A tortious interference with contract claim is only proper when a defendant causes a third-party (not the plaintiff) to breach the underlying contract. Our New York City business litigation lawyers handle tortious interference with business cases for business of varying disciplines and sizes.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. Carvel is a case about tortious interference with prospective economic relations, not interference with contract. Cheryl Keeling sued the property manager of her condominium and a real estate broker for defamation and tortious interference with economic advantage. As implied, this type of interference requires a formal business agreement or contract already be in place and then be interfered with.