Various methods are used in litigation to limit the disclosure of information and documents to opposing parties. One is to invoke a privilege. The most common privileges are the work product doctrine and the attorney-client privilege.
Some jurisdictions have adopted a principle related to the work product doctrine and the attorney-client privilege. This doctrine is most often known as “common interest” or the “joint defense” doctrine, but other names have been used to describe the concept. Common interest and joint defense have separate origins, the former having its roots in criminal law, whereas the latter first arose in civil litigation. At present the two phrases are often used interchangeably. The former is used in this article.
As its name implies, the common interest doctrine may come into play where two or more parties find it useful to share information that they consider otherwise privileged. It allows the confidential sharing of privileged information. Such sharing generally must occur either through or in the presence of their counsel. The exchange must take place for the purpose of formulating a common strategy, usually among defendants.
Some commentators have suggested that the purpose of the common interest doctrine is to encourage the free flow of information and also to enhance the quality of legal advice. Naturally the beneficiaries are the parties who claim protection under the doctrine, and not the parties seeking the information at issue. For this reason, and because it impedes the free flow of information among all parties, courts often favor a narrow construction of the common interest doctrine.
Some describe the common interest doctrine as a variant or extension of the work product doctrine or the attorney-client privilege, but it is typically utilized to prevent the waiver of those exclusionary rules. In other words, the common interest doctrine provides an exception to the general rule that a party waives either the work product doctrine or the attorney-client privilege by sharing protected information to a third party.
Courts applying the common interest doctrine generally require a showing that (a) the information is protected by an underlying privilege; (b) that the parties shared the information when they also shared a common legal (not merely commercial) interest; (c) they shared the information in order to advance that common interest; and (d) the parties have not otherwise waived the underlying privilege. The burden of proving those elements generally is imposed upon the party invoking the common interest doctrine.
The common interest principle has not been adopted in all jurisdictions, and those that have adopted it do not apply it uniformly. In some states, the interest among the sharing parties must be pristinely identical, whereas others impose a less stringent standard, allowing the use of the doctrine among parties who may have (or later develop) some conflicting adverse interests at the time of the exchange. Some courts require a case to be pending or anticipated at the time of the information sharing, but others do not. Before engaging in an exchange of information with other parties, attorneys must review the laws of the controlling jurisdiction to determine whether the principle has been recognized, and if so, identify its requisite elements. An express agreement among the parties is not required, but in most states it is recommended, given the limited guidance available as to the operation of the doctrine. To ensure the intended protection, at the outset of the litigation (i.e., before sharing any information) participants should consider asking the court to expressly recognize the privilege and preclude discovery into certain matters. Further, communication of confidential information should be limited to matters within the common interests of the participants, and the parties to the common interest should take reasonable steps to maintain the confidentiality of the information.