(a) A lawyer who has formerly represented a client in a matter shall not thereafter represent another person in the same or a substantially related matter in which that person’s interests are materially adverse to the interests of the former client unless the former client gives informed consent, confirmed in writing.
(b) Unless the former client gives informed consent, confirmed in writing, a lawyer shall not knowingly represent a person in the same or a substantially related matter in which a firm with which the lawyer formerly was associated had previously represented a client:
(1) whose interests are materially adverse to that person; and
(2) about whom the lawyer had acquired information protected by RPCs 1.6 and 1.9(c) that is material to the matter.
(c) A lawyer who has formerly represented a client in a matter or whose present or former firm has formerly represented a client in a matter shall not thereafter reveal information relating to the representation or use such information to the disadvantage of the former client unless (1) the former client gives informed consent, confirmed in writing, or (2) these Rules would permit or require the lawyer to do so with respect to a client, or (3) the information has become generally known.
 After termination of a client-lawyer relationship, a lawyer has certain continuing duties with respect to confidentiality and conflicts of interest and thus may not represent another client except in conformity with this Rule. Current and former government lawyers must comply with this Rule only to the extent required by RPC 1.11.
Changing Sides in a Matter
[1a] Representing one side in a lawsuit and then switching to represent the other in the same matter clearly implicates loyalty to the first client and protection of that client’s confidences. Similar considerations apply in non-litigation matters. Thus, a lawyer negotiating a complex agreement on behalf of a seller could not withdraw and represent the buyer against the interests of the seller in the same transaction. Nor could a lawyer who has represented multiple clients in a matter ordinarily represent one of the clients against the others in the same matter after a dispute arose among the clients in that matter, unless all affected clients give informed consent. See Comment .
 The scope of a “matter” for purposes of this Rule depends on the facts of a particular situation or transaction. The appropriateness of the subsequent representation will depend on the scope of the representation in the former matter, the scope of the proposed representation in the current matter, and its relationship to the former matter. The lawyer’s involvement in a matter can also be a question of degree. When a lawyer has been directly involved in a specific transaction, subsequent representation of other clients with materially adverse interests in that transaction clearly is prohibited. On the other hand, a lawyer who recurrently handled a type of problem for a former client is not precluded from later representing another client in a factually distinct problem of that type, even though the subsequent representation involves a position adverse to the prior client. Similar considerations can apply to the reassignment of military lawyers between defense and prosecution functions within the same military jurisdictions. The underlying question is whether the lawyer was so involved in the matter that the subsequent representation can be justly regarded as a changing of sides in the matter in question.
Substantially Related Matters
 Matters are “substantially related” for purposes of this Rule if they involve the same transaction or legal dispute or other work the lawyer performed for the former client or if there is a substantial risk that confidential factual information that would normally have been obtained in the prior representation would materially advance the client’s position in the subsequent matter, unless that information has become generally known. Any conclusion or presumption concerning the type of confidential factual information that would normally have been obtained in the prior representation may be overcome or rebutted by the lawyer by proof concerning the information actually received in the prior representation.
Loyalty to Former Client
[3a] Matters are substantially related if they involve the same transaction or legal dispute or other work the lawyer performed for the former client. For example, a lawyer may not on behalf of a later client attack the validity of a document that the lawyer drafted if doing so would materially and adversely affect the former client. Similarly, a lawyer may not represent a debtor in bankruptcy in seeking to set aside a security interest of a creditor that is embodied in a document that the lawyer previously drafted for the creditor. Although the subsequent representation is a different matter, it is substantially related to the former matter because it involves work done for the former client. The lawyer’s duty of loyalty survives the termination of the former representation to the extent that it precludes the lawyer from acting to deprive the former client of the benefit of the lawyer’s prior work on the former client’s behalf.
[3b] Even where the current matter does not involve the work previously done by the lawyer for the former client, it may still be substantially related to the former matter if there is a substantial risk that confidential factual information that would normally be obtained in the prior representation would materially advance the client’s position in the subsequent matter. For example, a lawyer who has represented a businessperson and learned extensive private financial information about that person may not then ordinarily represent that person’s spouse in seeking a divorce. Similarly, a lawyer who has previously represented a client in securing environmental permits to build a shopping center would be precluded from representing neighbors seeking to oppose rezoning of the property on the basis of environmental considerations; however, the lawyer would not be precluded, on the grounds of substantial relationship, from defending a tenant of the completed shopping center in resisting eviction for nonpayment of rent.
[3c] Formerly confidential information that has been disclosed to the public or to other parties adverse to the former client ordinarily will not be disqualifying. Information acquired in a prior representation may have been rendered obsolete by the passage of time, a circumstance that may be relevant in determining whether two representations are substantially related. Information that might be confidential for some purposes under these Rules (so that, for example, a lawyer would not be free to discuss it publicly) might nonetheless be so general, readily observable, or of so little value in the subsequent litigation that it should not by itself result in a substantial relationship being found. Thus, a lawyer may master a particular substantive area of the law while representing a client, but that does not preclude the lawyer from later representing another client adversely to the first in a matter involving the same legal issues, if the facts are not substantially related. In the case of an organizational client, general knowledge of the client’s policies and practices ordinarily will not preclude a subsequent representation; on the other hand, knowledge of specific facts gained in a prior representation that are relevant to the matter in question ordinarily will preclude such a representation. For example, a lawyer might also have learned a former client’s preferred approach to bargaining in settlement discussions or negotiating business points in a transaction, willingness or unwillingness to be deposed by an adversary, or financial ability to withstand extended litigation or contract negotiations. Only when such information will be directly in issue or of unusual value in the subsequent matter will it be independently relevant in assessing a substantial relationship.
[3d] Inquiries concerning the existence, exchange, and potential for use of such confidential information may themselves raise concerns and difficulties. A concern to protect a former client’s confidential information would be self-defeating if, in order to obtain its protection, the former client were required to reveal in a public proceeding the particular communication or other confidential information that could be used in the subsequent representation. On the other hand, closed or in camera proceedings may implicate issues of fairness to other parties. Further, the interests of subsequent clients also militate against extensive inquiry into the precise nature of the lawyer’s representation of the subsequent client and the nature of exchanges between them.
[3e] The substantial relationship test attempts to avoid requiring actual disclosure of confidential information by focusing upon the general features of the matters involved and inferences as to the likelihood that confidences were imparted by the former client that could be used to adverse effect in the subsequent representation. Thus, a former client is not required to reveal the confidential information learned by the lawyer in order to establish a substantial risk that the lawyer has confidential information to use in the subsequent matter. In the first instance, a preliminary conclusion about the possession of such information may be based on the nature of the services the lawyer provided the former client and information that would in ordinary practice be learned by a lawyer providing such services. Consistent with the preservation of the former client’s confidentiality, however, the inquiry into the issues involved in the prior representation should be as specific as possible, so as to avoid undue impairment of the subsequent client’s interest in selection of counsel of choice and the capacity of the lawyer, within appropriate limits, to defeat any presumption or inference concerning the lawyer’s receipt or exchange of confidential information.
Lawyers Moving Between Firms
 When lawyers have been associated within a firm but then end their association, the question of whether a lawyer should undertake representation is more complicated. There are several competing considerations. First, the client previously represented by the former firm must be reasonably assured that the principle of loyalty to the client is not compromised. Second, the rule should not be so broadly cast as to preclude other persons from having reasonable choice of legal counsel. Third, the rule 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 lawyers 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 imputation were applied 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.
 Paragraph (b) operates to disqualify the lawyer only when the lawyer involved has actual knowledge of information protected by RPCs 1.6 and 1.9(c). Thus, if a lawyer while with one firm acquired no knowledge or 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 related matter even though the interests of the two clients conflict. See RPC 1.10(b) for the restrictions on a firm once a lawyer has terminated association with the firm.
 Application of paragraph (b) depends on a situation’s particular facts, 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 discussions 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. In such an inquiry, the burden of proof should rest upon the firm whose disqualification is sought.
 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 RPCs 1.6 and 1.9(c).
 Paragraph (c) provides that information acquired by the lawyer in the course of representing a client may not subsequently be revealed by the lawyer or used by the lawyer to the disadvantage of the client. However, the fact that a lawyer has once served a client does not preclude the lawyer from using or disclosing generally known information about that client when later representing another client.
[8a] Whether information is generally known depends on all circumstances relevant in obtaining the information. Information contained in books or records in public libraries, public-record depositaries, such as government offices, or in publicly accessible electronic-data storage is generally known if the particular information is obtainable through publicly available indexes and similar methods of access. Information is not generally known when a person interested in knowing the information could obtain it only by means of special knowledge or substantial difficulty or expense. Special knowledge includes information about the whereabouts or identity of a person or other source from which the information can be acquired, if those facts are not themselves generally known. A lawyer may not, however, justify adverse use or disclosure of client information simply because the information has become known to third persons, if it is not otherwise generally known. Even if permitted to disclose information relating to a former client’s representation, a lawyer should not do so unnecessarily.
 The provisions of this Rule are for the protection of former clients and can be waived if the client gives informed consent, which consent must be confirmed in writing under paragraphs (a) and (b). See RPC 1.0(e). With regard to the effectiveness of an advance waiver, see Comment  to RPC 1.7. With regard to disqualification of a firm with which a lawyer is or was formerly associated, see RPC 1.10.
Relation to Other Rules
 Except in situations governed by RPCs 1.11 and 6.5(a), RPC 1.9 applies in all circumstances in which a lawyer has previously represented a client as an advocate, an advisor, an intermediary, or an author of a legal opinion to be rendered on behalf of a client for use by a third person. Except as provided in RPC 2.4, RPC 1.9 does not apply to parties being served by a lawyer as a dispute resolution neutral. If, however, the lawyer’s service as a neutral will be materially adverse to a former client and the dispute is substantially related to the former representation, the lawyer must afford the former client the protections of RPC 1.9.
“Confirmed in writing” See RPC 1.0(b)
“Firm” See RPC 1.0(c)
“Informed consent” See RPC 1.0(e)
“Knowingly” and known” See RPC 1.0(f)
“Material” and “materially” See RPC 1.0(o)
“Substantially” See RPC 1.0(l)