You would use existing case law to attempt to prove the existence or nonexistent of contractual intent. Some major cases that a person could draw supporting evidence are: Lumbreras v Rocha 2012 Tex. App. LEXIS 97 (13th Dist. 2012) All Star Championship Racing, Inc. v. O'reilly Automotive Stores, Inc. 2012 U.S. Dist. LEXIS 34951 (C.D. Ill. 2012)