A tortious interference with contract claim is only proper when a defendant causes a third-party (not the plaintiff) to breach the underlying contract. Here's a dose of some cold, hard truth: As a practical matter it is far from simple to prove a tortious interference with contract claim under New York law.Under New York law, a tort action for interference with a contractual relationship must be based upon five essential elements. Our New York City business litigation lawyers handle tortious interference with business cases for business of varying disciplines and sizes. According to law, when a tort is committed, the victim has the option to file a lawsuit against the alleged perpetrator. Long Island, New York business litigation and breach of contract lawyer Jonathan Cooper discusses how to prove a tortious interference claim under NY law. Long Island, New York business litigation and breach of contract lawyer Jonathan Cooper discusses how to prove a tortious interference claim under NY law. What this means is that they must have known about the contractual relationship and caused the breach anyway. A defendant may be justified or privileged to interfere with contractual or business relationships in certain circumstances. Proving to a court that a third party intentionally interfered in a business relationship or contract is complicated.