A defendant waives the defense of lack of personal jurisdiction by appearing in an action, either formally or informally, without raising the defense in an answer or pre-answer motion to dismiss. A defendant may appear informally by actively litigating the action before the court. When a defendant participates in a lawsuit on the merits, he indicates an intention to submit to the court's jurisdiction over the action, and by appearing informally in this manner, the defendant confers in personam jurisdiction on the court. Here, the defendants waived the defense of lack of personal jurisdiction by opposing a prior motion by the plaintiff for leave to enter a default judgment against them on the ground that the plaintiff failed to establish the merits of its cause of action against them and by thereafter opposing another prior motion by the plaintiff and filing a cross-motion for affirmative relief, all without asserting an objection to jurisdiction.
BAC Home Loans Servicing, L.P. v. Davis, NY Slip Op 04859 (2d Dep't September 10, 2025)
Here is the decision.