Here’s a dog bites man story: the joint defense privilege exists in Massachusetts. For those of you who are unfamiliar with the topic, the joint defense privilege allows parties on the same side of the dispute in a multiparty litigation to share information amongst themselves and their various attorneys without waiving the attorney client privilege. Normally, the privilege only attaches to information kept in confidence by a party and its attorney, and if they disclose it to anyone else, the privilege is lost (or waived, as the litigators say). However, the joint defense privilege allows parties who have a shared interest in litigating against yet another party to disclose information to each other without waiving the privilege. The Massachusetts Supreme Judicial Court has now officially recognized this principle, but what makes it a little bit of a dog bites man story is that Massachusetts lawyers and trial court judges have been acting for decades as though the joint defense privilege exists. The Supreme Judicial Court acknowledged this in its opinion, stating: 

Although this court has not had occasion to consider the common interest doctrine or any of its components, there is no doubt that attorneys and their clients have relied on its implicit existence. It is evident from cases such as Commonwealth v. Beneficial Fin. Co., 360 Mass. 188 (1971), the longest criminal trial in the history of the Commonwealth, that joint defense arrangements have been used in criminal trials in Massachusetts for a substantial period of time. Indeed, in The Society of Jesus of New England v. Commonwealth, 441 Mass. 662, 666 (2004), we noted without comment that the defendants in that criminal case had entered into a "Joint Defense Agreement." The principle, at least in the litigation context, is incorporated into Proposed Mass. R. Evid. 502 (b) (3). The parties have brought to our attention numerous well-reasoned decisions of judges in the Superior Court recognizing the validity of the joint defense privilege in civil cases.

It is not surprising, by the way, that the issue came up, and was finally decided by the Supreme Judicial Court, in an insurance related case; insurance disputes routinely involve multiple parties, from primary carriers to excess carriers to insurance agents to third party administrators, and on and on. It is very difficult for all of the parties on one side or the other of the case to align their positions and litigate effectively without sharing privileged information.