The day Stanley was arrested, Derrick stole his notebook and made Stanley chase after him until he dropped it in a toilet in the boy's lavatory.
When Carla Morengo, Stanley's attorney visited his school, Derrick told her that Stanley was at school fishing his notebook out of the toilet during the time Clyde Livingston's shoes were stolen so Stanley was innocent of the crime. It was Derrick's testimony that helped Stanley be released from Camp Green Lake. Derrick is never mentioned again in the novel. Derrick is also indirectly mentioned by Stanley as "Kids half my size used to pick on me." in Stanley Yelnats' Survival Guide to Camp Green Lake.