Practice point: There are three conditions that a plaintiff must satisfy before claims against one defendant may relate back to claims asserted against another: (1) both claims must arise out of the same conduct, transaction, or occurrence; (2) the new party must be united in interest with the original defendant, and by reason of that relationship can be charged with such notice of the institution of the action that he or she will not be prejudiced in maintaining a defense on the merits; and (3) the new party either knew or should have known that, but for a mistake by the plaintiff as to the identity of the proper parties, the action would have been brought against that party as well.
Student note: To establish the requisite unity of interest, the plaintiff had to show that their interest in the subject matter of the action is such that the defendants stand or fall together, and that a judgment against one would similarly affect the other. If the relationship between the defendants is such that one may have a defense not available to the other, they are not united in interest. In addition, interests are united only where one defendant is vicariously liable for the acts of the other.
Case: Berkeley v. 89th Jamaica Realty Co., L.P., NY Slip Op 02640 (2d Dep't 2016)
Here is the decision.
Tomorrow's issue: Sanctions for destruction of evidence.