The common interest doctrine can allow separately represented clients to share privileged communications without triggering a waiver. However, the participants usually will not know whether a court will find the doctrine applicable until after they have shared the communications — by which time it is too late.
In Pulse Engineering, Inc. v. Mascon Inc., Civ. No. 08cv595 JM (AJB), 2009 U.S. Dist. LEXIS 92971, at *11 (S.D. Cal. Oct. 1, 2009), the court held that the manufacturer and the seller of an allegedly infringing product shared a legitimate common interest — so their “joint analysis of the accused device” deserved privilege protection. However, less than two weeks later another court held that Whirlpool and its advertising agency did not share a common interest — bluntly warning that adoption of Whirlpool’s common interest argument “would permit two companies to argue a common legal interest simply because they routinely deal with one another and neither desires to be sued.” L.G. Elecs. U.S.A., Inc. v. Whirlpool Corp., No. 08 C 242, 2009 U.S. Dist. LEXIS 95251, at *25 (N.D. Ill. Oct. 13, 2009).
Although the common interest doctrine can be a useful tool in some situations, it can also tempt clients and their lawyers to disclose privileged communications, thinking — erroneously, in some cases — that they are not waiving the privilege.