In the complex realm of corporate litigation, the sanctity of attorney-client privilege is often the backbone of a robust defense strategy. Yet, the scope of this privilege can blur when multiple corporations collaborate with separate legal teams. In such situations, the common interest privilege (CIP) becomes a crucial tool, enabling corporations with distinct legal counsel to share information and strategize jointly without forfeiting confidentiality. This extension is vital in an era where legal alliances are essential for navigating complex legal disputes. However, an examination across the U.S. Courts of Appeals reveals significant differing requirements to invoke CIP, making it crucial for corporations to understand these nuances to avoid the risk of their intended confidential communications being unexpectedly exposed in discovery.

What Is Common Interest Privilege?

Common interest privilege, also known as the community of interest or joint defense privilege, extends attorney-client privilege to protect communications between separate parties with shared legal interests but different representation. Waller v. Fin. Corp. of Am., 828 F.2d 579, 583 n.7 (9th Cir.1987); United States v. Bay State Ambulance & Hosp. Rental Serv., 874 F.2d 20, 28 (1st Cir. 1989). Originating from the need for codefendants to protect joint defense efforts in criminal cases, CIP has expanded to cover civil litigation, regulatory matters, and multi-party business disputes.