Undue influence

In contract law, a defense that can be used by a party to argue against the formation of a binding contract between two parties. The use of undue influence by one party over another puts the free will of one of the parties entering the contract into question, and therefore leads to the contract being unenforceable and voidable by the victim party. To prove undue influence, a party must show that one party to the contract is a person with weaknesses which make him likely to be affected by such persuasion, and that the party exercising the persuasion is someone in a special relationship with the victim that makes the victim especially susceptible to such persuasion.