Can I sue for defamatory statements made by a witness under oath in court?
Statements in a judicial proceeding are privileged. A judge, juror, lawyers, witnesses, or other parties are absolutely protected from defamation actions. For example, you are involved in an employment dispute with your former employer. The employer testifies that you are a drunk and a thief, while knowing the statements are untrue. Though untrue, your former employer can make the defamatory statements on the stand without being sued by you afterwards. Witnesses who lie are instead subject to perjury charges, a criminal offense that is brought by a district attorney, not a civil claim subject to monetary damages.
Some aspects of the political process are also protected from defamation suits. Federal or state legislators cannot be sued for libel or slander for their statements in committee hearings or during floor debates.