The oldest of four children, Chapman was raised in a tough and poor environment. During his youth he lived in Texas and other parts of the United States and pursued an active life in crime. Chapman dropped out of school in the ninth grade and joined the Devil's Disciples motorcycle gang.
Chapman has been arrested 18 times for armed robbery. In 1976, he and other members of the Devil's Disciples were arrested for the murder of a local pimp and drug dealer. Although Chapman insisted that a fellow gang member had acted alone in killing the man, he was found guilty for his alleged role in the murder.
In 1977, he was sentenced to five years of intense labor. While serving time in a Texas state penitentiary, Chapman turned to Christianity and swore to reform his life (his nickname is "God" spelled backward). After only two years behind bars, Chapman was given parole.