What is the broad category of defenses available to the tort of defamation? Under what circumstances can the U.S. Constitution be used as a defense to an action for an intentional tort?

Privilege is the broad category of defenses to the tort of defamation. Privilege includes absolute privilege, conditional privilege, and constitutional privilege. Absolute privilege protects the defendant regardless of motive or intent and includes statements made by participants in a judicial proceeding, statements made by members of Congress on the floor of Congress, statements made by certain executive branch officers while performing their governmental duties, and statements regarding a third party made between spouses when they are alone. Qualified or conditional privilege exists to protect the publisher's own legitimate interests, or in some cases, the interests of another. It is forfeited by a publisher who acts in an excessive manner, without probable cause, or for an improper purpose. Constitutional privilege extends to defamatory and false statements about public officials or public figures so long as it is done without malice. In a defamation suit brought by a private person, the plaintiff must prove that the defendant published the defamatory and false comment with malice or negligence.