William "Bill" Preston is a former soldier who was with Seeley Booth in Afghanistan. He was a suspect for the murder of Heather Taffet but he said that he had not killed Taffet because he was on assignment. He points the finger at Jacob Broadsky, who was his mentor for ten years and instructed him in close quarter combat before they went to Dallas HRT together.
He is ambidextrous, hunts, and likes black coffee.