Under the Speech and Debate Clause of the U.S. Constitution (Art. I, §6), "for any speech or debate in either House," Senators and Representatives "shall not be questioned in any other Place."
An ancient legislative privilege, the Speech and Debate Clause provides lawmakers immunity from most civil and criminal lawsuits relating to their conduct of legislative business. Decisions by the U.S. Supreme Court involving the Speech and Debate Cause indicate that it covers more than debate on the House or Senate floor. The Court's holdings provide Members absolute protection when introducing and voting on bills and resolutions, preparing and submitting committee reports, acting at committee hearings and meetings, and conducting investigations and issuing subpoenas.