Although a staunch friend and ally of Abraham Lincoln, when Edwin Stanton engaged in a post-assassination flap with Ewing's brother-in-law William T. Sherman over final surrender terms to the Southern armies, Ewing agreed to represent two of John Ford's (of Ford's theater) employees in the Lincoln conspiracy trials. Through Orville Browning, Ewing's Washington law partner, Dr. Samuel Mudd's family also sought Ewing's legal help. Ewing also represented Samuel Arnold and Edmund Spangler during the trial. Ewing's efforts kept all three men from the gallows, but other conspirators were hanged. For their roles in the assassination, Mudd, Arnold and Spangler were sentenced to federal prison at Fort Jefferson in the Dry Tortugas off Key West, Florida.