Cordy, J.
Smaland Beach Association, Inc. (Smaland), together with the third-party defendants Allan Bartlett, Louise Johnson, Mark Johnson, Russell Johnson, William Smith, and Carol Mahoney, all of whom are directors, officers, or members of Smaland, appeal from a Superior Court judge’s order disqualifying their attorney, Lee Alfieri, from representing them in a real property dispute against Arthur and Patricia Genova (Genovas).3 The judge disqualified Alfieri based on his conclusion that Alfieri was a necessary witness because his clients had raised an advice of counsel defense and he had assisted various witnesses in submitting errata sheets that substantively changed their deposition testimony. We conclude that the judge failed to engage a sufficiently searching review of this fact-intensive issue. Consequently, we vacate the order and remand the case for a further hearing. We also take this occasion to consider the scope of disqualification orders under Mass. R. Prof. C. 3.7 (a), 426 Mass. 1396 (1998), and to clarify the proper use of errata sheets in altering deposition testimony under Mass. R. Civ. P. 30 (e), 365 Mass. 780 (1974).
1. Background. The details of the underlying substantive dispute are not material here, although we summarize them briefly for context. In 1971, the owners of various lots in a subdivision around Island Pond in Plymouth formally incorporated Smaland to maintain a beach and related recreational facilities for its members. Smaland commenced this action in 2005 against the Genovas, two of its members whose property shares a common boundary with a beach lot owned by Smaland.4 The complaint sought to ascertain the boundaries of the Genovas’ front property line and asserted claims of encroachment onto the Smaland lot, trespass and unlawful cutting of trees, tortious inter[216]*216ference with Smaland members’ use of a boat ramp and boat dock, and prescriptive easement over the Genovas’ property. The Genovas asserted counterclaims against Smaland to quiet title to the disputed areas, remove certain items from their property, and establish adverse possession of an area near and beneath their cottage. The Genovas also brought third-party claims against the officers and directors of Smaland alleging that the action brought against them constituted an abuse of process and that the conduct of the officers and directors violated fiduciary duties owed to the Genovas as Smaland members; and a third-party claim against a neighbor alleging that her retaining walls and stairs encroached onto the public road.
During the course of the lengthy litigation that ensued, the parties deposed a number of witnesses. Following their depositions, four third-party defendants and three other deponents submitted errata sheets that substantively changed their testimony. At various points in these errata sheets, the deponents wholly reversed their testimony from an affirmative to a negative response, or vice versa, struck existing testimony and replaced it with a different narrative, or added explanatory text to existing deposition testimony.5 Although some changes carried in-depth [217]*217explanations, the typical reason given was to “clarify testimony.” During the second day of their depositions, two of these deponents — both Smaland officers and third-party defendants — testified that their attorney, Alfieri, had assisted them in drafting the errata sheets.
In May, 2006, the parties filed their first joint pretrial memorandum, in which the Genovas listed Alfieri as a potential witness. At a hearing to discuss the bifurcation of the trial into nonjury and jury issues, a Superior Court judge (not the judge who entered the disqualification order) inquired into the need to call Alfieri. Alfieri represented that he did not believe he would be called as a witness at the trial and the Genovas’ counsel did not disagree. The judge subsequently issued an order bifurcating the trial6 and, in June, 2007, presided over the jury-waived trial, at which Alfieri was not called as a witness. The judge issued a decision in April, 2009.7
In advance of the jury trial on the remaining issues, the parties submitted a second joint pretrial memorandum, in which the Genovas again listed Alfieri as a potential witness. Smaland and the third-party defendants, like their adversaries, also filed [218]*218various pretrial motions, including a motion to prohibit the Genovas from calling Alfieri as a witness. The day before the hearing scheduled to consider these motions, the Genovas filed their opposition to this motion, expressing a conditional need to call Alfieri as a witness. The judge, however, treated the Genovas’ opposition as a motion to disqualify Alfieri, and focused the hearing on that issue.
At the start of the hearing, the judge instructed the parties that, on his reading of the bifurcation order, only three claims would proceed to trial8: (1) Smaland’s trespass claim, alleging that Arthur Genova entered its property and wrongfully cut down a tree; (2) the Genovas’ trespass and vandalism counterclaim, alleging that Smaland entered their property and removed granite survey markers and large rocks; and (3) the Genovas’ adverse possession counterclaim alleging that they had acquired title to a portion of their cottage, related retaining walls, garden, and bordering pathway that may technically lie on Smaland’s lot. Later in the hearing, he acknowledged that the Genovas’ breach of fiduciary duty claim against the third-party defendants was also appropriate for the jury trial.
After defining the scope of the impending jury trial, the judge identified two ways in which Alfieri had rendered himself a necessary witness and heard from both parties on the disqualification issue. First, the judge accepted that the third-party defendants had raised an advice of counsel defense to the Genovas’ breach of fiduciary duty claim.9 To the judge, if the third-party defendants invoked this defense at trial, the Genovas had a [219]*219“right” to call Alfieri. Second, the judge held that, given the highly unusual nature of the errata sheets that “totally change the deposition testimony,” both the Genovas and the appellants could use Alfieri’s testimony at trial. He went on to conclude that, while the Genovas would not be permitted to question Alfieri about what he had done for his clients, they would be allowed to inquire about the creation of the errata sheets submitted for nonclient witnesses, two of whom Alfieri admitted would be called as witnesses at trial. On learning from Alfieri that at least one of these nonclient witnesses suffered from memory loss, the judge further suggested that it would be reasonable for Smaland and the third-party defendants to call Alfieri to rehabilitate that witness and, perhaps, other witnesses who might be impeached through their errata sheet changes. The judge, therefore, issued an order from the bench disqualifying Alfieri from representing Smaland and the third-party defendants, though he recognized that they would suffer some hardship as a result.
Through Alfieri, the appellants moved for reconsideration. The judge ordered that the motion be “reserved pursuant to [Superior Court] Rule 9A upon [Smaland] as they are technically without counsel.” The appellants then petitioned a single justice of the Appeals Court for relief pursuant to G. L. c. 231, § 118, first par. Discerning “no abuse of discretion or clear error of law,” the single justice denied relief. Through new counsel, the appellants again moved the judge to take action on the motion for reconsideration. The judge determined “[n]o action necessary” because the Appeals Court had affirmed his prior mling. The appellants then brought this interlocutory appeal. We transferred the appeal here on our own motion.10
2. Discussion, a. Attorney disqualification.11 Rule 3.7 (a) of the Massachusetts Rules of Professional Conduct provides, in pertinent part, that a “lawyer shall not act as advocate at a trial [220]*220in which the lawyer is likely to be a necessary witness except where . . . disqualification of the lawyer would work substantial hardship on the client.”12 The primary purpose of the rule is “to prevent the jury as fact finder from becoming confused by the combination of the roles of attorney and witness.” Steinert v. Steinert, 73 Mass. App. Ct. 287, 291 (2008) (Steinert). See also comment [2] to rule 3.7 (“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”). It mitigates the potential negative perception by the public that the attorney colored his or her testimony to further the client’s case and relieves the opposing counsel of the difficult task of cross-examining his lawyer-adversary. Culebras Enters. Corp. v. Rivera-Rios, 846 F.2d 94, 99-100 (1st Cir. 1988). See Borman v. Borman, 378 Mass. 775, 786 (1979) (Borman); Serody v. Serody, 19 Mass. App. Ct. 411, 414 (1985) (Serody).
Despite these obvious benefits of the rule, it nonetheless carries with it the severe consequence of stripping a party of chosen counsel. Because of this, judges must proceed with “deliberate caution” when considering the disqualification of an attorney. Rizzo v. Sears, Roebuck & Co., 127 F.R.D. 423, 424 (D. Mass. 1989), citing Borman, supra, and Serody, supra. They must reconcile “the right of a person to counsel of his choice on the one hand, and the obligation of ‘maintaining the highest standards of professional conduct and the scrupulous administration of justice,’ on the other.” Slade v. Ormsby, 69 Mass. App. Ct. 542, 545 (2007) (Slade), quoting Mailer v. Mailer, 390 Mass. 371, 373 (1983).
As this analysis hinges in large measure on a judge’s balancing of the respective prejudices to the parties, we review disqualification orders for an abuse of discretion. Kendall v. Atkins, 374 Mass. 320, 324 (1978) (Kendall). See Steinert, supra at 288. Yet, we must be mindful that “[disqualification is [221]*221not required in every case in which counsel could give testimony on behalf of his client on other than formal or uncontested matters,” Byrnes v. Jamitkowski, 29 Mass. App. Ct. 107, 109 (1990), citing Borman, supra, nor is it automatically granted where a party attempts to call opposing counsel, Borman, supra at 792. Rather, our framework requires a more searching review to determine whether the lawyer’s “continued participation as counsel taints the legal system or the trial of the case before it.” Id. at 788.
To that end, judges must carefully examine the evidence before them and should consider whether the information sought from the attorney-witness can be presented in a different manner, whether the attorney-witness’s testimony would be cumulative or marginally relevant, or whether disqualification was a foreseeable outcome. See Kendall, supra at 325; Serody, supra at 414; comment [4] to rule 3.7 (“It is relevant that one or both parties could reasonably foresee that the lawyer would probably be a witness”). Where the need for an attorney to testify on behalf of his client arises, judges should defer to “the best judgment of counsel and his client,” unless the attorney is “withhold[ing] crucial testimony from his client because he prefers to continue as counsel.” Borman, supra at 790. But where opposing counsel seeks to question the attorney, “[t]he matter lies differently . . . .” Serody, supra at 413. In such cases, judges must guard against the “the Canons of Ethics [being] brandished for tactical advantage,” and must prevent litigants from wielding the rule as a weapon to “maneuver [opposing counsel’s] withdrawal and to that degree unsettle the adversary.”13 Id. at 414. Although such scrutiny typically discourages the practice of allowing a party to call opposing counsel as a witness, where the testimony sought is prejudicial to or directed against the client, “the case for judicial intervention is more powerful.” Id. at 413. See Kendall, supra at 324.
Because the judge grounded his decision in two independent [222]*222courses of conduct, we explore each path to disqualification in turn. First, we recognize that an attorney may be deemed a necessary witness when his clients assert an advice of counsel defense. See, e.g., Sea Trade Maritime Corp. vs. Coutsodontis, No. 09 Civ. 488 (BSJ) (HBP) (S.D.N.Y. July 25, 2011) (permitting attorney disqualification where advice of counsel defense raised). The content of that defense requires, among other things, a showing that the clients made a full and honest disclosure of material facts to the attorney and that they followed the attorney’s advice. G.S. Enters., Inc. v. Falmouth Marine, Inc., 410 Mass. 262, 275 (1991). Surely, it might be reasonable to call the attorney who rendered the advice. But just because inclusion of such testimony would be reasonable in some instances does not mean it is required in all.
When faced with disqualification stemming from this defense, a judge must still undertake the analysis discussed above, and consider whether the information sought from an attorney could be adduced through other means. See Kendall, supra at 324-325; Serody, supra at 414. Here, there is no indication that the judge conducted that inquiry, and the record before us does not enable us to do so. The Genovas have not articulated the expected content of Alfieri’s testimony, nor have they explained what it may offer beyond the testimony of the parties themselves.14 The record is equally devoid of any reason why Alfieri must testify to defend his clients. Such strategic decisions rest with the attorney and his client, unless a judge concludes that the attorney’s failure to testify is “obviously contrary to the client’s interests.” Borman, supra at 791. Absent these additional findings, Alfieri’s disqualification on the ground that his clients have asserted an advice of counsel defense rests on speculation, which is “plainly insufficient to serve as a basis for disqualification."15 Steinert, supra at 290.
[223]*223The second path to Alfieri’s disqualification originates in his role in drafting the errata sheets that substantively change the deposition testimony of his client and nonclient witnesses. Throughout the hearing, the judge emphasized the unusual nature of these documents. We do not disagree. Our review of the errata sheets reveals that meaningful changes were made to the underlying testimony, and their consistent use across witnesses calls into question Alfieri’s role in their creation. Yet, given the prospective uses of Alfieri’s testimony, these facts alone do not provide adequate justification for concluding that the attorney is a necessary witness.
First, in accepting the Genovas’ argument that Alfieri was needed to explain the creation of the errata sheets, the judge failed to explore whether the testimony sought would be prejudicial to or directed against Alfieri’s clients, or whether alternate sources for this information were available. Such analysis is crucial in justifying judicial intervention into the attorney-client relationship where a party seeks the testimony of opposing counsel. See Kendall, supra at 325; Serody, supra at 414.
Here, however, the judge did not engage this inquiry, and the record that was before him does not allow us to do so.16 In the first instance, there is again no evidence of the likely content of Alfieri’s testimony, which inhibits our investigation of the potential [224]*224harm it could cause his clients without steering us toward impermissible speculation. In the second, the judge’s dialogue at the hearing disregarded the likelihood that most witnesses would be capable of recalling how their errata sheets were created and the possibility that any explanation of the process may have been preserved in deposition testimony. For example, on the second day of her deposition, the witness identified as suffering from memory loss explained that she marked changes on a deposition transcript that Alfieri had provided to her and delivered those changes to him. According to the witness, Alfieri then “wrote it up in better language than what... I had. But I made the corrections first and brought them down to . . . Alfieri.” Perhaps this passage would serve as an adequate explanation of the errata sheets for the parties to present to the jury. We do not know. The bulk of the underlying deposition transcripts was not before the judge at the disqualification hearing.
Similar flaws are apparent in the judge’s conclusion that Alfieri may have to testify to rehabilitate any witnesses impeached through their errata sheets changes, and, thus, “properly defend his client.” Through the use of the errata sheets at trial, the jury would be in a position to consider the memories of the witnesses and their ability to remember a given fact at a certain time. On the record before us, it appears that Alfieri is in no better position to speak to these issues than the witnesses themselves, nor is he better poised than the jury to judge the apparent discrepancies. In any event, the decision to call Alfieri to rehabilitate a witness, and thus testify on behalf of his clients, initially lies with him, as the attorney, and his clients. Borman, supra at 787-788. They could reasonably decide that the witnesses could overcome any impeachment without Alfieri’s testimony. Without additional findings, any decision to forgo Alfieri’s testimony does not appear to contradict the clients’ interests so dramatically as to warrant judicial intervention. See id. at 790-791.
The decision to disqualify an attorney is a difficult one with substantial consequences to the attorney’s client, particularly, as here, where the case has been litigated by the attorney over many years. As such, judges considering these motions must closely scrutinize the facts before them to determine whether a [225]*225lawyer’s “continued participation as counsel taints the legal system.” Id. at 788. Given the accusations of attorney misconduct in the preparation of the errata sheets, it may be that, after further review, the judge will again disqualify Alfieri. Even with that possibility, the present order cannot stand on the record before us. Although the decision came on the eve of trial, the judge did not sufficiently analyze the factors before him, particularly in light of the narrow issues for the jury trial he proscribed. Therefore, we vacate the disqualification order and remand the case for a further hearing consistent with this opinion.17
b. Pretrial disqualification. Although we have vacated the judge’s order, the total disqualification he imposed on Alfieri compels us to offer some guidance on the subsequent review of this issue.
By its plain language, rule 3.7 (a) prohibits a lawyer from acting “as an advocate at trial in which the lawyer is likely to be a necessary witness” (emphasis added). Unlike the rules governing disqualification due to conflicts of interest with the lawyer-witness’s current client or prior representation of the opposing party, this rule contains the limiting phrase “at trial.” Contrast Mass. R. Prof. C. 1.7, 426 Mass. 1330 (1998) (conflict of interest); Mass. R. Prof. C. 1.9, 426 Mass. 1342 (1998) (prior representation). It also focuses on a lawyer’s specific role as an advocate at that trial, thus differentiating this rule from its predecessor, which broadly prohibited a lawyer who ought to serve as a witness from participating in “the conduct of the trial” (emphasis added). Disciplinary Rule 5-102 (A), 359 Mass. 814 (1972). While the former rule could — and had been — read to encompass a lawyer-witness’s pretrial representation of his client, we are persuaded that the current rule does not. See Culebras Enters. Corp. v. Rivera-Rios, 846 F.2d 94, 99 (1st Cir. 1998) (Culebras) (Rule 3.7 of Model Rules of Professional Conduct of American Bar Association [ABA], which is identical to Massachusetts rule, should not be read “as broadly prohibiting the rendition of case-related out-of-court services prior to trial”); Steinert, supra at 290-291 (rule 3.7 “does not limit [226]*226the attorney’s involvement prior to trial”). Compare Massachusetts Bar Association Committee on Professional Ethics Opinion No. 88-6 (1988) (concluding that Disciplinary Rule 5-102 [A] prohibited lawyer-witness from participating in pretrial activities, while recognizing that model rule 3.7, which is identical to current Massachusetts rule, was “a much less restrictive disqualification provision”) with ABA Standing Committee on Ethics and Professional Responsibility Informal Opinion 89-1529 (1989) (concluding that model rule 3.7 permits lawyer-witness representation in pretrial activities provided client consents after consultation). As such, an attorney considered to be a necessary witness may participate in pretrial proceedings, though it would be particularly prudent first to secure client consent after consultation.18 See id.
This reading of rule 3.7 (a) adheres to its text and fulfils its underlying purposes. See Culebras, supra at 99-100. That is, because the rule strives to mitigate potential jury confusion, to avoid the difficulties of cross-examining an adversary and to diminish the appearance of impropriety where an attorney “leave[s] counsel table for the witness chair,” Serody, supra at 414, judges need only divorce the two functions —• that of advocate and witness — at the trial itself. Id. at 414-415. These concerns, however, “are absent or, at least, greatly reduced, when the lawyer-witness does not act as trial counsel, even if he performs behind-the-scenes work for the client in the same case.” Culebras, supra at 100.
Thus, were the judge to ground any future disqualification of Alfieri in rule 3.7 (a) alone, he is limited to barring the attorney’s participation at trial.19 Any disqualification that might [227]*227extend to pretrial activities must derive from a different source.20
c. Judicial disqualification,21 Smaland and the third-party defendants ask that we disqualify the motion judge from further involvement in the case on remand. We find nothing in the record to suggest that the judge’s “impartiality might reasonably be questioned,” and therefore decline to disqualify him. S.J.C. Rule 3:09, Canon 3 (E) (1), as appearing in 440 Mass. 1319 (2003). Despite the appellants’ arguments to the contrary, the judge acted within his authority when he raised the issue of Alfieri’s disqualification after the opposing party signaled its conditional intention to call Alfieri as a witness. See Kendall, supra at 325. That the resulting order was adverse to the appellants does not demonstrate the required “bias or prejudice” to warrant judicial disqualification. Commonwealth v. Greineder, 458 Mass. 207, 235 (2010), quoting Commonwealth v. Adkinson, 442 Mass. 410, 415 (2004).
d. Errata sheets. Errata sheets have played a central role in the litigation among the parties, and Smaland and the third-party defendants have argued that any substantive changes contained within the errata sheets were proper under Mass. R. Civ. P. 30 (e). Although the validity of the errata sheets is not directly before us, we nonetheless take this opportunity to clarify the use of errata sheets to alter deposition testimony.
Rule 30 (e) allows that “[a]ny changes in form or substance which the witness desires to make shall be entered upon the deposition by the officer with a statement of reasons given by [228]*228the witness for making them.” No Massachusetts appellate court has squarely decided the propriety under this rule of submitting substantive changes to deposition testimony through errata sheets.22 Because the Massachusetts and Federal rules are similar, it is instructive to turn to our Federal counterparts for guidance.23 See Strom v. American Honda Motor Co., 423 Mass. 330, 335 (1996), quoting Solimene v. B. Grauel & Co., 399 Mass. 790, 800 (1987), and Rollins Envtl. Servs., Inc. v. Superior Court, 368 Mass. 174, 180 (1975) (“ ‘Because the Massachusetts Rules of Civil Procedure are patterned after the Federal rules, we interpret our rules consistently with the construction given their Federal counterparts,’ . . . ‘absent compelling reasons to the contrary or significant differences in content’ ”).
As courts and commentators have noted, divergent trends have emerged across the national landscape as Federal courts have grappled with this issue. See, e.g., Reilly v. TXU Corp., 230 F.R.D. 486, 487 (N.D. Tex. 2005) (Reilly); Summerhouse v. HCA Health Servs. of Kan., 216 F.R.D. 502, 504-505 (D. Kan. 2003); Macchiaroli, Rewriting the Record: A Federal Court Split on the Scope of Permissible Changes to a Deposition Transcript, 3 Fed. Cts. L. Rev. 1, 4-10 (2009). The traditional approach, adopted in the majority of Federal courts, allows any changes, whether in form or substance, clarifying or contradictory. Reilly, supra at 489-490. See, e.g., Podell v. Citicorp Diners Club, Inc., 112 F.3d 98, 103 (2d Cir. 1997); Tingley Sys., Inc. v. CSC Consulting, Inc., 152 F. Supp. 2d 95, 120 (D. Mass. 2001) (Tingley); Lugtig v. Thomas, 89 F.R.D. 639 (N.D. Ill. 1981) [229]*229(Lugtig). To mitigate the potential for abuse under this liberal view, courts implementing this approach have allowed the original and changed answers, as well as any reasons given for the changes, to remain part of the record, Lugtig, supra at 641-642, and “reserved the right to reopen the deposition if the changes were material,” Summerhouse v. HCA Health Servs. of Kan., supra at 505, citing Tingley, supra at 120-121.
A growing minority of courts has, however, adopted a narrower interpretation of Fed. R. Civ. P. 30 (e), either restricting the rule to typographical or transcription corrections, see, e.g., Greenway v. International Paper Co., 144 F.R.D. 322, 325 (W.D. La. 1992), or permitting clarifying, but not contradictory changes, see, e.g., Hambleton Bros. Lumber Co. v. Balkin Enters. Inc., 397 F.3d 1217, 1225-1226 (9th Cir. 2005).24
Given the plain language of our rule 30 (e), which encompasses “[a]ny changes in form or substance” to deposition testimony, we adopt the majority approach. Unlike the minority view, which imposes an artificial stricture on the analogous Federal rule, this scheme allows legitimate corrective changes and advances the underlying purpose of the discovery process, i.e., “for the parties to obtain the fullest possible knowledge of the issues and facts before trial.” Strom v. American Honda Motor Co., supra at 336, quoting Hickman v. Taylor, 329 U.S. 495, 501 (1947). See Reilly, supra at 490.
Yet, we do not import this expansive reading without limitations necessary to guard against manipulation of rule 30 (e). First, counsel must understand and should explain to deponents that any changes they make must represent their own good faith [230]*230belief, and may not be undertaken simply to bolster the merits of a case. Second, counsel must ensure that any submitted changes comply with the procedural requirements of rule 30 (e). See Lugtig, supra at 641-642. We emphasize, in particular, the instruction that a statement of reasons must accompany the change. Mass. R. Civ. P. 30 (e). These reasons must be advanced in good faith and provide an adequate basis from which to assess their legitimacy; that is, they must not be conclusory. Tingley, supra at 119-120.
Like other courts employing a similar interpretation of rule 30 (e), we also adopt certain remedial measures. See Lugtig, supra at 642. First, because the text of rule 30 (e) does not require that the original answers of the deponent be struck, the original answers remain part of the record and may be read, along with the changed answers and reasons provided for the change, at trial. See id. at 641. Second, in the interest of fairness, where the deponent has made substantive changes as to significant matters on an errata sheet that, if provided during the deposition, would reasonably have triggered further inquiry, the party who took the deposition can reopen the examination for the purposes of exploring matters raised by the substantive changes in testimony and the origins of those changes.25 Finally, if there is any indication that an attorney has exploited the rule by arranging or facilitating the submission of errata sheets for the purpose of strategic gain in a case and not to correct testimony, his conduct may be grounds for sanctions. See, e.g., Mass. R. Prof. C. 3.3, 426 Mass. 1383 (1998) (candor toward tribunal); Mass. R. Prof. C. 3.4 (a)-(d), (f), (g), 426 Mass. 1389 (1998) (fairness to opposing party and counsel).
While substantive changes to errata sheets are permitted under rule 30 (e), we caution deponents and attorneys to invoke this privilege sparingly. The errata sheet is intended as a tool to correct mistakes in deposition testimony or subsequent transcription. It is not to be used as a mechanism to inject additional facts into the testimony of a single deponent, or to align testimony across deponents.
[231]*2313. Conclusion. The judge’s disqualification order is vacated and the case is remanded for further proceedings consistent with this opinion.
So ordered.