Wiretapping for national security : hearings before a subcommittee of the Committee on the Judiciary, United States Senate, Eighty-third Congress, second session on S. 832, to authorize acquisition and interception of communications in interest of national security and defense : S. 2753, to allow admission of certain types of evidence in the federal courts of the United States against defendants prosecuted for treason, espionage, and other crimes involving the national security : S. 3229, to prohibit wiretapping by any person other than a duly authorized law-enforcement officer engaged in the investigation of offenses involving the internal security of the United States and H.R. 8649, to authorize the admission into evidence in certain criminal proceedings of information intercepted in national security investigations, and for other purposes, April 20, 28, 29, May 6 and 12, 1964.