Boyle entered the practice of law in Idaho Falls with the law firm of Hanson, Boyle, Beard and Martin, until 1986, when he was appointed to a seat on Idaho's 7th District bench.[6] He also served as president of the 7th District Bar Association, and as a member of the Idaho Judicial Council, which made recommendations on the appointment of judges.[3] While serving as a district judge, Boyle was called up to fill in on the Idaho Supreme Court on several occasions.[3] In 1989, Governor Cecil Andrus appointed Boyle to the state supreme court,[4] which was well-received even by political opponents of the governor.[3]