Welcome Home Brother Charles (1975)
Whether or not our protagonist Charles is subject to experimentation while in prison is subject to debate. His behavior after parole indicates otherwise, and the prison dream sequence seems to indicate that the cause of his prehensile murdering manhood is magical or spiritual in origin, as opposed to a freak effect of science.
AKA: Soul Vengeance
Directed By: Jamaa Fanaka
Written By: Jamaa Fanaka