From the 1930s through the 1950s, Congress intensively investigated perceived political radicals. The House Committee on Un-American Activities focused on suspected communists in the film industry, universities, and labor organizations. Some witnesses refused to testify, pleading the Fifth Amendment—the right not to incriminate oneself. In 1954 labor organizer John Thomas Watkins directly challenged a subcommittee’s right to demand information not pertinent to the investigation. Watkins was convicted of contempt of Congress, but in 1957 the United States Supreme Court decided in his favor, limiting Congress’s investigative powers.
The Bill of Rights is applicable to congressional investigations, as it is to all forms of governmental action
Chief Justice Earl Warren, Watkins v. United States, 1957