeding is nevertheless to yield a substantially just result. The judge has an affirmative responsibility to accord the absent party just consideration. The lawyer for the represented party has the correlative duty to make disclosures of material facts known to the lawyer and that the lawyer reasonably believes are necessary to an informed decision. Rule 3.3(d) does not change the rules applicable in situations covered by specific substantive law, such as presentation of evidence to grand juries, applications for search or other investigative warrants and the like.
 When adversaries present a joint petition to a tribunal, such as a joint petition to approve the settlement of a class action suit or the settlement of a suit involving a minor, the proceeding loses its adversarial character and in some respects takes on the form of an ex parte proceeding. The lawyers presenting such a joint petition thus have the same duties of candor to the tribunal as lawyers in ex parte proceedings and should be guided by Rule 3.3(d).
Corresponding ABA Model Rule. Identical in (a) to (d) to Model Rule 3.3 except in (a)(2) and (4); in (b) phrase "including all appeals" added; (e) new.
Corresponding Former Massachusetts Rule. DR 7-102, DR 7-106 (B), S.J.C. Rule 3:08, PF 12, DF 13.