Many parties to pending or potential litigation likely have been admonished to always copy their lawyer or risk disclosure of communications that could otherwise be subject to attorney-client privilege. Although such advice remains prudent, a recent decision from the Commercial Division of the Supreme Court, New York County highlights the potential importance of—and protection offered by—the sometimes overlooked sibling of attorney-client privilege: the common interest doctrine.

It is hornbook New York law that the attorney-client privilege protects confidential communications between a lawyer and client made for the purpose of seeking and receiving legal advice. See West 87 v. Paul Hastings, 192 N.Y.S.3d 921 (Table), 2023 N.Y. Slip Op. 50821(U), at *2 (Sup. Ct., N.Y Cnty. Aug. 4, 2023); United States v. Adlman, 68 F.3d 1495, 1499 (2d Cir. 1995). The privilege encourages clients to make full and frank disclosures to their attorneys to better enable effective advice and representation. Spectrum Systems International v. Chemical Bank, 78 N.Y.2d 371, 377 (1991); People v. Edney, 39 N.Y.2d 620, 626 (1976). For the privilege to apply, the communications must be between a client and its lawyer and must stay confidential; subsequent disclosure to third parties means those communications generally lose any such protection. See Spectrum, 78 N.Y.2d at 378; Ambac Assurance v. Countrywide Home Loans, 27 N.Y.3d 616, 624 (2016).

In specific circumstances, however, the protections of attorney-client privilege may extend to third parties. The common interest doctrine operates as an "exception to the 'traditional rule that the presence of a third party, not an agent or employee of counsel, at a communication between counsel and client is sufficient to deprive the communication of the confidentiality which is one of the pillars of the privilege.'" Yemini v. Goldberg, 12 Misc. 3d 1141, 1143 (Sup. Ct., Nassau Cnty. 2006) (citation omitted). Pursuant to the common interest doctrine, attorney-client communications disclosed to a third-party may remain privileged if they are shared with parties who have a common legal interest in pending or anticipated litigation. See Ambac, 27 N.Y.3d at 620.