Sam Pritchett is a convicted criminal who appeared in Lockdown as a suspect in a series of killings.
Background
No specific information was revealed about Sam, including how he became an inmate at the Reagan Federal Penitentiary. He was one of many inmates forced by Dale Shavers and his gang into fighting for them. Sam befriended a new inmate named Devon White, who helped smuggle him books from the library after prison guards took his previous books away. When Devon was accidentally killed by Patrick Butler during a fight set up by Shavers, Sam was forced by Randall Jefferson Jones, another inmate assisting Shavers, to remain silent about the whole thing.
Lockdown
Sam was one of several inmates interrogated by the BAU when they investigated Devon's strange disappearance. He tells Rossi of how he befriended Devon, but refuses to answer his questions about any involvement. Later on, Sam is approached by Rossi, who tells him the books taken by the prison guards were recovered downstairs. He gives them to him in a box, and Sam thanks him. Rossi tells him to "take care of [him]self" before leaving.