Conflicts of Interest
Concurrent versus former clients
Rule 1.7(a) defines a concurrent conflict two ways: representation of one client will be directly adverse to another client, or there is a significant risk the representation will be materially limited by responsibilities to another client, a former client, a third person, or a personal interest. A concurrent conflict is curable by informed consent, confirmed in writing, if the lawyer reasonably believes she can provide competent and diligent representation, the representation is not prohibited by law, the clients are not asserting claims against each other in the same litigation, and no client is represented by another lawyer in the matter as a result.
Rule 1.9 governs former clients: no representation in the same or a substantially related matter in which the new client's interests are materially adverse to the former client without that client's informed written consent, and no use of the former client's confidences to her disadvantage.
Imputation
Rule 1.10 imputes a lawyer's disqualification to the entire firm, but screening with written notice may cure a lateral hire's former-client conflict where the lawyer was not substantially involved. Government lawyers (1.11) and judges, arbitrators, and mediators (1.12) are screened rather than imputed.
Rule 1.8 highlights
Business transactions with a client require terms fair and fully disclosed in writing, informed written consent, and a reasonable chance to seek independent counsel; no gifts procured by undue influence and no drafting an instrument giving the lawyer a gift; third-party payers and aggregate settlements require consent; malpractice liability may be limited only with independent counsel for the client.
Traps
Oral consent is not enough; dropping a client mid-matter to convert a concurrent conflict into a former-client conflict ("hot potato") fails; screening does not cure every conflict.
Worked example
Two long-standing corporate clients ask the firm to litigate against each other. Consent in writing from both is necessary, and unavailable if consent would be unreasonable.