This case presents the question whether two former attorneys for the District of Columbia violated DR 9-101(B) by accepting private employment in a “matter” for which they had substantial responsibility while in government. We hold that the present transaction — an application to the Board of Zoning Adjustment (BZA) for a special exception to permit additional off-street parking — is not the same as, or substantially related to, any matter these at*40torneys handled for the District. We affirm the unanimous BZA ruling that these individual attorneys, as well as intervenors’ law firm, Wilkes & Artis, are not disqualified from this case.1
I.
In Brown v. District of Columbia Board of Zoning Adjustment, 413 A.2d 1276 (D.C.1980) (Brown I), we noted that two lawyers with intervenor Carr’s law firm, Iverson Mitchell and C. Francis Murphy, had served as counsel for the District of Columbia in two earlier transactions allegedly related to this one. Thus, we remanded the record to the BZA “for a determination of whether intervenor Carr’s counsel should be disqualified because of previous responsibility for the same matter while employed by the District of Columbia.” Id. at 1282. Specifically, we instructed the BZA to determine whether the present transaction and the two earlier ones concerning Oliver T. Carr’s property in the Commercial-Residential (CR) Zone in the West End section of the District were the same “matter,” within the meaning of DR 9-101(B). Id. at 1283,1284. The three transactions are:
1.Litigation commenced by Carr in April 1975 against the Zoning Commission challenging, on Fifth Amendment grounds, the 60-foot height limitation on the property, in contrast with the general 90-foot height limitation in the rest of the zone. Carr’s litigation, defended for the District by Mitchell, was successful; it increased the usable floor-area ratio for Carr’s property from approximately 4.5 to 6.0 and thus increased the allowable rentable space.
2. Conversations and correspondence in October 1975 between Carr’s attorneys and Corporation Counsel lawyers, including Murphy and Mitchell, about the legality of Carr’s proposed air rights condominium that would mix residential and commercial uses on the same property. Carr abandoned the proposal for reasons unrelated to legal issues.
3. The present case: a 1977 application for a special exception under the zoning regulations to increase the number of below-grade parking spaces permitted for the residential “Westbridge” development on Carr’s property. The firm of Wilkes & Artis — which Murphy and Mitchell had joined in 1976 — represents Carr (another firm had represented Carr in the first two transactions). Mitchell’s name was on some of the pleadings; neither Mitchell nor Murphy was effectively screened from participation.2
*41After remand, the BZA held a hearing, reviewed the testimony, and determined that the three transactions were not the same “matter.” The BZA accordingly concluded the disqualification of Wilkes & Ar-tis (based on the presence of Murphy and Mitchell) was not required.3
A division of this court, with one judge dissenting, reversed the BZA ruling after concluding, as a matter of law, that the special exception case at issue here constitutes the same “matter” as the two earlier transactions, within the meaning of DR 9-101(B). Brown v. District of Columbia Board of Zoning Adjustment, No. 13670 (D.C. July 15, 1983) (Brown II). Again, the division remanded the record to the BZA. Id., slip op. at 27. Before further proceedings, however, this court granted respondent’s petition for rehearing en banc and vacated the division opinion in Brown II (order filed Sept. 29, 1983).
II.
In Committee for Washington’s Riverfront Parks v. Thompson, 451 A.2d 1177 *42(D.C.1982), we implicitly concluded that, under DR 9-101(B), matters will be deemed the same if substantially related to one another.4 It is useful, preliminarily, to review why that test evolved and how it generally applies.
A.
The “substantially related” test originated in litigation between private parties. T. C. Theatre Corp. v. Warner Brothers Pictures, Inc., 113 F.Supp. 265 (S.D.N.Y.1953), aff'd, 216 F.2d 920 (2d Cir.1954). The court considered a motion to disqualify counsel on the ground of unethically “switching sides” — of improperly taking legal action against a former client. The court was concerned, primarily, about a violation of Canon 6 of the ABA Canons of Professional Ethics (restated as Canon 4 of the ABA Code of Professional Responsibility), enjoining lawyers to preserve client confidences and avoid conflicts of interest. The question, therefore, was whether counsel may have received confidential information from the former client that could be used against it in the subsequent representation. 113 F.Supp. at 268-69. The court announced the following rule; “Where any substantial relationship can be shown between the subject matter of a former representation and that of a subsequent adverse representation, the latter will be prohibited.” Id. at 268 (footnote omitted).5
*43Courts considering side-switching from one private client to another have consistently followed this formulation. E.g., Trone v. Smith, 621 F.2d 994, 998 (9th Cir.1980); Government of India v. Cook Industries, Inc., 569 F.2d 737, 739-40 (2d Cir.1978). The question for us, of course, is how this side-switching case law applies in the “revolving door” context — in our case a government attorney who leaves to join a private firm and begins to represent clients against, or before an agency of, the former government employer. See generally “Revolving Door, ” 445 A.2d 615 (D.C. 1982) (en banc).6
B.
The first significant case to consider a revolving door disqualification was United States v. Standard Oil Company, 136 F.Supp. 345 (S.D.N.Y.1955) (Kaufman, J.). The court not only invoked old Canons 6 and 37 (avoiding conflicts of interest and preserving client confidences) but also applied the revolving door rule of old Canon 36: “A lawyer, having once held public office or having been in the public employ, should not after his retirement accept employment in connection with any matter which he has investigated or passed upon while in such office or employ.” The court stressed that the purpose of Canon 36 “was to clarify the duties in Canon 6 as related to government attorneys,” id. at 361, with a view to preventing “even the appearance that the government servant may take a certain stand in the hope of later being privately employed to uphold or upset what he had done.” Id. at 359 (footnote omitted).
While recognizing this preventive purpose, the Standard Oil court imported into Canon 36 the same “substantially related” test used to evaluate private side-switching and thus the same focus on preventing misuse of confidential information. Id. at 353-55 (citing T. C. Theatre Corp.). The court expressly recognized “it is doubtful if the Canons of Ethics are intended to disqualify an attorney who did not actually come into contact with materials substantially related to the controversy at hand when he was acting as attorney for a former client now adverse to his position.” Id. at 364. The court added, however, that a “complainant need only show access to such substantially related material and the inference that defendant received these confidences will follow.” Id. at 354 (emphasis in original) (footnote omitted); see supra note 5.7 Moreover, “where there is *44a close question as to whether particular confidences of the former client will be pertinent to the instant case, an attorney should be disqualified to avoid the appearance if not the actuality of evil.” Id. at 364.
Revolving door cases under Canon 9 of the ABA Code of Professional Responsibility (Avoiding Even the Appearance of Impropriety) have continued to reflect the Standard Oil court’s emphasis on preserving client confidentiality. Kg., Board of Education v. Nyquist, 590 F.2d 1241, 1246 (2d Cir.1979); see Committee for Washington’s Riverfront Parks, 451 A.2d at 1188, 1191, 1192.8
C.
Revolving door cases, however, also address concerns in addition to confidentiality. As the Standard Oil court itself recognized, 136 F.Supp. at 359, the public must be protected against the possibility that government attorneys in a variety of ways will conduct “their offices with an eye toward future private employment,” whether by law firms or prospective clients. United States v. Ostrer, 597 F.2d 337, 340 (2d Cir.1979); accord Woods v. Covington County Bank, 537 F.2d 804, 814 (5th Cir.1976); General Motors Corporation v. City of New York, 501 F.2d 639, 650 n. 20 (2d Cir.1974); see ABA Comm, on Professional Ethics, Opinion No. 37 (1931) (former ABA Canon 36 intended to deter government lawyers from being influenced “by the hope of later being employed privately either to uphold or to upset what [they] had done”).9 In Standard Oil, however, the court did not address these other concerns in order to determine whether the “substantially related” test was sufficiently responsive. We do so here.
We therefore turn to a second concern from the revolving door, arising from the fact that government attorneys often have *45access to information that is generally not available to the private sector, even through discovery. They have access, for example, to grand jury proceedings and classified documents. Woods, 537 F.2d at 816. They also are often in a position to obtain statements from witnesses who, but for their willingness to respond to a government official, might be disinclined to cooperate. Id. Courts and the bar have called it fundamentally unfair for a former government attorney, newly in private practice, to use “specific information obtained by the exercise of government power” — information that otherwise would not be available to his or her client — to the prejudice of opposing private party litigants. Id. at 817; Allied Realty of St. Paul, Inc. v. Exchange National Bank of Chicago, 283 F.Supp. 464, 468 (D.Minn. 1968), aff'd, 408 F.2d 1099 (8th Cir.), cert. denied, 396 U.S. 823, 90 S.Ct. 64, 24 L.Ed.2d 73 (1969); ABA Comm, on Professional Ethics & Grievances, Formal Op. No. 135. This unfairness exists even if the former client, the government, is not prejudiced by the lawyer’s subsequent use of the information. Accordingly, Canon 9 may require disqualification even though in a literal sense no side-switching takes place, i.e., even though the former government attorney later takes a position for a private client wholly consistent with the position he or she took on behalf of the government.
There is a third concern: the lure of private practice may undermine a government attorney’s responsibilities to the public. In the first place, some government attorneys enjoy more latitude than private attorneys in deciding how to spend their time and their client’s resources. Whereas a private attorney is limited to accepting or rejecting matters that prospective clients present, government attorneys in various agencies, at least above certain levels of the bureaucracy, have the power to define and shape their client’s priorities. Thus, if a government attorney could anticipate changing employers to exploit his or her knowledge of a particular ease for private gain — even without taking sides against the government — there is a real possibility that government counsel could channel government resources into cases primarily suited to eventual, lucrative employment, rather than into cases more clearly in the public interest. Compare General Motors Corp., 501 F.2d at 650 (former Department of Justice lawyer, who had represented government in antitrust action against General Motors, disqualified from later bringing similar suit against General Motors on behalf of private party) and Allied Realty of St. Paul, 283 F.Supp. at 469 (former Assistant United States Attorney disqualified from representing private party in civil mortgage fraud action against bank, having represented government in criminal fraud action against bank on same claim) with Woods, 537 F.2d at 814 (former reserve officer in Navy Judge Advocate General’s Corps, who laid groundwork for suit on behalf of former prisoners of war on instructions of superiors, did not have authority or opportunity to direct resources and thus was not barred from representing POWs in private suit).
Similarly, while not initiating a case for later private purposes, a government attorney could structure a case in a way that might leave room for later private employment; e.g., the attorney could fashion a government complaint by adding or omitting a count that could help serve a later private action against the same defendant. Finally, in dealing with regulations or agency policies, a government attorney could neglect his or her duties in a way that later could inure to the benefit of a private employer in a case related to that neglect; e.g., an attorney could pass upon, or shirk a clear duty to pass upon, the validity of a regulation in a way calculated eventually to exploit special knowledge of the weaknesses of that regulation in private practice. See Standard Oil, 136 F.Supp. at 359.
These first three concerns, reflecting the potential misuse of government-developed information, are addressable by an ethical rule, such as DR 9-101(B), barring former *46government attorneys from participating in, and benefiting from, later transactions related to particular matters they handled for the government.10 But there are several other concerns from the revolving door that exist even when the attorney’s later work on behalf of private clients would have no identifiable relationship to particular government matters that the attorney previously had handled.
Thus, a fourth concern is that an attorney may at times choose to be over-zealous or under-zealous in representing the interests of the government client in the hope of “currying favor” with private sector employers and later being rewarded with private employment on unrelated matters.
Fifth, while in government, an attorney may develop a reputation by initiating or promoting policies that are calculated to advance that attorney’s marketability in the private sector without regard to any particular kind of case.
Sixth, after leaving the government, an attorney may make use of expertise — special knowledge of agency policies, practices, and procedures acquired while on the government payroll — to the advantage of private clients.
Seventh, after leaving the government, an attorney may make use of government contacts (old friends) to gain special advantage for private clients.
No prophylactic rule short of a total ban on the revolving door itself could address these last four concerns since the post-government representation could not be barred simply by reference to previous participation in a related government matter. What is striking here, therefore, is the fact that, although we have identified seven concerns attributable to the revolving door, only the first three are addressed by the DR 9-101(B) disqualification for participation in substantially related matters.11 The others, to the extent regulated at all, are covered — and only recently so — by criminal sanctions under the Ethics in Government Act of 1978, 18 U.S.C. § 207(c) (1982), barring specified federal and District government employees from appearing as agents or attorneys before their former government departments or agencies for a period of one year, without regard to what they may have handled while in government.12
One could argue, of course, that the prophylactic effect of DR 9-101(B) should be extended — in the spirit of § 207(c) — to cover appearances that do not necessarily reflect established or likely corruption of the subsequent litigation. The only basis for doing so, however, would be a policy judgment that, despite the absence of any prej*47udicial relationship between a government transaction and a former government attorney’s later work for a private client, the attorney’s government reputation, expertise, and contacts should, for the sake of appearances, be kept from the new private client. As the Legal Ethics Committee of the Bar has recognized, however, see supra note 11, neither the language of DR 9-101(B) nor its history indicates a purpose to define substantially related matters broadly enough to require disqualification solely on the basis of unseemly appearances.13
No one can dispute that government service affords lawyers the opportunity to impress potential employers, through legitimate or illegitimate means. The nature of the job brings government attorneys into contact with private practitioners and clients interested in their fields of expertise. If this reality alone could provide the basis for perpetual disqualification under DR 9-101(B) — as, in effect, it does during the one-year ban under § 207(c) of the Ethics in Government Act of 1978, supra, —then we would, for example, deter Federal Communications Commission lawyers from leaving government to practice, or join firms specializing in, communications law. We would deter Public Service Commission lawyers from leaving government to practice in the utilities field — and so on. Because the practice of law is becoming
increasingly specialized, particularly in this jurisdiction where many administrative agencies are headquartered, we believe the likely consequence of such a wholesale approach to disqualification would be encouragement of a two-track — government lawyer, private lawyer — professional structure. We would eliminate the suspicion and the reality of ethical improprieties unrelated to particular government cases, but only at the cost of creating an insular, permanent legal bureaucracy. See generally Developments in the Law: Conflicts of Interest, 94 Harv.L.Rev. 1244, 1428-30 (1981). We believe such a pervasive ban— far more severe than the one-year limit under § 207(c) — would deter too many capable attorneys from entering government service, to the detriment of the public. See supra note 12.
In sum, despite the many legitimate concerns about the revolving door, only three improprieties are addressed by DR 9-101(B). The lawyer: (1) may disclose confidential information to the prejudice of the government client; (2) may use information obtained through the exercise of government power to the prejudice of opposing private litigants; and (3) while in government, may have initiated, structured, or neglected a matter in the hope of *48using it later for private gain. See supra note 10.
D.
The question, then, is whether revolving door rule DR 9-101(B), reflecting two concerns in addition to protection of client confidentiality, should be interpreted to prescribe stricter criteria for attorney disqualification than the “substantially related” test that applies when an attorney switches sides from one private client to another.
Subject to a few refinements, we see no basis for a different test. In addition to forestalling breaches of confidentiality, the “substantially related” test — designed to prevent abuse of government-developed information — obviously covers the second potential impropriety. An opposing litigant cannot claim prejudice from the use of information acquired by the exercise of government power unless it can “reasonably be said that during the former representation the attorney might have acquired information related to the subject matter of the subsequent representation.” Cannon v. U.S. Acoustics Corp., 398 F.Supp. 209, 223 (N.D.Ill.1975), aff'd in relevant part, 532 F.2d 1118 (7th Cir.1976).
In cases implicating the third potential impropriety — initiating, structuring, or neglecting government representation with a view to private gain from the same or a related matter — the concern is not so much the attorney’s eventual conduct in private practice; it is, rather, that the private conduct casts doubt on the integrity of the attorney’s earlier public service. Woods, 537 F.2d at 814. Once again, however, unless a court could find that the attorney might have acquired information relevant to the eventual private action during the course of government employment, it is unlikely that the attorney developed the government case or neglected assigned responsibilities with the later, private action in mind.14 Thus, the “substantially related” test is responsive as well to this third category of potential abuse.15
We conclude that the DR 9-101(B) revolving door rule, like a side-switching rule, is designed to address “at least a reasonable possibility that some specifically identifiable impropriety” would occur. Woods, 537 F.2d at 813. “It cannot be a fanciful, unrealistic or purely subjective suspicion of impropriety that requires disqualification.” United States v. Smith, 653 F.2d 126, 128 (4th Cir.1981). As we see it, therefore — and here is the key to this case — only if specific information (as distinct from general agency expertise or contacts) that a former government lawyer may have had access to in one matter is likely to be useful in a subsequent matter, will there be a reasonable possibility of the *49particular improprieties that DR 9-101(B) is intended to forestall.16
E.
There remains the question of the methodology for determining whether two matters are substantially related, such that a former government attorney may have had access to information useful in the subsequent proceeding. In determining whether private matters are “substantially related,” the courts have examined both the facts and the legal issues involved. “Initially, the trial judge must make a factual reconstruction of the scope of the prior legal representation.” Westinghouse Electric Corp. v. Gulf Oil Corp., 588 F.2d 221, 225 (7th Cir.1978). If the factual contexts overlap, the court then has to determine “whether it is reasonable to infer that the confidential information allegedly given would have been given to a lawyer representing a client in those [prior] matters.” Id. Finally, if such information apparently was available to counsel in the prior representation, the court has to determine whether it “is relevant to the issues raised in the litigation pending against the former client.” Id. If all three conditions are met, the matters will be substantially related and thus deemed the same for conflict-of-interest purposes, with doubts to “be resolved in favor of disqualification.” Id.; see Standard Oil Co., 136 F.Supp. at 354, 364.
While the “substantially related” test is basically the same for private side-switching and DR 9-101(B) revolving door cases, there are three reasons (related to the possible misuse of government-developed information) why the court must be especially careful in applying the test to former government attorneys — reasons that suggest a few refinements of the test under DR 9-101(B). First, because government attorneys may have had access to more kinds of information in connection with the prior representation than private attorneys typically do, there is a greater potential for misuse of information — including information that is not necessarily confidential in nature, see supra note 15 — in the revolving door context. Second, the public is generally more concerned about government improprieties than about private improprieties. Thus, the appearance problem is more severe because the public is likely to be more critical of this potential misuse of information. Third, unlike a case of private side-switching, the party who seeks disqualification under DR 9-101(B) may not have been involved in the prior legal transaction. Consequently, the complainant may not have specific enough knowledge of the information gathered in the earlier transaction to proffer adequate support for the motion to disqualify, unless there is sufficient access to it through discovery.
Accordingly, in cases where the complainant’s evidence shows that the factual contexts of the two (or more) transactions overlap in such a way that a reasonable person could infer that the former *50government attorney may have had access to information legally relevant to, or otherwise useful in, the subsequent representation, we conclude that the complainant will have established a prima facie showing that the transactions are substantially related.17 The burden of producing evidence that no ethical impropriety has occurred will then shift to the former government attorney, who must rebut complainant’s showing by demonstrating that he or she could not have gained access to information during the first representation that might be useful in the later representation.18 Absent sufficient rebuttal, the complainant will have carried the burden of persuasion as the moving party.
It is important to stress that the attorney cannot meet this rebuttal burden simply by claiming that no useful information was, in fact, received in the first matter. If the factfinder is persuaded that two matters are substantially related — i.e., that it is reasonable to infer counsel may have received information during the first representation that might be useful to the second — there arises a conclusive inference that useful information was, in fact, received. See Westinghouse Electric Corp., 588 F.2d at 224 & n. 3; Emle Industries, Inc. v. Patentex, Inc., 478 F.2d 562, 571 (2d Cir.1973). Rebuttal evidence must therefore focus on “the scope of the legal representation” involved in each matter “and not on the actual receipt of ... information.” Westinghouse Electric Corp., 588 F.2d at 224.
By announcing an approach that deems transactions substantially related if the former government attorney may have had access to any information that could be useful — not just legally relevant — in the later transaction, and by prescribing a methodology for determining when the burden of producing rebuttal evidence shifts to the attorney, we have broadened the scope of the “substantially related” test for revolving door purposes (as compared with the Westinghouse Electric Corp. approach).
F.
Before addressing the merits, we believe it is important to discuss the approach suggested by the helpful presentation of our amicus curiae, the Legal Ethics Committee of the District of Columbia Bar.
Amicus’ suggested approach for determining whether transactions are substantially related is, in many respects, similar to the methodology we adopt today. Focusing on the context of the present case, amicus initially provided a three-factor test: “where transactions pertain to a single objective and involve the same property and the same party, public concerns about the fair administration of justice usually will support a determination that the transactions are part of the same matter.”
While acknowledging that the meaning of the “single-objective” factor is "not self-*51evident,” amicus stressed that this concept was devised to provide a “flexible factor” in the analysis “that permits a realistic assessment of reasonable public perception.” Thus, “[gjiving meaning to the phrase will require the Court to take into account each situation’s facts (too numerous and variable to identify in advance) and weigh them in light of the concerns to which the Rule is addressed and the potential occasions for abuses or improprieties which it seeks to prevent.”
As to this case — contrary to the dissenters’ implication — amicus did not specifically opine. Amicus left it to this court to apply the suggested test to the facts. Ami-cus added, however, that the transactions “need not all involve parking to constitute the same ‘matter,’ ” but they “do not involve the same ‘objective’ ... if the most specific common purpose which can be said to underlie them is the general economic development of a property or project.”
In further aid of the analysis, amicus stressed that “[e]ven where transactions involve the same party, same property or project and the same objective, ... certain facts, singly or in combination, may indicate that the transactions are not part of the same ‘matter.’ ” For example, “[p]ublic concerns would be less justifiable where the former government attorney served in an agency or office not involved in or concerned with the subsequent proceeding.” Moreover, “[t]he passage of an extended period of time should suggest that allegedly ‘substantially related’ transactions did not involve the same matter.” Finally, a “former government attorney should also be free to present facts indicating that he or she did not learn information having special usefulness to his or her subsequent private client.”
Amicus thus makes its three-factor test rebuttable. When viewed in light of this further refinement, the three-factor test appears to serve much the same function as the prima facie standard set forth above in Part HE, supra. The attenuating circumstances suggested by amicus can negate the existence of a substantial relationship, even where all three factors in the initial test are met. We therefore recognize a distinct parallel between the methodology we adopt for determining whether two transactions are substantially related and the approach advocated by amicus.
Amicus suggests, however, that it formulated its objective, three-factor approach — which may be modified by reference to attenuating circumstances — because of the following belief: an exclusive focus on whether the former government attorney may have had access to information in the first case that could be useful in the second one is not responsive enough to the multiple concerns created by the revolving door, such as the possibility that a government attorney, with an eye to future private employment, might not vigorously represent the government or might otherwise show favoritism to private parties.
Our disagreement with amicus’ approach is twofold. First, as explained in Part IIC and D, supra, the only concerns about the revolving door that properly can be reached by a “substantially related” test under DR 9-101(B) — in contrast with the total ban required by § 207(c) of the Ethics in Government Act of 1978, supra —are concerns about the potential misuse of government-developed information from a previous matter. Amicus’ other revolving door concerns, not related to information flow, are directed at appearances attributable to government service without a demonstrable, prejudicial relationship to an earlier government transaction. The very purpose of § 207(c) of the 1978 Ethics Act is to deal with such appearances of impropriety — and the realities they may reflect — for a period of one year from leaving government, even though no related transactions are identified. As indicated earlier, we perceive no basis for incorporating that broader purpose into the more limited DR 9-101(B) proscription against participating in substantially related matters — a proscription (we emphasize again) that, unlike § 207(c), does not have a prescribed time limit, see *52General Motors Corporation v. City of New York, 501 F.2d 639, 650 n. 21 (2d Cir.1974), and thus would completely shut the revolving door.
Second, the “single objective” criterion is too vague and wooden. The suggestion that, in order to constitute substantially related matters, the transactions at issue here need not all involve parking but should not be deemed related (sufficient to reflect a single objective) if the most specific common purpose is general economic development, does not take one far enough. If, for example — as we would conclude in this case, see infra Part III & n. 28 — the most specific common purpose is general economic development of the property, that should not preclude disqualification if former government counsel did have access to information from the earlier transactions that might be useful in representing Carr.
In applying our own methodology, however, we do agree with amicus that when there has been a series of transactions involving the same parties, the same property, and similar (not necessarily single) objectives, the factual contexts are likely to overlap sufficiently that the party who moves for disqualification under DR 9-101(B) will have established a prima facie case, even though the technical legal issues themselves are different. See supra Part HE. A look at the realistic objective of each transaction in these circumstances — a synthesis of the facts and legal objectives — will usually lead the court to conclude that an improper flow of information is likely. In the present case, for example, we are satisfied that the three land use transactions directed at the same property in the unique, relatively small CR zone, involving Oliver T. Carr and the District of Columbia government in each instance, provide a sufficient factual overlap for a reasonable person to infer that Iverson Mitchell and C. Francis Murphy, while attorneys for the District, may have had access to information from the height litigation and the air rights condominimum discussions that could be legally relevant to, or otherwise useful in, the special exception case at issue here. Accordingly, the burden of producing evidence to rebut this inference must be shifted to Mitchell and Murphy— and thus to their law firm, Wilkes & Artis.
III.
We turn now to the BZÁ proceedings— first, to our scope of review and, then, to the merits.
A.
Scope of Review
This court is to determine, as a matter of law, whether the transactions are “substantially related” and thus the same “matter.” But we are bound to do so on the basis of facts found by the BZA — properly reflecting our prescribed methodology — unless they are not “supported by and in accordance with the reliable, probative, and substantial evidence.” D.C.Code § 1-1509(e) (1981). “If there is substantial evidence to support the Board’s finding, then the mere existence of substantial evidence contrary to that finding does not allow this court to substitute its judgment for that of the Board.” Spevak v. District of Columbia Alcoholic Beverage Control Board, 407 A.2d 549, 554 (D.C.1979); accord Haight v. District of Columbia Alcoholic Beverage Control Board, 439 A.2d 487, 495 (D.C.1981); see Jameson’s Liquors, Inc. v. District of Columbia Alcoholic Beverage Control Board, 384 A.2d 412, 418 (D.C.1978).
BZA Proceedings
The BZA properly placed the burden of persuasion on petitioner Brown, the party who moved for disqualification, and petitioner presented evidence to support his allegations that the matter before the Board was substantially related to the two earlier matters. To rebut petitioner’s argument, intervenors presented seven witnesses, a number of sworn affidavits, and numerous documentary exhibits. Moreover, although petitioner has argued both to the *53BZA and to this court that he was denied access to certain materials and that information relevant to his case was not placed before the Board, the record does not reflect that petitioner was improperly denied discovery of any information for which he made a timely request, or that he attempted to call any witness or introduce any evidence that was improperly excluded. Accordingly, we conclude that the factual findings of the BZA after this hearing must stand if supported by substantial evidence.
Although Oliver T. Carr’s property in the West End CR Zone is the setting for each transaction, the BZA found that “[njeither the same facts, events, nor transactions were at issue in the three proceedings,” and that “the issues presented by the special exception are in no way connected to the height litigation or the opinion concerning the air rights condominium.”19 The BZA, moreover, spoke directly to the “critical” concern of the “substantially related” test — as we expressed it on remand of Brown I, supra note 16 — finding “no information present in the two earlier proceedings which would have aided the applicant in the subject [special exception] cases before the Board.” Decision, January 7, 1981, supra note 19; see Westinghouse Electric Corp., 588 F.2d at 225; Nyquist, 590 F.2d at 1247-48 n. 1 (Mansfield, J., concurring).
The dissenters would discard the BZA ruling substantially because, they say, the last sentence of finding/conclusion 25 —“Nor does any common core of relevant facts or principles render the matter identical” — applies the “wrong ultimate legal test.” Post at 66. We disagree. In the first place, that statement does not negate the other BZA factual findings, see supra note 19, supported by substantial evidence, that are relevant to applying the substantially related test; at worst it is superfluous. Second, on appellate review, application of the law to the facts, using the substantially related test, is ultimately for this court, not for the BZA. The dissenters do not dispute that. Finally, it is unfair, as well as irrelevant, to fault the BZA for saying in one sentence, amidst pages of findings, that the matters at issue are not “identical.” On remand, without referring to the substantially related test, this court in Brown I, 413 A.2d at 1282, asked the BZA to determine whether the special exception proceeding was the “same matter” as the two previous ones. In fact, we used that terminology throughout the opinion. Id. at 1281-84. In findings 25-27 the BZA, too, consistently used that terminology. More than likely, in reviewing our opinion and following our remand order, the BZA intended the concepts of “same” or “identical” matter to be synonymous, embracing the traditional, substantially related test that is embedded in the caselaw (cited in the division opinion) and applied here. But, even if the BZA did not apply the substantially related test, its findings are explicit enough and sufficiently supported by record evidence to permit this court to do so. In short, we perceive no basis for rejecting the BZA’s factual findings be*54cause of one sentence that arguably clouds the BZA’s legal conclusion — a conclusion that is ultimately for this court to make.
B.
The Height Litigation
We address, first, Carr’s 1975 litigation challenging the building height limitation on his West End property. Carr v. District of Columbia Zoning Commission, Civ. Action No. 4122-75 (1975).20 Former Assistant Corporation Counsel Iv-erson Mitchell, now one of intervenor Carr's counsel, represented the Zoning Commission. Carr successfully alleged that a 60-foot height limitation imposed by the Zoning Commission on buildings in the West End within 220 feet of Rock Creek Park (as compared with the 90-foot limitation in the rest of the CR zone) was arbitrary and capricious and thus an unconstitutional taking of his property. As a result, the usable floor-area ratio (FAR) for Carr’s property was increased from approximately 4.5 to 6.0, thereby permitting Carr to plan a larger building or buildings there.21 The height litigation accordingly achieved Carr’s objective of increasing the allowable rental space.
It is important to note that this litigation did not reflect or portend any particular type of development or parking arrangement. An increase in the FAR, while increasing rentable space as of right, has no direct bearing on whether the property can be developed for commercial or residential purposes. Nor, as to residential development, does an increased FAR have a direct relationship to the number of permitted parking spaces. The number of off-street residential parking spaces permitted as of right is directly related not to FAR but to the number of dwelling units — a maximum of two spaces per three units. D.C. Zoning Regs. § 4505.1 (1982).22 An increased FAR will either permit more dwelling units of the size originally contemplated or allow the same, or even a smaller, number of units if designed to be more luxurious, and thus larger, than initially planned. Accordingly, an increased FAR bears no necessary or direct relationship to the number of parking places eventually permitted as of right — or by special exception — because FAR does not necessarily dictate the number of dwelling units.
This is not to say that an FAR increase is unlikely to result in additional dwelling units and related parking spaces; more of*55ten than not it probably will. The relevant point, however, is twofold. First, there is no way one can say with reasonable certainty that in 1975 the height litigation, premised only on constitutional issues, had a direct bearing on the number of dwelling units and parking spaces to which Carr would be entitled. Developmental choices were still his to make, albeit with greater flexibility after he won the lawsuit. The dissenters are simply wrong in asserting, post at 61, that the height litigation concerned “the Westbridge,” i.e., the particular residential building Carr elected to develop much later, after winning the height litigation and aborting a different, mixed use air rights condominium proposal for the property.
Second, additional dwelling units automatically permit additional parking spaces — two spaces for every three residential units added. See supra note 22. The question of a special exception for still more parking spaces is wholly separate from the increased number permitted as of right as the number of dwelling units increases. The dissenters overlook this point, and thus improperly tie the height litigation automatically to the later special exception proceeding, when they say that, having previously “obtained an increase of some three stories for the building, this created a related need for more parking spaces in the building.” Post at 63; see post at 68. Because the height litigation did not alter the ratio of parking spaces to residential units permitted as of right, it did not create or otherwise affect the “need for more parking spaces.” There is a “need for more parking spaces” by way of a special exception only if the increased number permitted as of right — as an indirect result of the height litigation— proves insufficient for the particular project eventually planned. At the time of the height litigation this additional need was anything but clear, especially because the particular development eventually built — the Westbridge — was not yet contemplated, so far as we can tell.
We elaborate these implications of the height litigation, as well as our response to the dissenters’ analysis, to show that, in the absence of evidence — and there is none — that Mitchell may have been privy to information somehow relating it to Carr’s specific plans for the property and the District’s likely response, it does not appear that increasing the FAR would have had any relationship to a later special exception case concerning off-street parking at a development eventually planned for the same property. The BZA found no such relationship following remand of Brown I: “Nothing in the record herein demonstrates that any of the issues in the height litigation related to the subject of parking.” Findings 118. The BZA emphasized that “[t]he sole issue was the sixty foot height restriction and there was no reference to parking issues.” Findings II9. Most significantly, the BZA found that “no information” available to Mitchell from the height litigation “would have aided” Carr in the special exception case. Findings 1127, supra note 19.23
*56We see no basis for disturbing these findings; they are supported by substantial evidence. The record shows that the Zoning Commission imposed the height limitation on buildings adjacent to Rock Creek Park for aesthetic reasons, not because of a desire to limit traffic and related parking. The record also shows that, as a result of the trial court’s striking the height limitation, Carr was entitled to an increased FAR. But the record amply supports the BZA’s finding that the effect of the litigation on the eventual number of dwelling units and related parking spaces — as we elaborated above — was indirect and thus “coincidental.” Findings ¶ 27, supra note 19. Furthermore, in view of the fact that Carr proffered a mixed use air rights condominium proposal to the District government a few months after the height litigation, it is extremely unlikely that at the time of the height litigation Mitchell could have been privy to information about Carr’s eventual, wholly residential project in the West End: the Westbridge.
The Air Rights Condominium Proposal
Next, is the air rights condominium proposal. The October 24, 1975 letter from Carr’s attorney at that time, see supra note 20, to then Corporation Counsel Francis Murphy (now with Wilkes & Artis) read in relevant part as follows:
Dear Mr. Murphy:
Our firm represents Oliver T. Carr, Jr., who desires to develop the Sealtest Dairy Site at 26th and Pennsylvania Avenue, N.W. for residential, commercial and office uses under the new CR zoning. On October 21, 1975, representatives of Mr. Carr had a preliminary discussion with regard to the proposed development with Messrs. Louis Robbins, Iverson Mitchell, and Semi Feuer of your office, together with Messrs. Kirk White and Steve Sher of the Municipal Planning Office to acquaint them with the proposed development and mixed uses, and to request an opinion from the Corporation Counsel that the building complies with the new CR Zoning Regulations and Condominiums Laws of the District of Columbia. The purpose of this letter is to formally request such an opinion from the Corporation Counsel and to outline the facts involved....
It is our opinion that since we are building one building on one lot and the legal title is in one ownership that the proposed building meets all of the requirements of the CR zoning. More particularly, (i) that no rear yard is required since the building fronts on three streets, 26th, Pennsylvania Avenue, and M Streets; (ii) that the provision of private recreation space required for residential use is met by the provision of recreational space for the use of condominium owners over the roof of the first floor parking and retail areas; and (iii) parking limitations are met because the sum total of spaces do not exceed the maximum permitted for the uses contemplated. It is also our opinion that the building will continue to satisfy CR zoning requirements when condominium declaration is filed because of the covenants and easements described below. [Emphasis added.]
We would appreciate an opinion confirming that the proposed project does meet the CR zoning requirements conceptually, contingent upon the actual amount of various kinds of space being adequate and verified. In the event there is any problem, of which we are not aware, we would appreciate it if you would contact us so that we may attempt to resolve the problem.
In the first place, unlike the height litigation, the air rights condominium proposal would not have affected the amount of rentable space and related parking places permitted as of right after the height litigation. The FAR restrictions on rentable space, see supra note 21, as well as the zoning regulations applicable to parking, see supra note 22, for a building constructed on air rights do not differ from those applicable to a building owned in fee simple.
*57Furthermore, two witnesses testified without contradiction that parking in no way was at issue in the air rights condominium proposal. William Smith, the author of the letter and Carr’s trial counsel in the height litigation, see supra note 20, testified at the BZA hearing, explaining the reference to parking as follows: “I was saying that in our opinion, this building, this concept we had, would meet all the CR zoning requirements. Therefore, assuming that we met the zoning requirements, they were to go ahead and give us an Opinion as to whether or not an air rights condominium would be legal under the then-existing condominium statute. That was the only reason I referred to the parking.” Robert Carr, a vice president of the developer, explained the reference in these terms: “I don’t think there was any definition then of the precise number of parking spaces that were to be utilized by either the commercial or residential uses. I think that all this says is that it was the intention of the firm to comply with the parking levels set for zoning.”
The BZA, which had the opportunity to observe the witnesses, accepted this explanation, finding that “[t]he October meeting and letter dealt solely with the concept of an air rights condominium. Neither the meeting nor the letter dealt with or had any relation to parking.... Parking was not an issue in ... the condominium question.” We see no other plausible interpretation to give the words of the letter, and petitioner has offered none.24 Nor do we perceive any basis for upsetting the BZA’s finding that no information available to Murphy and Mitchell at the time of this transaction would have aided Carr in the special exception case. Decision, January 7, 1981, supra note 19.
The Special Exception for Additional Parking
There is, finally, the present case: an application for a special exception to permit additional, below grade parking spaces for the Westbridge residential development Carr eventually built. As noted earlier, CR zoning regulations require a developer to provide a minimum of one parking space for every six dwelling units and permit the developer to provide a maximum of two spaces for every three units. D.C. Zoning Regs. § 4505.1 (1982), supra note 22. The BZA may grant a special exception, permitting parking in excess of the maximum, if: (1) the proposed parking is indoor, id., § 4502.321; (2) the entrances and exits to the parking spaces are not within 25 feet of a street intersection or within 12 feet from the center line of an alley, id., §§ 4502.322, 7402.12; (3) “[s]uch parking shall not result in dangerous or otherwise objectionable traffic conditions, and the present character and future development of the neighborhood will not be adversely affected,” id., § 4502.323; and (4) “[s]uch parking is reasonably necessary and convenient to uses on the same lot or in the vicinity.” Id. § 4502.324.25
The application before the BZA would allow Carr to add 45 below-grade parking spaces to the West End development, creating a one-to-one ratio of spaces and dwelling units. Unlike the height litigation with the resulting increase in FAR, the special exception proceeding cannot be characterized as an attempt to increase the rentable space on Carr’s property. The FAR regulations do not restrict the amount of renta-ble space that may be added to a building below grade, see supra note 21; a builder may add as much space below grade as he or she chooses. Thus, the parking space exception, if granted, would not have affected the amount of rentable space avail*58able at the Westbridge; it only would have authorized Carr to use more of his rentable space below grade for parking.
On remand of Brown I, the BZA found the regulations’ criteria satisfied and granted the application in its order of May 17, 1978, concluding that additional below grade parking would ameliorate traffic conditions in the vicinity of the Westbridge.26 As noted earlier, see supra note 19, the BZA expressly found that no facts or issues in this special exception case were in any way connected with the earlier building height and air rights condominium transactions, and that no information which may have been available to Mitchell and Murphy from these previous transactions would have aided Carr in the special exception case. Given the decidedly different legal issues in each transaction and the testimony and exhibits of record as to each, we conclude that substantial evidence of record supports these findings.
Summary
Although the height litigation facilitated an increase of rentable space, indirectly permitting construction of a building with a larger number of dwelling units and related parking spaces than Carr otherwise probably would have planned, the maximum number of parking spaces remained fixed by the zoning regulations at a ratio of two spaces for every three units. Thus, the height litigation was not related to Carr’s later objective, announced in the special exception proceeding, of obtaining one parking space per residential unit. Nor was the aborted mixed use air rights condominium proposal — which pertained neither to the amount of rentable space nor to parking — in any way related to Carr’s application for an increase in off-street parking at the later-conceived, residential Westbridge development. Finally, because the special exception case concerned only parking, it was not related to Carr’s earlier objectives of increasing rentable space through the height litigation and seeking an opinion on the legality of an air rights condominium in the CR zone.
The dissenters reject this analysis primarily because of a faulty premise: that all three matters — height litigation, air rights condominium proposal, and special exception case — concerned the “same building (the Westbridge).” Post at 61; see post at 61, 63, 66, 68. That is plainly not true, as the dissent itself acknowledges in two footnotes. Post at 61 n. 4, 66 n. 12. The same property is involved, but we have no evidence that the Westbridge, and Carr’s desire to maximize the number of parking spaces there, was in anyway related to the two earlier proceedings. Indeed, the intervening air rights condominium proposal is clear evidence that the Westbridge, as such, was not involved in the two earlier proceedings. In short, the dissenters posit “an uncomplicated case,” post at 61, that mischaracter-izes what happened27 and then proceed to *59attack the majority opinion for not dealing, in effect, with the dissenters’ own hypothetical set of facts.
IV.
We conclude that the BZA analysis is correct: Carr’s application to the BZA for a special exception for additional, below grade parking at the residential West-bridge development — a matter not increasing rentable space — is not substantially related, within the meaning of DR 9-101(B), to (1) the earlier discussion/correspondence about a mixed use air rights condominium proposal on the same property (which did not concern rentable space or parking), or (2) the earlier height litigation establishing on constitutional grounds increased FAR, and thus more rentable space, on the same property — with no direct relationship to permitted off-street parking.28
Some members of the general public, not attuned to the revolving door debate, may wonder why former government attorneys — who negotiated or litigated with a developer on behalf of the public in the implementation of a novel zoning district— should be permitted, after leaving the government, to bring their expertise to that developer as his lawyers for the continuing effort to exploit that zoning for private gain. We believe, however, that properly informed of the countervailing concerns, the public would find the revolving door rules — protecting against prejudicial use of government information — palatable. While it presumably is true that other attorneys in the developer’s law firm could have handled the special exception case, with the former government attorneys properly “screened,” DR 9-102, we have resolved that, for matters not substantially related to previous representation of the government, such insulation is not necessary. This court should expect no more than what the rules require. On this record, the revolving door rules permit Wilkes & Artis to represent intervenors in this case.
Affirmed.
. In 1978, when petitioners moved to disqualify intervenors’ counsel, DR 9-101(B) provided:
A lawyer shall not accept private employment in a matter in which he had substantial responsibility while he was a public employee.
At that time, the Code of Professional Responsibility did not define "matter.”
In 1982, this court amended DR 9-101(B) to read:
A lawyer shall not at any time accept private employment in connection with any matter in which he or she participated personally and substantially as a public officer or employee, which includes acting on the merits of a matter in a judicial capacity.
See "Revolving Door," 445 A.2d 615, 617 (D.C.1982) (en banc) (per curiam). We defined "matter" as follows:
“Matter” includes any judicial or other proceeding, application, request for a ruling or other determination, contract, claim, controversy, investigation, charge, accusation, arrest or other particular matter involving a specific party or parties.
Id. at 618. The new rule combined former DR 9-101(A) and (B) into one disciplinary rule without any intended substantive change. Thus, although we decide the present case under the old rule (since the 1982 amendments have prospective effect), the result would be the same if the new rule were applicable.
For the record we note that on August 2, 1983, the American Bar Association’s House of Delegates gave final approval to new Model Rules of Professional Conduct, including Rule 1.11 on "Successive Government and Private Employment." On September 12, 1983, this court ordered that these Model Rules "shall not become effective in the District of Columbia pending further order of this court” after comments and recommendations by the District of Columbia Bar and other interested bar associations and persons.
. The BZA found:
There was no screening [at Wilkes & Artis] until approximately July of 1980, when
*41screening procedures were first implemented. Therefore, Messrs. Mitchell [and] Murphy were not screened by the Wilkes and Artis law firm from participating in the subject BZA application No. 12531. The Board finds that, while the procedures of the firm of Wilkes and Artis for screening new employees left much to be desired, both Messrs. Murphy and Mitchell were effectively screened as a practical matter with respect to participation in the subject special exception. [Emphasis added.]
Because of the express findings that there were no screening procedures until July 1980 and that Mitchell arid Murphy "were not screened” from participating in the special exception case, the BZA’s conclusion that "Murphy and Mitchell were effectively screened as a practical matter” is a non sequitur and thus clearly erroneous.
. At the hearing on remand on October 8, 1980, petitioners' counsel explored alleged contacts in 1973 between Corporation Counsel Murphy and attorneys from Wilkes & Artis (representing Carr) concerning legislative creation of the CR Zone. See post at 62. On cross-examination, Murphy testified: "I have no independent recollections. I’m not saying I didn’t meet with them but I don’t recall it.” On October 23, 1980, petitioners' counsel filed a motion to reopen the record and to conduct a further hearing to explore these alleged contacts and other matters. As exhibits, counsel attached copies of letters from counsel for Carr (other than Wilkes & Artis) referring to meetings between Norman Glasgow of Wilkes & Artis and Murphy addressing, among other things, "four approaches to obtaining this new [CR] zoning." See post at 62. On November 10, 1980, Steven E. Sher, Executive Director of the BZA, wrote petitioners’ counsel that his motion had been denied "on the grounds that the Motion contained no issues or evidence that the Board had not entertained before and that all parties had sufficient time to present their cases and cross-examine.” Apparently, the BZA concluded, after two hearings, that it was late in the day for petitioners to try to introduce still another transaction al-
legedly related to the special exception case. Nonetheless, in its final order of November 12, 1981, the BZA acknowledged the exhibits filed with petitioners’ motion and stated in finding 18: "The Board finds that, even assuming those contacts, there is no relationship, factual or legal, between the public hearings on the CR zoning issues and the subject special exception."
The dissenters use the letters concerning creation of the CR zone, attached to petitioners’ motion to reopen, as though they reflect a fourth transaction at issue in this case — a transaction that was not part of the initial proceeding and was not at issue on remand. But even if we assume that creation of the CR zone itself was at issue, it was not substantially related to the application for a special exception. From all that appears of record (including the letters proffered with petitioners’ motion), the facts and issues germane to processing the CR zoning text amendment through the Zoning Commission in 1973-74 are entirely different from those pertinent to advocating a special exception to that zoning, under other regulations, before the BZA in 1977-78. Aside from saying that each "affects parking” on the Carr property in the West End, which creates an "appearance of impropriety,” petitioners have proffered nothing to show the critical condition required for finding a substantial relationship between the two transactions: that information (other than general agency expertise) apparently available to Murphy during the CR zoning period may have been relevant to issues in the special exception case. See infra Part IIB.
Even if there were doubt here, the proper disposition would not be to disqualify interve-nors’ counsel but to remand to the BZA for further proceedings as to whether creation of the CR zone itself is substantially related to the application for a special exception. This court cannot validly take letters attached to petitioners’ motion, not subject to objection or cross-examination, and use them as evidence for appellate court fact-finding, in the first instance, that a substantial relationship exists.
. In Riverfront Parks, we cited with approval the definitional language of the American Bar Association characterizing a "matter" as “ ‘a discrete and isolatable transaction or set of transactions between identifiable parties_Id. at 1188 (quoting ABA Comm, on Professional Ethics and Grievances, Formal Op. 342 at 6 (1975)) (emphasis added). By referring to a “set of transactions," we implicitly adopted the "substantially related” test. Our definition of "matter" under the 1982 amendment of DR 9-101(B), see supra note 1, is intended only to identify the types of transactions embraced by that term; it does not affect the "substantially related” test.
. In announcing the rule, the court explained that it would not inquire as to whether there actually had been a breach of the confidential relationship:
I hold that the former client need show no more than that the matters embraced within the pending suit wherein his former attorney appears on behalf of his adversary are substantially related to the matters or cause of action wherein the attorney previously represented him, the former client. The Court will assume that during the course of the former representation confidences were disclosed to the attorney bearing on the subject matter of the representation. It will not inquire into their nature and extent. Only in this manner can the lawyer’s duty of absolute fidelity be enforced and the spirit of the rule relating to privileged communications be maintained.
T.C. Theatre Corp., 113 F.Supp. at 268-69. Other courts agree. "In order to grant a disqualification motion, a court should not require proof that an attorney actually had access to or received privileged information while representing the client in a prior case.” Government of India v. Cook Industries, Inc., 569 F.2d 737, 740 (2d Cir.1978). Rather, the court need only ask " 'whether it could reasonably be said that during the former representation [that] attorney might have acquired information related to the subject matter of the subsequent representation.' " Westinghouse Electric Corp. v. Gulf Oil Corp., 588 F.2d 221, 225 (7th Cir.1978) (citation omitted) (emphasis added). Thus, when a party seeking disqualification carries its burden of persuading the factfinder that .two matters, handled by the same counsel, are substantially related, there is an irrebuttable presumption that counsel received information during the first representation that is relevant to the second.
The foregoing analysis speaks in terms of a single lawyer involved in two matters found to be substantially related. When, instead, a law firm is involved in either of two substantially related matters, questions sometime arise concerning the extent to which information has been shared among individual attorneys within the firm. For example, when a firm has provided representation in the first of two related matters, a court may have to determine whether an individual attorney who has since left the firm should be permitted, in effect, to switch sides by representing a party in the second matter adverse to his former firm’s client in the first matter. In this situation, courts have established a rebuttable presumption that an attorney has received confidential information during the first matter. Thus, disqualification will be required unless the attorney clearly shows that, while at the firm, he or she did not work on the case and was not otherwise in a position to gain access to confidential information related to the first matter. See Silver Chrysler Plymouth v. Chrysler Motor Corp., 518 F.2d 751, 754 (2d Cir.1975); see generally Liebman, The Changing Law of Disqualification: The Role of Presumption and Policy, 73 Nw.U.L.Rev. 996 (1979). Second, when an individual attorney has admittedly had substantial responsibility for the first of *43two substantially related matters and later joins a law firm that seeks to represent an adverse party in the second matter, a court will have to determine whether the presence of the new attorney at the firm requires disqualification of the entire firm. Again, in this private side-switching context courts have adopted a rebut-table presumption that knowledge is shared among firm members. Courts therefore require disqualification of the entire firm absent a showing that the new partner or associate has been effectively screened from participation in the second matter. See LaSalle National Bank v. County of Lake, 703 F.2d 252, 257-59 (7th Cir.1983); see generally Peterson, Rebuttable Presumptions and Intra-Firm Screening, 59 Notre Dame L.Rev. 399 (1984).
. In "Revolving Door" we adopted DR 9-101(B), see supra note 1, precluding private employment with respect to any "matter” in which the attorney "participated personally and substantially” while in government; and, in response to the related, "imputed disqualification” problem, we adopted DR 9-102, permitting a firm that hires a former government attorney to keep, or take on, such a matter if that attorney is properly screened from participating and sharing fees in it. 445 A.2d at 617. See Sierra Vista Hospital, Inc. v. United States, 226 Ct.Cl. 223, 639 F.2d 749, 753 (1981) (upheld denial of motion to disqualify law firm where former government attorney at firm, himself disqualified, was entirely screened from participation in case); Armstrong v. McAlpin, 625 F.2d 433, 445 (2d Cir.1980) (en banc) (same), vacated on other grounds, 449 U.S. 1106, 101 S.Ct. 911, 66 L.Ed.2d 835 (1981) (disqualification motion not appeala-ble under 28 U.S.C. § 1291); Kesselhaut v. United States, 214 Ct.Cl. 124, 555 F.2d 791, 793 (1977) (same).
. The “rule" adopted in Standard Oil thus permits a complainant to make use of two inferences in seeking to disqualify a former government attorney. 136 F.Supp. at 354. First, a showing of "a substantial relationship between the subject matter of a law suit and the matters in which the attorney represented his former *44client” gives rise to "an inference that confidential information was reposed.” Id. Second, if the complainant shows that the challenged attorney’s government position provided access to materials substantially related to the second representation, even if the attorney did not handle the government case, the court will infer that the attorney actually gained personal knowledge of confidential information. Id.; see generally Kaufman, The Former Government Attorney and the Canons of Professional Ethics, 70 Harv.L.Rev. 657 (1957).
Under DR 9-101(B), the focus of the substantial relationship test is solely on the relationship between the subject matter of each representation at issue. Consideration of the attorney’s relationship to the earlier government matter— i.e., the attorney’s potential access to useful government-developed information — is relevant to the separate DR 9-101(B) inquiry into whether the earlier matter was one in which the attorney “participated personally and substantially” (or, under the pre-1982 version of the rule, "had substantial responsibility”). Because we conclude that there is no substantial relationship between the subject matters of each of the three representations at issue here (and hence no inference of useful information received), we need not address the “substantial responsibility” issue in this case.
. One court specifically has noted, however, that "the question of ‘side-switching,’ and of the conflict of interest which is almost certain to arise when counsel changes sides, is addressed by Canon 4 [Preservation of Confidences and Secrets of a Client] and not Canon 9 [Avoiding Even the Appearance of Impropriety].” General Motors Corporation v. City of New York, 501 F.2d 639, 650 n. 20 (2d Cir.1974). Nonetheless, courts commonly consider both ethical canons together, e.g., Board of Education v. Nyquist, 590 F.2d 1241, 1246 (2d Cir.1979); Westinghouse Electric Corp. v. Gulf Oil Corp., 588 F.2d 221, 224 (7th Cir.1978); NCK Organization Ltd. v. Bregman, 542 F.2d 128, 129 (2d Cir.1976). In these cases, the Canon 9 gloss — the concern about even an appearance of impropriety — is a significant reinforcement of the court’s typical view that, under Canon 4, disqualification does not depend upon proof of an actual breach of confidentiality. See supra note 5.
. At least one court considering side-switching from one private client to another has expressed a similar concern:
Both the lawyer and the client should expect that the lawyer will use every skill, expend every energy, and tap every legitimate resource in the exercise of independent professional judgment on behalf of the client and in undertaking representation on the client’s behalf. That professional commitment is not furthered, but endangered, if the possibility exists that the lawyer will change sides later in a substantially related matter.
Troné v. Smith, 621 F.2d 994, 998 (9th Cir.1980).
. See Developments in the Law: Conflicts of Interest, 94 Harv.L.Rev. 1244, 1434 (1981) (recognizing three purposes underlying DR 9-101(B): (1) "protecting confidentiality"; (2) “denying the attorney’s private client the unfair advantage of his attorney's earlier access to information gathered with the special powers and resources of the government”; and (3) “deterring the lawyer from compromising his official duties to advance employment interests in the same matter.”)
, As the Legal Ethics Committee of the District of Columbia Bar has noted with reference to DR 9-101(B):
[T]he rule is not worded so as to effectuate in all instances its stated purpose. For instance, there may be an appearance of professional impropriety in any instance where a lawyer, soon after leaving public employment, accepts compensation for representation of a private client who has benefited from decisions or recommendations made by the lawyer in his public capacity. This is true quite apart from whether the decisions or recommendations were made in the same “matter" in which representation was later undertaken.
Op. 26 (1977) (latter emphasis added).
.Until the adoption of 18 U.S.C. § 207(c) (1982), Congress had been content to risk whatever real or apparent improprieties there may be in these other four consequences of the revolving door, in order to assure the government’s ability to hire well-qualified lawyers and other employees. The assumption has been that the best lawyers, sooner or later, will want to join the more lucrative private sector, and that government cannot attract them in the first place unless they are relatively free to market their government experience.
Section 207(c) has no bearing on the present case because Murphy and Mitchell left the Corporation Counsel’s office to join Wilkes & Artis in 1976, before § 207(c) was enacted.
. Other commentators have recognized that DR 9-101(B) "fails to address some potential abuses” of the revolving door. Developments in the Law, supra note 10, 94 HarvX.Rev. at 1437.
Although [DR 9-101(B) ] avoids actual abuse of authority in the matter itself, something further is needed to guard against problems of favoritism and undue influence on the part of former high-ranking agency officials.
******
Concerns about the revolving door that relate more to undue influence and favoritism than to misuse of specialized knowledge are addressed by temporarily expanding disqualification to prohibit high-ranking agency officials from contacting their former agencies [i.e. by 18 U.S.C. § 207, as well as similar state statutes, prescribing mandatory “cooling off' periods for former government attorneys].
Id. at 1437, 1439; see id. at 1435-39.
Although "appearances” may be relevant to a decision under DR 9-101(B) — where those appearances arise from "the possible use of insider information," Brown I, 413 A.2d 1276, 1283 (D.C.1980) — DR 9-101(B) should not be stretched beyond its stated limits in an effort to remedy appearances of impropriety that exist irrespective of whether the former government attorney was involved in a previous related matter. See generally O’Toole, Canon 9 of the Code of Professional Responsibility: An Elusive Ethical Guideline, 62 Marq.L.Rev. 313, 326-33, 342-43 (1979) (describing "moderate” approach to attorney disqualification under Canon 9). Any attempt to use DR 9-101(B) to address concerns that are beyond the scope of the plain language of the rule will serve only to heighten suspicions about the integrity of the legal system, rather than bolster public confidence. See Woods, 537 F.2d at 813 ("An overly broad application of Canon 9 ... would ultimately be self-defeating.”).
. When two matters are so unrelated that a review of their factual contexts reveals no reasonable likelihood that a government attorney with substantial responsibility in the first had access to information that would be useful in the second (about the parties, the facts, or the peculiarities of the law developed), it is difficult to imagine how the first matter could serve as an intended vehicle for developing the second.
Consider, for example, a Department of Justice lawyer who investigates General Motors for possible antitrust violations. Conceivably, he or she could learn something of value for use later, as a private lawyer, in a products liability case either suing or defending General Motors. Standing alone, however, the factual connection between the two claims would be too tenuous to support an inference of an intent to prepare for the later case through the use of government-acquired information. Put another way, the lack of overlap between the claims makes it unlikely that the attorney channeled government resources into the antitrust investigation in the hope of learning something that would be useful in a later products liability action.
. While in the private side-switching cases the courts typically have asked "whether it is reasonable to infer that the confidential information allegedly given would have been given to a lawyer representing a client in those matters,” Westinghouse Electric Corp. v. Gulf Oil Corp., 588 F.2d 221, 225 (7th Cir.1978) (emphasis added), in a "revolving door” case implicating the second or third category of abuse, confidentiality of the information is not the critical aspect.
. As we instructed the BZA on remand in this case: "The critical test must be whether the government attorney in the former zoning proceeding had the opportunity to gather information he could not otherwise have gained which he could then use on behalf of the private party in the later proceeding. The information of concern is not general data, ... [but rather] specific information not available to the public." Brown I, supra note 13, 413 A.2d at 1283.
If a party who seeks disqualification need not show even a reasonable possibility that an actual impropriety, based on the likely abuse of government-developed information, has taken place, we would invite disqualification motions based entirely on hypothesis and innuendo. We would encourage time-consuming motions made for purely tactical reasons, at great cost to litigants and the courts. Board of Education v. Nyquist, 590 F.2d 1241, 1246 (2d Cir.1979); Allegaert v. Perot, 565 F.2d 246, 251 (2d Cir.1977); see W.T. Grant Co. v. Haines, 531 F.2d 671, 677-78 (2d Cir.1976). We would encourage litigants to convert lawsuits into disciplinary inquiries when there is no reasonable possibility that the underlying proceeding is tainted, and thus would permit litigants, unfairly, to avoid the merits of a case by attacking opponent's counsel instead. See Freeman v. Chicago Musical Instrument Co., 689 F.2d 715, 722 (7th Cir.1982) (disqualification motions “should be viewed with extreme caution for they can be misused as techniques of harassment”).
. In making out a prima facie case, a complainant need not specify any particular information or material b.elieved to be relevant to both of the related transactions. A showing of overlapping factual contexts may be sufficient to create an inference that the government developed information during the first matter which could be useful in the later private matter, and thus that the two matters are substantially related. See Westinghouse Electric Corp., 588 F.2d at 224 ("the determination of whether there is a substantial relationship turns on the possibility, or appearance thereof, that confidential information may have been given to the attorney.... [I]t is not appropriate for the court to inquire into whether actual confidences were disclosed.”).
. To rebut a complainant’s prima facie showing of substantial relationship, the former government attorney must produce evidence elaborating on the nature of the two matters so as to make it “clearly discernible” that the issues involved are unrelated and that the court should not infer the existence of useful government-developed information. Westinghouse Electric Corp., 588 F.2d at 224. If the attorney is unable to produce such evidence, the complainant will have met the burden of persuasion on the substantial relationship test_ and disqualification can be avoided only on a different ground: the attorney must show that he or she did not “participate] personally and substantially” in the first matter. DR 9-101(B); see supra notes 1 and 7; cf. supra note 5.
. More specifically, we cite three paragraphs of the BZA’s decision of January 7, 1981:
25.The Board finds that the issues presented by the special exception are in no way connected to the height litigation or the opinion concerning an air rights condominium. None of the standards which the Board was required to apply in deciding the special exception have any bearing at all on the issues which were presented by the height litigation or the air rights condominium question. Neither the same facts, events, nor transactions were at issue in the three proceedings. Nor does any common core of relevant facts or principles render the matter identical.
26. The Board finds that the fact that the same property was involved is not a sufficient connection to create an identity of issues and render the three matters as the "same matter.”
27. The Board finds that the coincidental fact that the result of the decision by the Superior Court allows a larger development and thus more parking on the site is also not sufficient to create a “same matter” connection. The standards for the special exception have to be met, and the Board finds no information present in the two earlier proceedings which would have aided the applicant in the subject cases before the Board.
. The BZA found that intervenors’ present counsel (Wilkes & Artis) “had no role in” the height litigation. The firm of Stohlman, Beuc-hert, Egan and Smith, Carr’s general counsel, represented Carr in both the height litigation and the air rights condominium discussion.
. The floor-area ratio is a "figure which expresses the total gross floor area as a multiple of the area of the lot. This figure is determined by dividing the gross floor area of all buildings on the lot by the area of that lot." D.C.Zoning Regs. § 1201 (1982) (emphasis in original).
The term gross floor area means ”[t]he sum of the gross horizontal areas of the several floors of all buildings on the lot; ... [but] shall not include cellars.” Id. A cellar, in turn, is defined as any area "the ceiling of which is less than four feet above the adjacent finished grade.” Id. Thus, any below grade area with a ceiling that is less than four feet above grade will not be included in a calculation of the gross floor area and, accordingly, will not be included in the floor-area ratio or affected by restrictions on that ratio.
As applied, "[i]n the CR District the floor area ratio of all buildings and structures on a lot shall not exceed 6.0, not more than 3.0 of which may be used for other than residential purposes." D.C.Zoning Regs. § 4504.1 (1982) (emphasis in original).
.D.C.Zoning Regs. § 4505.1 (1982) provides in relevant part;
All buildings and structures shall be provided with offstreet parking spaces, as specified in the following parking schedule....
Parking Schedule
Use
Minimum Number
Maximum Number Spaces
Single family 0 1/dwelling unit
dwelling or flat Multiple 1/6 dwelling units 1/3 dwelling units
dwelling Multiple 1/6 dwelling units 2/3 dwelling units
dwelling
constructed as a
cooperative or
condominium
. In response to the concern about government attorneys looking ahead to private employment, the BZA added that it could not find "the litigation was not vigorously defended by the Corporation Counsel.” Findings ¶ 19. The record confirms that Mitchell capably conducted the District’s litigation effort. He defended the height limitation on the basis of the record developed before the Zoning Commission. He testified before the BZA that this strategy was consistent with the Corporation Counsel’s position "that the record must stand on itself, that the Court could not substitute its judgment for that of the Zoning Commission.” In the BZA proceeding, petitioner introduced no evidence to contradict Mitchell’s assertion that this was official Corporation Counsel policy; nor did petitioner introduce any other evidence to suggest that Mitchell was anything but zealous in his representation of the District of Columbia’s interests. Moreover, there is no possibility that Mitchell improperly diverted public funds for private gain. See General Motors Corp. v. City of New York, 501 F.2d 639, 650 (2d Cir.1974); Allied Realty of St. Paul, Inc. v. Exchange National Bank of Chicago, 283 F.Supp. 464, 469 (D.Minn.1968), aff’d, 408 F.2d 1099 (8th Cir.), cert. denied, 396 U.S. 823, 90 S.Ct. 64, 24 L.Ed.2d 73 (1969). The government’s position in the height litigation was wholly defensive.
. Moreover, there is nothing in the record to suggest that the number of dwellings and related parking spaces in the proposed air rights condominium would have been greater or fewer than the number in the Westbridge development that Carr ultimately constructed.
. The regulations also require the BZA to refer the application to the District of Columbia Municipal Planning Office “for coordination, review and report” before taking final action. D.C.Zoning Regs. § 4502.325.
. In particular, the BZA found:
13. The requested parking will be used as storage parking for the owners of the proposed condominium units to be erected as a part of the development project. The spaces will not be utilized by either commuters or others who wish to avail themselves of commercial parking in an intown area.
14. The applicant’s traffic expert testified and the Board finds that the proposed parking will not generate many trips or significantly increase traffic because of its nature as storage parking for residents of the building.
15. Parking provided at the ratio of one space per dwelling unit will keep the automobiles owned by the resident occupants of the proposed building off adjacent community streets and off other parking lots in the area, thereby diminishing traffic impact in the vicinity of the proposed building.
. The dissent states, post at 61:
Two attorneys were involved while in government with problems and litigation related to the construction of a building (the Westbridge) in the "West End” of Washington, D.C. Later, they both joined a law firm and proceeded to represent the same property owner, Mr. Carr, in a proceeding involving the same property and the same building4 in its final stages of construction.
4 By “same building” I mean the building constructed on the same site....
This characterization of the facts has two obvious flaws: (1) The two former government attorneys, Murphy and Mitchell, were never in*59volved with the Westbridge while in government; that particular project was initiated after they left. (2) The reference to "the same property and the same building in its final stages of construction" is plainly wrong. The Westbridge building is wholly separate from, and came altogether after, the aborted air rights condominium proposal. There simply was no building inherent in the air rights proposal, let alone in the earlier height litigation, with which the Westbridge can be equated and thus called the “same.” See post at 66 n. 12. Accordingly, the dissenters really proffer a twofold "same property owner/same property" test, not a threefold test.
. Clearly, the most specific single objective that embraces all three transactions is the general economic development of Carr’s West End property — not enough under amicus’ formulation to constitute disqualification under DR 9-101(B). More properly characterized, there are three, unrelated objectives: increased rentable space (height litigation), the legality of air rights ownership in the CR zone (mixed use condominium proposal), and increased off-street parking (special exception application).