Duke was formerly a vicious punk who terrorized Metro City as "Mad Duke". He eventually decided to work for the good of the city and became a NYPD detective along with his friend Billy King. They were investigating on the Yakuza (a Japanese crime syndicate), when they became their targets. They were joined by Ryu Saeba, a martial arts master and decided to fight the Yakuza.
He likes to live his life without worries and he loves to fight. He is regretful of his past actions and is still mailing apologetic letters for the victims of his "Mad" days.
He has good kicks and punches. His fighting style is probably based on Karate mix with Boxing. His signature technique is the "Submarine Screw", a twirling Dragon Punch-esque uppercut.