As the organizer of internal security, Edwin M. Stanton was blamed for the assassination of Abraham Lincoln on 14th April 1865. Stanton immediately summoned Lafayette Baker, head of the National Detective Police (NDP) to Washington with the telegraphic appeal: "Come here immediately and see if you can find the murderer of the President." Baker arrived on 16th April and his first act was to send his agents into Maryland to pick up what information they could about the people involved in the assassination.
Within two days Baker had arrested Mary Surratt, Lewis Paine, George Atzerodt and Edman Spangler. He also had the names of the fellow conspirators, John Wilkes Booth and David Herold. When Baker's agents discovered had crossed the Potomac near Mathias Point on 22nd April, he sent Lieutenant Edward P. Doherty and twenty-five men from the Sixteenth New York Cavalry to capture them.
On 26th April, Doherty and his men caught up with John Wilkes Booth and David Herold on a farm owned by Richard Garrett. Doherty ordered the men to surrender. Herold came out of the barn but Booth refused and so the barn was set on fire. While this was happening one of the soldiers, Sergeant Boston Corbett, found a large crack in the barn and was able to shoot Booth in the back. His body was dragged from the barn and after being searched the soldiers recovered his leather bound diary. The bullet had punctured his spinal cord and he died in great agony two hours later. Booth's diary was handed to Lafayette Baker who later passed it onto Edwin M. Stanton. Baker was rewarded for his success by being promoted to brigadier general and receiving a substantial portion of the $100,000 reward.
On 1st May, 1865, President Andrew Johnson ordered the formation of a nine-man military commission to try the conspirators involved in the assassination of President Abraham Lincoln. It was argued by Edwin M. Stanton, the Secretary of War, that the men should be tried by a military court as Lincoln had been Commander in Chief of the army. Several members of the cabinet, including Gideon Welles (Secretary of the Navy), Edward Bates (Attorney General), Orville H. Browning (Secretary of the Interior), and Henry McCulloch (Secretaery of the Treasury), disapproved, preferring a civil trial. However, James Speed, the Attorney General, and Joseph Holt, the Advocate General of the Army, agreed with Stanton and therefore the defendants did not enjoy the advantages of a jury trial.
The trial began on 10th May, 1865. The military commission included leading generals such as David Hunter, Lewis Wallace, Robert Foster, August Kautz, Thomas Harris and Albion Howe. The Attorney General, James Speed, selected Joseph Holt and John Bingham as the government's chief prosecutors.
Mary Surratt, Lewis Paine, George Atzerodt, David Herold, Samuel Mudd, Michael O'Laughlin, Edman Spangler and Samuel Arnold were all charged with conspiring to murder Lincoln. During the trial Joseph Holt and John Bingham attempted to persuade the military commission that Jefferson Davis and the Confederate government had been involved in conspiracy.
Joseph Holt attempted to obscure the fact that there were two plots: the first to kidnap and the second to assassinate. It was important for the prosecution not to reveal the existence of a diary taken from the body of John Wilkes Booth. The diary made it clear that the assassination plan dated from 14th April. The defence surprisingly did not call for Booth's diary to be produced in court.
On 29th June, 1865 Mary Surratt, Lewis Paine, George Atzerodt, David Herold, Samuel Mudd, Michael O'Laughlin, Edman Spangler and Samuel Arnold were found guilty of being involved in the conspiracy to murder Abraham Lincoln. Surratt, Paine, Atzerodt and Herold were hanged at Washington Penitentiary on 7th July, 1865. Surratt, who was expected to be reprieved, was the first woman in American history to be executed.
The decision to hold a military court received further criticism when John Surratt, who faced a civil trial in 1867, was not convicted by the jury. Michael O'Laughlin died in prison but Samuel Mudd, Edman Spangler and Samuel Arnold were all pardoned by President Andrew Johnson in 1869.
The commission has collectively an imposing appearance: the face of Judge Holt is swarthy; he questions with slow utterance, holding the witness in his cold, measuring eye. Hunter, who sits at the opposite end of the table, shuts his eyes now and then, either to sleep or to think, or both, and the other generals watch for the occasions to distinguish themselves.
Excepting Judge Holt, the court has shown as little ability as could be expected from soldiers, placed in unenviable publicity, and upon a duty for which they are disqualified, both by education and acumen. Witness the lack of dignity in Hunter, who opened the court by a course allusion to "humbug chivalry", of Lewis Wallace, whose heat and intolerance were appropriately urged in the most exceptional English; of Howe, whose tirade against the rebel General Johnson was feeble as it was ungenerous! This court was needed to show us at least the petty tyranny of martial law and the pettiness of martial jurists. The counsel for the defense have just enough show to make the unfairness of the trial partake of hypocrisy.
The undersigned members of the Military Commission detailed to try Mary E. Surratt and others for the conspiracy and the murder of Abraham Lincoln, late President of the United States, do respectively pray the President, in consideration of the sex and age of the said Mary E. Surratt, if he can upon all the facts in the case, find it consistent with his sense of duty to the country to commute the sentence of death to imprisonment in the penitentiary for life.
It must be remembered that on the night of 17th April Payne returned to her house, with pick-axe on the shoulder and cap made from his shirt sleeve on his head.
The very act of this red-handed murderer fleeing to her home at such a time, was in itself, the strongest and most damning evidence against her.
Take away these two items of evidence - the terrible story of the shooting irons and Payne's return, wipe them out, remove them for the record, and Mr. Weichmann's evidence as to what he saw and heard in Mrs. Surratt's house falls harmlessly to the ground.
Although Lloyd's testimony was most damaging against Mrs. Surratt, and probably condemned her, he himself never believed in Mrs. Surratt's guilt, and said she was a victim of circumstances. Her association with the real conspirators, he always held, was the cause of her conviction.
I was determined to get rope that would not break, for you know when a rope breaks at a hanging there is a time-worn maxim that the person intended to be hanged was innocent. The night before the execution I took the rope to my room and there made the nooses. I preserved the piece of rope intended for Mrs. Surratt for the last.
I had the graves for the four persons dug just beyond the scaffolding. I found some difficulty in having the work done, as the arsenal attaches were superstitious. I finally succeeded in getting soldiers to dig the holes but they were only three feet deep.
The hanging gave me a lot of trouble. I had read somewhere that when a person was hanged his tongue would protrude from his mouth. I did not want to see four tongues sticking out before me, so I went to the storehouse, got a new white shelter tent and made four hoods out of it. I tore strips of the tent to bind the legs of the victims.
The prison door opened and the condemned came in. Mrs. Surratt was first, near fainting after a look at the gallows. She would have fallen had they not supported her. Herold was next. The young man was frightened to death. He trembled and shook and seemed on the verge of fainting. Atzerodt shuffled along in carpet slippers, a long white nightcap on his head. Under different circumstances, he would have been ridiculous.
With the exception of Powell, all were on the verge of collapse. They had to pass the open graves to reach the gallows steps and could gaze down into the shallow holes and even touch the crude pine boxes that were to receive them. Powell was as stolid as if he were a spectator instead of a principal. Herold wore a black hat until he reached the gallows. Powell was bareheaded, but he reached out and took a straw hat off the head of an officer. He wore it until they put the black bag on him. The condemned were led to the chairs and Captain Rath seated them. Mrs. Surratt and Powell were on our drop, Herold and Atzerodt on the other.
Umbrellas were raised above the woman and Hartranft, who read the warrants and findings. Then the clergy took over talking what seemed to me interminably. The strain was getting worse. I became nauseated, what with the heat and the waiting, and taking hold of the supporting post, I hung on and vomited. I felt a little better after that, but not too good.
Powell stood forward at the very front of the droop. Mrs. Surratt was barely past the break, as were the other two. Rath came down the steps and gave the signal. Mrs. Surratt shot down and I believed died instantly. Powell was a strong brute and died hard. It was enough to see these two without looking at the others, but they told us both died quickly.