“Non est factum” is a Latin legal term that means “it is not my deed” or “it is not the act of the person signing.” It is a defense that can be raised in contract law to argue that a person should not be bound by a contract they have signed because they did not understand it or were deceived about its nature or terms. This defense may be used in situations where a person was forced to sign a contract under duress, was a victim of fraud, or where they were not mentally competent to understand the contract’s implications. The assertion of “non est factum” essentially claims that the person signing the contract made a mistake about what they were signing and should not be held responsible for its terms.