By most accounts, Arthur Garfield Hays was the defense team's manager, developing the overall strategy of the defense. Hays, a longtime defender of unpopular causes for the ACLU, was known as an expert on technical aspects of law. Hays was in charge of keeping the record in shape for appellate review.
The short and stocky Hays, named after three presidents, made his living off a corporate practice in New York, but seemed most drawn to society's underdogs. He was described as a person of "genuine sympathy and understanding."
Hays also played key defense roles in the Sacco-Vanzetti case and the burning of the Reichstag trial. He authored two novels, Let Freedom Ring and Trial by Prejudice, as well as an autobiography, City Lawyer.
Hays saw the Scopes trial as an opportunity to educate the public. He said, "the people of the country learned more about evolution through the Dayton exhibition than they could have in any other way." At the close of the trial, Hays offered to send Judge Raulston a copy of The Origin of the Species. The judge laughingly agreed to accept it.