In Washington's Old Penitentiary, the taking of evidence in the Lincoln conspiracy trial begins
The nine officers of the Commission to try the accused plotters - seven generals and two colonels - had been named on May 6, 1865. Preliminaries complete, the taking of testimony began in earnest in the hearing room at the Old Washington Penitentiary in the grounds of the Washington Arsenal and continued until June 14, 1865. After final arguments, deliberation began June 29, 1865, and sentences pronounced on July 6, 1865. (By John Osborne)
Clara E. Laughlin, The Death of Lincoln: The Story of Booth's Plot, His Deed and the Penalty (New York: Doubleday, Page and Company, 1909), 190-191.