Under the relation back doctrine, the addition of a new defendant requires the following: (1) both claims arise out of same conduct, transaction, or event; (2) the new party is 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 will not be prejudiced in defending on the merits; and (3) the new party knew or should have known that, but for an excusable mistake by plaintiff as to the identity of the proper parties, the action would have been brought against him as well.
Stanger v. Shoprite of Monroe, NY, NY Slip 00820 (1st Dep't February 4, 2020)
Here is the decision.
