The following note on administrative history is provided as a link within this title's description.
Some testimony and information relating to the assassination of President Abraham Lincoln and the attempted assassination of Secretary of State William H. Seward were collected by various officials almost immediately after the crimes were committed on the night of April 14, 1865. In addition to the regular police force of the city of Washington, Secretary of War Edwin M. Stanton called upon the military police attached to the Provost Marshal General's Bureau, retainers of the U.S. Secret Service, corps of detectives and judge advocates attached to the Bureau of Military Justice, Army officers and enlisted men stationed at various points in Washington and surrounding camps and fortifications, and others to aid in the capture of the assassins and their colleagues. After the initial shock of these crimes was over and rewards for the capture of the assassins had been posted, many of these forces were intent upon the capture of the fugitives. The Bureau of Military Justice, however, was steadily at work gathering witnesses and accumulating testimony. And on April 22, 1865, Brevet Colonel Henry L. Burnett, Judge Advocate of the Northern Department with headquarters at Cincinnati, Ohio, was ordered to report to Judge Advocate General of the Army Joseph Holt, Chief of the Bureau of Military Justice, and was, by War Department Special Order No. 180, "specially assigned for duty in the investigation of the murder of President Lincoln, and the attempted assassination of Mr. Seward."
Colonel Burnett was assigned office space in the War Department, and with the assistance of Colonel H.S. Olcutt, Colonel H.H. Wells, and one or two others, immediately began to accumulate all available information and evidence. On May 1, President Andrew Johnson instructed the Assistant Adjutant General to select nine Army officers who were to constitute the Military Commission to try the accused. He also instructed the Judge Advocate General to prefer charges against them and to conduct the trial with the aid of such Assistant or Special Judge Advocates as he might designate. Accordingly a Military Commission was appointed on May 6, 1865, and when it met on May 9, the Judge Advocate General announced that he had appointed the Honorable John A. Bingham and Colonel Burnett as Assistant or Special Judge Advocate.