At common law, a defendant is liable to pay damages in tort for actions intended to interfere with the plaintiff's contractual relations with a third party.
In an intentional interference claim, the burden is on the plaintiff to prove the elements of the claim rather than on the defendant to prove that its acts were justified. To prevail on the claim, plaintiff must prove four elements: (1) that a valid contract existed, (2) that defendant had knowledge of the contract, (3) that defendant acted intentionally and improperly, and (4) that plaintiff was injured by the defendant’s actions. United Truck Leasing Corp. v. Geltman, 406 Mass. 811, 812, 551 N.E.2d 20 n. 6 (Mass. 1990).
See also tortious interference.