McGrain v. Daugherty, 273 U.S. 135; 47 S. Ct. 319; 71 L. Ed. 580 (1927)
Facts—The Senate decided to investigate the activities of Harry M. Daugherty, former attorney general of the United States. It subpoenaed Mally S. Daugherty, a brother of the former attorney general, to appear before the committee that was conducting the hearings. He refused, the Senate issued a warrant to compel him to appear and testify, and the Senate sent McGrain, its deputy sergeant-at-arms, to arrest him. Daugherty applied for and received a writ of habeas corpus to discharge him from custody on the ground that the Senate exceeded its powers under the Constitution.
Question—May Congress compel a private individual to appear before it or one of its committees and give testimony?
Decision—Yes.
Reasons—J. Van Devanter (8–0). The power to legislate carries with it by necessary implication information needed in the rightful exercise of that power and to employ compulsory process for that purpose. Although it was investigating the former attorney general, and the resolution that brought the committee into existence had not in turn avowed its intent to aid legislation, the subject was such that the information received could be of valuable help in enacting further laws.