 Eight others implicated in Lincoln 's assassination were tried by a military tribunal in Washington , D.C. , and found guilty on June 30 , 1865 . Mary Surratt , Lewis Powell , David Herold , and George Atzerodt were hanged in the Old Arsenal Penitentiary on July 7 , 1865 . Samuel Mudd , Samuel Arnold , and Michael O 'Laughlen were sentenced to life imprisonment at Fort Jefferson in Florida 's Dry Tortugas ; Edmund Spangler was given a six @-@ year term in prison . O ' Laughlen died in a yellow fever epidemic there in 1867 . The others were eventually pardoned in February 1869 by President Andrew Johnson . 
