Still, for conspirators such as Lewis Powell and David Herold, there was no question of their guilt -- Powell had attacked Secretary of State William Seward, and Herold was with him. Later Herold was captured at the same time that John Wilkes Booth was shot dead. George Atzerodt was likewise clearly guilty of conspiring to kill Vice President Johnson, though he chickened out when it came time to try.
But what about Mary Surratt, owner of the boarding house where the plot was hatched? It seems likely that she knew what was going on, and perhaps even helped, but the evidence isn't absolutely conclusive. A shadow of a doubt might have saved her in a civilian court, but the military commission thought she was guilty.
"On June 29, 1865, the Military Commission met in secret session to begin its review of the evidence in the seven-week long trial," wrote Douglas Linder in Famous American Trials. "A guilty verdict could come with a majority vote of the nine-member commission; death sentences required the votes of six members. The next day, it reached its verdicts. The Commission found each of the prisoners guilty of at least one of the conspiracy charges. Four of the prisoners (Mary Surratt, Lewis Powell, George Atzerodt, and David Herold) were sentenced 'to be hanged by the neck until he [or she] be dead.' Samuel Arnold, Dr. Samuel Mudd and Michael O'Laughlen were sentenced to 'hard labor for life, at such place at the President shall direct.' Edman Spangler received a six-year sentence.
"The Commission forwarded its sentences and the trial record to President Johnson for his review. Five of the nine Commission members, in the transmitted record, recommended to the President -- because of 'her sex and age' -- that he reduce Mary Surratt's punishment to life in prison. On July 5, Johnson approved all of the Commission's sentences, including the death sentence for Surratt.
"Surratt's lawyers mounted a frantic effort to save their client's life, hurriedly preparing a petition for habeas corpus that evening. The next morning, Surratt's attorneys succeeded in convincing Judge Wylie of the Supreme Court of the District of Columbia to issue the requested writ. President Johnson quashed the effort to save Surratt from an afternoon hanging when he issued an order suspending the writ of habeas corpus 'in cases such as this.'
"Shortly after one-thirty on the afternoon of July 7, 1865, the trap of the gallows installed in the courtyard of the Old Arsenal Building was sprung, and the four condemned prisoners fell to their deaths. Reporters covering the event reported that the last words from the gallows stand came from George Atzerodt who said, just before he fell, 'May we meet in another world.' "