When a congressional committee conducts an investigation, the due process clause requires that it must clearly articulate the subject matter of the investigation and that all questions must be pertinent to the investigation.
During the early years of the Cold War, the House Un-American Activities Committee asked broad-ranging questions of people suspected of having supported communist causes. John Watkins, a former labor leader, agreed to answer questions about his own relationship to the Communist
By a 6-1 vote, the Supreme Court reversed the conviction. Speaking for the Court, Chief Justice Earl Warren
Barenblatt v. United States
Congressional power of investigation
Contempt power of Congress
Due process, procedural