What happened in New York Times Co. v. Sullivan?

In this 1964 case, The New York Times printed an editorial advertisement submitted by the Committee to Defend Dr. Martin Luther King Jr. The advertisement spoke about civil rights abuses in the state of Alabama, specifically in the city of Montgomery, Alabama. Some of the statements in the advertisement were false and the commissioner in charge of the police in Montgomery, a Mr. L.B. Sullivan, sued for defamation. He prevailed before the Alabama state courts, but the U.S. Supreme Court reversed. The court decided:

Thus we consider this case against the background of a profound national commitment to the principle that debate on public issues should be uninhibited, robust, and wide open, and that it may well include vehement, caustic, and sometimes unpleasantly sharp attacks on government and public officials … erroneous statement is inevitable in free debate, and that it must be protected if the freedoms of expression are to have the breathing space that they need … to survive….

The interest of the public here outweighs the interest of appellant or any other individual. The protection of the public requires not merely discussion, but information. Political conduct and views which some respectable people approve, and others condemn, are constantly imputed to Congressmen. Errors of fact, particularly in regard to a man’s mental states and processes, are inevitable…. Whatever is added to the field of libel is taken from the field of free debate….

The constitutional guarantees require, we think, a federal rule that prohibits a public official from recovering damages for a defamatory falsehood relating to his official conduct unless he proves that the statement was made with actual malice that is, with knowledge that it was false or with reckless disregard of whether it was false or not….

We hold today that the Constitution delimits a State’s power to award damages for libel in actions brought by public officials against critics of their official conduct. Since this is such an action, the rule requiring proof of actual malice is applicable.