Mcgrain v. Daugherty 273 U.S. 135 (1927)
MCGRAIN v. DAUGHERTY 273 U.S. 135 (1927)
in kilbourn v. thompson (1881) the Supreme Court had held that because Article I of the Constitution assigned Congress no power beyond the lawmaking power, Congress might constitutionally investigate "the private affairs of individuals" only for the purpose of gathering information to write new legislation. McGrain restated this requirement of legislative purpose, but rejected, 8–0, a challenge to the contempt conviction of the brother of Harry M. Daugherty who had failed to appear before a Senate committee investigating the failure of former Attorney General Daugherty to prosecute the malefactors in the Teapot Dome scandal.
In reality the investigation was not aimed at developing new legislation but at exposing malfeasance in the executive branch, a task that might have been deemed constitutionally appropriate for Congress if it were not for the simplistic Kilbourn theory. The gap between theory and reality was bridged by the creation of a presumption that congressional investigations had a legislative purpose, a presumption that was not to be overcome simply by showing that an investigation also had a purpose of public exposure.
theMcGrain technique of requiring a legislative purpose for a congressional investigation, and then invoking a presumption of legislative purpose even when exposure was clearly a principal motive, had important consequences in post-World War II cases where anticommunist investigating committees were seeking to punish leftist speakers by public exposure precisely because the first amendment prohibited Congress from passing legislation punishing such speech. The Court invoked the presumption of legislative purpose both to blind itself to the actual "exposure for exposure's sake" being conducted and to establish a congressional interest in lawmaking that outweighed whatever incidental infringement on speech the Court was willing to see.
(see also: Legislative Investigation.)