Chasing Lincoln's Killer Practice Test

Being a physician by trade points to Dr. Mudd. He was a doctor who treated John Wilkes Booth’s broken leg at his farmhouse after Booth fled Ford’s Theatre, which linked him to the conspiracy. The other individuals listed were not physicians—Mary Surratt ran a boardinghouse, Edmund Spangler was a stagehand who helped Booth’s escape, and George Atzerodt was a conspirator who plotted against the vice president but did not practice medicine. So the one who fits the description of a conspirator with a medical profession is Dr. Samuel Mudd.