Reply #83: Congressional investigations... [View All]

"Periodically, the Supreme Court has helped to define the scope and limitations of Congress's power to investigate. In McGrain v. Daugherty (1927) the Court ruled that anyone, even private citizens, could be subpoenaed (compelled) to testify before a congressional committee. And in Sinclair v. United States (1929) the Court said that Congress had the power to investigate anything related to legislation or oversight, the monitoring of the activities of executive agencies. But in Watkins v. United States (1957)—which involved a witness who declined to give names of suspected communists to HUAC—the Court ruled that Congress's investigative powers are limited by the Bill of Rights and that witnesses do not lose those rights when they testify."

http://www.answers.com/topic/congressional-investigations