He found his way through the formerly unobtainable files of J. Edgar Hoover, whom he called “an insubordinate bureaucrat in charge of a lawless organization.”
Athan Theoharis, a pre-eminent historian of the F.B.I. whose indefatigable research into the agency’s formerly unobtainable files produced revelations about decades of civil liberties abuses under the leadership of J. Edgar Hoover, died on July 3 at his home in Syracuse, N.Y. He was 84.
Beginning in the mid-1970s, Professor Theoharis, who taught history at Marquette University in Milwaukee, deftly used Freedom of Information Act requests to pry open the F.B.I.’s deep well of secrets, including the extent to which Hoover compiled damning information on public officials and his cooperation with Senator Joseph McCarthy’s campaign against people he accused of being Communists.
The documents showed the extent of the agency’s break-ins and its illegal surveillance of left-wing organizations; its pursuit of allegations that President Dwight D. Eisenhower had extramarital affairs; and the use of the F.B.I. by presidents of both parties for political purposes.