Duke is a laid back and easy going guy. He is not very strict and has an open minded personality. Friendly and warm hearted, he is easy to get along with. Duke even has the patience to put up with Frank and his antics.
Duke is the uncle of Ellie Phillips, who, during the events of Lego City: Undercover, works in Cherry Tree Hills at the main police department ran by Chief Dunby. His sister is the mother of Ellie. Duke does not work in Lego City two years before the events of Lego City: Undercover. During that period, it is possible that Duke worked outside of Lego City and moved with Ellie and possibly other family to Lego City after the events of Lego City Undercover: The Chase Begins.
In Lego City: Undercover, Duke can be found working at the police station in Bluebell National Park where he is the only one on duty there. He looks out for the park, the woods, and the mine. Duke never plays an important part in the story and he is only briefly referenced.