This Rule governed the practice of law in the District of Columbia from January 1, 1991, through January 31, 2007. As of February 1, 2007, the Amended Rules took effect.
(a) While lawyers are associated in a firm, none
of them shall knowingly represent a client when any one of them practicing
alone would be prohibited from doing so by Rules 1.7, 1.8(b), 1.9, or
2.2; provided, however, that this paragraph shall not apply if an individual
lawyer’s disqualification results solely from the fact that the
lawyer consulted with a potential client for the purpose [of] enabling
that potential client and the firm to determine whether they desired
to form a client-lawyer relationship, but no such relationship was ever
(b) When a lawyer becomes associated with a firm, the firm may not knowingly represent a person in a matter which is the same as, or substantially related to, a matter with respect to which the lawyer had previously represented a client whose interests are materially adverse to that person and about whom the lawyer has in fact acquired information protected by Rule 1.6 that is material to the matter. The firm is not disqualified if the lawyer participated in a previous representation or acquired information under the circumstances covered by the proviso to paragraph (a) of this rule or by Rule 1.6(g).
(c) When a lawyer has terminated an association with a firm, the firm is not prohibited from thereafter representing a person with interests materially adverse to those of a client represented by the formerly associated lawyer during the association unless the matter is the same or substantially related to that in which the formerly associated lawyer represented the client during such former association.
(d) A disqualification prescribed by this Rule may be waived by the affected client under the conditions stated in Rule 1.7.
(e) A lawyer who, while affiliated with a firm, is made available to assist the Office of Corporation Counsel or the District of Columbia Financial Responsibility and Management Assistance Authority in providing legal services to that agency is not considered to be associated in a firm for purposes of paragraph (a), provided, however, that no such lawyer shall represent the Office of Corporation Counsel or the District of Columbia Financial Responsibility and Management Assistance Authority with respect to a matter in which the lawyer’s firm appears on behalf of an adversary.
Definition of "Firm"
 For purposes of the Rules of Professional Conduct, the term "firm" includes lawyers in a private firm, and lawyers employed in the legal department of a corporation or other organization, or in a legal services organization, but does not include a government agency or other government entity. Whether two or more lawyers constitute a firm within this definition can depend on the specific facts. For example, two practitioners who share office space and occasionally consult or assist each other ordinarily would not be regarded as constituting a firm. However, if they present themselves to the public in a way suggesting that they are a firm or conduct themselves as a firm, they should be regarded as a firm for purposes of the Rules. The terms of any formal agreement between associated lawyers are relevant in determining whether they are a firm, as is the fact that they have mutual access to confidential information concerning the clients they serve. Furthermore, it is relevant in doubtful cases to consider the underlying purpose of the Rule that is involved. A group of lawyers could be regarded as a firm for purposes of the Rule that the same lawyer should not represent opposing parties in litigation, while it might not be so regarded for purposes of the Rule that information acquired by one lawyer is attributed to another.
 With respect to the law department of an organization, there is ordinarily no question that the members of the department constitute a firm within the meaning of the Rules of Professional Conduct. However, there can be uncertainty as to the identity of the client. For example, it may not be clear whether the law department of a corporation represents a subsidiary or an affiliated corporation, as well as the corporation by which the members of the department are directly employed. A similar question can arise concerning an unincorporated association and its local affiliates.
 Similar questions can also arise with respect to lawyers in legal aid organizations. Lawyers employed in the same unit of a legal service organization constitute a firm, but not necessarily those employed in separate units. As in the case of independent practitioners, whether the lawyers should be treated as associated with each other can depend on the particular Rule that is involved, and on the specific facts of the situation.
 Where a lawyer has joined a private firm after having represented the government, the situation is governed by Rule 1.11. The individual lawyer involved is bound by the Rules generally, including Rules 1.6, 1.7, and 1.9.
 Different provisions are thus made for movement of a lawyer from one private firm to another and for movement of a lawyer from the government to a private firm. The government is entitled to protection of its client confidences, and therefore to the protections provided in Rules 1.6 and 1.11. However, if the more extensive disqualification in Rule 1.10 were applied to former government lawyers, the potential effect on the government would be unduly burdensome. The government deals with all private citizens and organizations, and thus has a much wider circle of adverse legal interests than does any private law firm. In these circumstances, the government’s recruitment of lawyers would be seriously impaired if Rule 1.10 were applied to the government. On balance, therefore, the government is better served in the long run by the protections stated in Rule 1.11.
Principles of Imputed Disqualification
 The rule of imputed disqualification stated in paragraph (a) gives effect to the principle of loyalty to the client as it applies to lawyers who practice in a law firm. Such situations can be considered from the premise that a firm of lawyers is essentially one lawyer for purposes of the Rules governing loyalty to the client, or from the premise that each lawyer is vicariously bound by the obligation of loyalty owed by each lawyer with whom the lawyer is associated. Paragraph (a) operates only among the lawyers currently associated in a firm. When a lawyer moves from one firm to another, the situation is governed by paragraph (b) or (c).
Exceptions in the Case of a Prospective New Client
 As indicated by the proviso in paragraph (a) of this Rule, the principle of loyalty diminishes in importance if the sole reason for an individual lawyer’s disqualification is the lawyer’s initial consultation with a prospective new client with whom no client-lawyer relationship was ever formed, either because the lawyer detected a conflict of interest as a result of an initial consultation, or for some other reason (e.g., the prospective client decided not to retain the firm). As provided by Rule 1.6(a), and Comment  thereunder, the individual lawyer involved in any such initial consultation is required to maintain in strict confidence all information obtained from the prospective client even if a client-lawyer relationship was never formed. That obligation may in turn cause the individual lawyer to be disqualified pursuant to Rule 1.7(b)(4) from representing a current or future client of the firm adverse to the prospective client because that lawyer’s inability to use or disclose information obtained from the prospective client may adversely affect that lawyer’s professional judgment on behalf of the current or future client of the firm whose interests are adverse to the interests of the prospective client.
 The individual lawyer of the firm who obtains information from a prospective client under the circumstances described in the proviso to paragraph (a) of this Rule is permitted by Rule 1.6(a) to disclose that information to other persons in the lawyer’s firm only to the minimum extent necessary to enable the firm to determine whether it may ethically accept the proposed representation, and if so, whether it desires to do so. For the reasons stated in paragraph , any such dissemination may necessarily cause additional individual lawyers of the firm to be personally disqualified from representing a current or future client of the firm adverse to the potential client. Nevertheless, as provided in Rule 1.10(a), the personal disqualification of individual lawyers is not imputed to the firm as a whole. Accordingly, any other lawyer in the firm who is not personally disqualified vis-à-vis the prospective client may represent a current or future client of the firm adverse to the prospective client.
 When a firm relies on the proviso in paragraph (a) to this Rule to avoid imputed disqualification of the firm as a whole, that firm must take affirmative stepsas soon as an actual or potential conflict is suspectedto prevent the personally disqualified lawyers from disseminating any information about the potential client that is protected by Rule 1.6, except as necessary to investigate potential conflicts of interest, to any other person in the firm, including non-lawyer staff. Conversely, the personally disqualified lawyers should not receive any confidences or secrets of the firm’s clients in the conflicted matter.
Lawyers Moving Between Firms
 When lawyers move between firms or when lawyers have been associated in a firm but then end their association, the fiction that the law firm is the same as a single lawyer is no longer wholly realistic. There are several competing considerations. First, the client previously represented must be reasonably assured that the principle of loyalty to the client is not compromised. Second, the rule of disqualification should not be so broadly cast as to preclude other persons from having reasonable choice of legal counsel. Third, the rule of disqualification should not unreasonably hamper lawyers from forming new associations and taking on new clients after having left a previous association. In this connection, it should be recognized that today many lawyers practice in firms, that many to some degree limit their practice to one field or another, and that many move from one association to another several times in their careers. If the concept of imputed disqualification were defined with unqualified rigor, the result would be radical curtailment of the opportunity of lawyers to move from one practice setting to another and of the opportunity of clients to change counsel.
 Reconciliation of these competing principles in the past has been attempted under two rubrics. One approach has been to seek per se rules of disqualification. For example, it has been held that a partner in a law firm is conclusively presumed to have access to all confidences concerning all clients of the firm. Under this analysis, if a lawyer has been a partner in one law firm and then becomes a partner in another law firm, there is a presumption that all confidences known by a partner in the first firm are known to all partners in the second firm. This presumption might properly be applied in some circumstances, especially where the client has been extensively represented, but may be unrealistic where the client was represented only for limited purposes. Furthermore, such a rigid rule exaggerates the difference between a partner and an associate in modern law firms.
 The other rubric formerly used for dealing with vicarious disqualification is the appearance of impropriety proscribed in Canon 9 of the Code of Professional Responsibility. Applying this rubric presents two problems. First, the appearance of impropriety can be taken to include any new client-lawyer relationship that might make a former client feel anxious. If that meaning were adopted, disqualification would become little more than a question of subjective judgment by the former client. Second, since "impropriety" is undefined, the term "appearance of impropriety" is question-begging. It therefore has to be recognized that the problem of imputed disqualification cannot be properly resolved either by simple analogy to a lawyer practicing alone or by the very general concept of appearance of impropriety.
 A rule based on a functional analysis is more appropriate for determining the question of vicarious disqualification. Two functions are involved: preserving confidentiality and avoiding positions adverse to a client.
 Preserving confidentiality is a question of access to information. Access to information, in turn, is essentially a question of fact in particular circumstances, aided by inferences, deductions, or working presumptions that reasonably may be made about the way in which lawyers work together. A lawyer may have general access to files of all clients of a law firm and may regularly participate in discussions of their affairs; it should be inferred that such a lawyer in fact is privy to all information about all the firm’s clients. In contrast, another lawyer may have access to the files of only a limited number of clients and participate in discussion of the affairs of no other clients; in the absence of information to the contrary, it should be inferred that such a lawyer in fact is privy to information about the clients actually served but not those of other clients.
 Application of paragraph (b) depends on a situation’s particular facts. In any such inquiry, the burden of proof should rest upon the firm whose disqualification is sought.
 The provisions of paragraph (b) which refer to possession of protected information operate to disqualify the firm only when the lawyer involved has actual knowledge of information protected by Rule 1.6. Thus, if a lawyer while with one firm acquired no knowledge of information relating to a particular client of the firm, and that lawyer later joined another firm, neither the lawyer individually nor the second firm is disqualified from representing another client in the same or a substantially related matter even though the interests of the two clients conflict.
 Independent of the question of disqualification of a firm, a lawyer changing professional association has a continuing duty to preserve confidentiality of information about a client formerly represented. See Rule 1.6.
 The second aspect of loyalty to a client is the lawyer’s obligation to decline subsequent representations involving positions adverse to a former client arising in substantially related matters. This obligation requires abstention from adverse representations by the individual lawyer involved, and may also entail abstention of other lawyers through imputed disqualification. Hence, this aspect of the problem is governed by the principles of Rule 1.9. Thus, under paragraph (b), if a lawyer left one firm for another, the new affiliation would preclude the lawyer’s new firm from continuing to represent clients with interests materially adverse to those of the lawyer’s former clients in the same or substantially related matters. In this respect paragraph (b) is at odds withand thus must be understood to rejectthe dicta expressed in the "second" hypothetical in the second paragraph of footnote 5 of Brown v. District of Columbia Board of Zoning Adjustment, 486 A.2d 37, 42 n.5 (D.C. 1984) (en banc), premised on LaSalle National Bank v. County of Lake, 703 F.2d 252, 257-59 (7th Cir. 1983).
 The concept of "former client" as used in paragraph (b) extends only to actual representation of the client by the newly affiliated lawyer while that lawyer was employed by the former firm. Thus, not all of the clients of the former firm during the newly affiliated lawyer’s practice there are necessarily deemed former clients of the newly affiliated lawyer. Only those clients with whom the newly affiliated lawyer in fact personally had a lawyer-client relationship are former clients within the terms of paragraph (b).
 Conversely, when a lawyer terminates an association with a firm, paragraph (c) provides that the old firm may not thereafter represent clients whose interests are materially adverse to those of the formerly associated lawyer’s client in respect to a matter that is the same or substantially related to a matter with respect to which the formerly associated lawyer represented the client during the former association. For example, if a lawyer who represented a client in a litigation while with Firm A departs the firm, taking to the lawyer’s new firm the litigation, Firm A may not, despite the departure of the lawyer, who takes the matter and the client to the new firm, undertake a representation adverse to the former client in that same litigation. See Rule 1.9 and the Comment thereto for the definition of "substantially related matter."
 The last sentence of paragraph (b) limits the imputation rule in certain limited circumstances. Those circumstances involve situations in which any secrets or confidences obtained were received before the lawyer had become a member of the Bar, but during a time when such person was providing assistance to another lawyer. The typical situation is that of the part-time or summer law clerk, or so-called summer associate. Other types of assistance to a lawyer, such as working as a paralegal or legal assistant, could also fall within the scope of this sentence. The limitation on the imputation rule is similar to the provision dealing with judicial law clerks under Rule 1.11(b). Not applying the imputation rule reflects a policy choice that imputation in such circumstances could unduly impair the mobility of persons employed in such nonlawyer positions once they become members of the Bar. The personal disqualification of the former nonlawyer is not affected, and the lawyer who previously held the nonlegal job may not be involved in any representation with respect to which the firm would have been disqualified but for the last sentence of paragraph (b). Rule 1.6(g) provides that the former nonlawyer is subject to the requirements of Rule 1.6 (regarding protection of client confidences and secrets) just as if the person had been a member of the Bar when employed in the prior position.
Lawyers Assisting the Office of Corporation Counsel and the District
of Columbia Financial Responsibility and Management Assistance Authority
 The Office of Corporation Counsel and the District of Columbia Financial Responsibility and Management Assistance Authority may experience periods of peak need for legal services which cannot be met by normal hiring programs, or may experience problems in dealing with a large backlog of matters requiring legal services. In such circumstances, the public interest is served by permitting private firms to provide the services of lawyers affiliated with such private firms on a temporary basis to assist the Office of Corporation Counsel and the District of Columbia Financial Responsibility and Management Assistance Authority. Such arrangements do not fit within the classical pattern of situations involving the general imputation rule of paragraph (a). Provided that safeguards are in place which preclude the improper disclosure of client confidences or secrets, and the improper use of one client’s confidences or secrets on behalf of another client, the public interest benefits of such arrangements justify an exception to the general imputation rule, just as comment  excludes from the definition of "firm" lawyers employed by a government agency or other government entity. Lawyers assigned to assist the Office of Corporation Counsel or the District of Columbia Financial Responsibility and Management Assistance Authority pursuant to such temporary programs are, by virtue of paragraph (e), treated as if they were employed as government employees and as if their affiliation with the private firm did not exist during the period of temporary service with the Office of Corporation Counsel or the District of Columbia Financial Responsibility and Management Assistance Authority. See Rule 1.11(h) with respect to the procedures to be followed by lawyers participating in such temporary programs and by the firms with which such lawyers are affiliated after the participating lawyers have ended their participation in such temporary programs.
 The term "made available to assist the Office of Corporation Counsel or the District of Columbia Financial Responsibility and Management Assistance Authority in providing legal services" in paragraph (e) contemplates the temporary cessation of practice with the firm during the period legal services are being made available to the Office of Corporation Counsel or the District of Columbia Financial Responsibility and Management Assistance Authority, so that during that period the lawyer’s activities which involve the practice of law are devoted fully to assisting the Office of Corporation Counsel or the District of Columbia Financial Responsibility and Management Assistance Authority.
 Rule 1.10(e) prohibits a lawyer who is assisting the Office of Corporation Counsel or the District of Columbia Financial Responsibility and Management Assistance Authority from representing that office in any matter in which the lawyer’s firm represents an adversary. Rule 1.10(e) does not, however, by its terms, prohibit lawyers assisting the Office of Corporation Counsel or the District of Columbia Financial Responsibility and Management Assistance Authority from participating in every matter in which the Corporation Counsel or the District of Columbia Financial Responsibility and Management Assistance Authority is taking a position adverse to that of a current client of the firm with which the participating lawyer was affiliated prior to joining the program of assistance to the Office of Corporation Counsel or the District of Columbia Financial Responsibility and Management Assistance Authority. Such an unequivocal prohibition would be overly broad, difficult to administer in practice, and inconsistent with the purposes of Rule 1.10(e).
 The absence of such a per se prohibition in Rule 1.10(e) does not diminish the importance of a thoughtful and restrained approach to defining those matters in which it is appropriate for a participating lawyer to be involved. An appearance of impropriety in programs of this kind can undermine the public’s acceptance of the program and embarrass the Office of Corporation Counsel or the District of Columbia Financial Responsibility and Management Assistance Authority, the participating lawyer, that lawyer’s law firm and clients of that firm. For example, it would not be appropriate for a participant lawyer to engage in a representation adverse to a party who is known to be a major client of the participating lawyer’s firm, even though the subject matter of the representation of the Office of Corporation Counsel or the District of Columbia Financial Responsibility and Management Assistance Authority bears no substantial relationship to any representation of that party by the participating lawyer’s firm. Similarly, it would be inappropriate for a participating lawyer to be involved in a representation adverse to a party that the participating lawyer has been personally involved in representing while at the firm, even if the client is not a major client of the firm. The appropriate test is that of conservative good judgment; if any reasonable doubts concerning the unrestrained vigor of the participating lawyer’s representation on behalf of the Office of Corporation Counsel or the District of Columbia Financial Responsibility and Management Assistance Authority might be created, the lawyer should advise the appropriate officials of the Office of Corporation Counsel or the District of Columbia Financial Responsibility and Management Assistance Authority and decline to participate. Similarly, if participation on behalf of the Office of Corporation Counsel or the District of Columbia Financial Responsibility and Management Assistance Authority might reasonably give rise to a concern on the part of a participating lawyer’s firm or a client of the firm that its secrets or confidences (as defined by Rule 1.6) might be compromised, participation should be declined. It is not anticipated that situations suggesting the appropriateness of a refusal to participate will occur so frequently as to significantly impair the usefulness of the program of participation by lawyers from private firms.
 The primary responsibility for identifying situations in which representation by the participating lawyer might raise reasonable doubts as to the lawyer’s zealous representation on behalf of the Office of Corporation Counsel or the District of Columbia Financial Responsibility and Management Assistance Authority must rest on the participating lawyer, who will generally be privy to nonpublic information bearing on the appropriateness of the lawyer’s participation in a matter on behalf of the Office of Corporation Counsel or the District of Columbia Financial Responsibility and Management Assistance Authority. Recognizing that many representations by law firms are nonpublic matters the existence and nature of which may not be disclosed consistent with Rule 1.6, it is not anticipated that law firms from whom participating lawyers have been drawn would be asked to perform formal "conflicts checks" with respect to matters in which participating lawyers may be involved. However, consultations between participating lawyers and their law firms to identify potential areas of concern, provided that such consultations honor the requirements of Rule 1.6, are appropriate to protect the interests of all involvedthe Office of Corporation Counsel, the District of Columbia Financial Responsibility and Management Assistance Authority, the participating lawyer, that lawyer’s law firm and any clients whose interests are potentially implicated.