 After the assassination of President Abraham Lincoln in 1865, Burnett was called upon by Secretary of War Edwin Stanton to be an Assistant Judge Advocate General.Along with him were John Bingham and Joseph Holt, the Judge Advocate General.The accused conspirators where George Atzerodt, David Herold, Lewis Powell, Samuel Arnold, Michael O'Laughlen, Edman Spangler, Samuel Mudd and Mary Surratt.