Pendent jurisdiction allows a plaintiff who has a jurisdictionally sufficient federal question claim to join to the original complaint and related claims that are otherwise jurisdictionally defective. It is the authority of a federal court to hear a closely related state law claim against a party who is already facing a federal claim.
Such jurisdiction is granted mainly to encourage economy in litigation on one hand and to ensure fairness on the other hand by eliminating the need for a separate federal and state trial hearing essentially the same facts yet potentially reaching opposite conclusions. Generally, it is invoked when a plaintiff brings a federal question claim against a nondiverse defendant and seeks to have a related state law claim against the same defendant adjudicated by the federal court as an incident to the federal claim. Pendent jurisdiction generally views matters from the plaintiff’s perspective.
Two conditions to invoke pendent jurisdiction of federal courts are: i) there must be a federal claim and ii ) the non-federal claim in the case should arise from a common nucleus of operative fact such that a plaintiff would ordinarily be expected to try them in one judicial proceeding.