 O'Laughlen was tried along with Mary Surratt, Lewis Powell, George Atzerodt, David Herold, Samuel Arnold, Edmund Spangler and Samuel Mudd.The government attempted to prove he had stalked Ulysses S. Grant on the nights of April 13 and April 14 with the intent to kill and murder.This was not proven, but there was no doubt O'Laughlen was a willing conspirator through late March.