Final answer:
In libel law, an affirmative defense where the defendant justifies the defamation is truth. The standard of 'actual malice' established by New York Times Co. v. Sullivan requires proof that a false statement was made knowingly or with reckless disregard for the truth, specifically for public officials. Private individuals have different standards as dictated by state law, following the Gertz v. Robert Welch, Inc. case.
Step-by-step explanation:
In libel law, an affirmative defense in which the defendant asserts a justification for having defamed the plaintiff is known as truth as a defense. The landmark case New York Times Co. v. Sullivan established the standard that public officials must prove actual malice to succeed in a defamation case.
To prove actual malice, the plaintiff must show that the statement was made with knowledge of its falsity or with reckless disregard for whether it was true or false. In cases involving private individuals, states have the flexibility to determine their own standards for libel against private individuals as long as they don't impose liability without fault. Gertz v. Robert Welch, Inc. clarified that state standards could not be lower than actual malice and that only actual damages could be awarded if the standard is less stringent.