In the case of St. Amant v. Thompson, 1967, the U.S Supreme Court ruled in favor of a Louisiana politician who was sued for defamation by a deputy sheriff. The court held that false statements about public officials could only be considered defamatory if made with "actual malice" - knowing they were false or showing reckless disregard for their truth or falsity. This ruling expanded on previous decisions regarding libel and slander laws to protect freedom of speech under the First Amendment, even when such speech contains inaccuracies. In this specific case, it was determined that although St.Amant's televised allegations against Thompson may have been incorrect and damaging to his reputation as a law enforcement officer, there wasn't sufficient evidence to prove he had knowingly lied or acted with reckless disregard towards verifying his claims before making them public.

In the dissenting opinion for St. Amant v. Thompson, Justice John Marshall Harlan II argued that the majority's decision to require public officials to prove actual malice in defamation cases was too stringent and could potentially stifle free speech. He contended that this standard would force individuals to self-censor out of fear of litigation, even when they believed their statements were true but lacked irrefutable proof. Furthermore, he criticized the court's reliance on a "reckless disregard" standard as being overly vague and subjective, making it difficult for courts and juries to apply consistently across different cases. Instead, Justice Harlan proposed a negligence-based standard where defendants could be held liable if they failed to exercise reasonable care in verifying their statements' truthfulness before publication.