Marvin Wilson was convicted of fatally shooting a police drug informant nearly 20 years ago. He was then sentenced to death by lethal injection, but the U.S. Supreme Court soon afterwards found the penalty to be in violation of the constitution’s ban on cruel and unusual punishment when imposed on the mentally retarded. Wilson's lawyers say is clinically "mentally retarded". Simon Whitaker, a clinical psychologist from the UK, told Al Jazeera: "This is a miscarriage of justice, he [Wilson] would have the same reasoning powers of a five-year-old child, if a five-year-old child killed someone we would not execute them in part."