A good chunk of you figured out that if the horsemen were to ride each other's horse, then the horse belonging to the race winner would come in second, making him the "winner", according to the king's rule. Now, let's see how good a detective you are:

James Diamond waited until Ari Gant left the office of author Karry Queen. Diamond slipped on a pair of gloves, took a handgun from his desk, and crossed the hall to Queen's office. As Queen glanced up to see the intruder, Diamond took aim and shot. Diamond dropped the gun on the floor, picked up the telephone on Queen's desk, and called the police. He then went back across the hall to his office and hid the gloves. Shadow arrived moments later and Diamond recounted the events. "I was working at my desk when I heard a shot. I ran to the hall and saw a man fitting the description of Ari Gant running away from Queen's office. I went to Queen's office and found him sprawled on the floor, dead. I immediately picked up the phone on Queen's desk and called the police." Several hours later, Shadow ordered Diamond arrested for murder. Why was he so easily caught?