Who is Stephen Byerley from the novel, I, Robot?

Stephen Byerley is a politician who was once accused of being a robot. Byerley is reported to have been in a devastating car accident as a young man and to have created a robot to take his place so that he might continue with the work he once dreamed of doing. Byerley seems to prove himself human by hitting a man after giving a speech, but Dr. Calvin theorizes that if Byerley’s creator could make him, he could have made another robot so that Byerley could appear to have cleared any doubts of his humanity without breaking the laws of robotics. Later, Byerley is elected the World Coordinator, the ruler of all the world. When Byerley dies, he has his body destroyed to take away any chance of someone investigating and learning the truth of his nature.