The three, all trained boxers from Sunderland, repeatedly punched, kicked, stamped on and head-butted their victim over a £5 bet to see who could knock him out first.
They chased him around the Town End Farm estate just three months after he was released from a psychiatric hospital where he had been staying due to his learning difficulties, the court heard.Finally he was stripped of his trousers and pants and left dying next to a parked car in Baxter Road, Town End Farm, as his attackers posed for photographs.
A post-mortem examination revealed Mr Martin died from a massive head injury and had suffered at least 18 separate blows to the head and neck.
Hughes, from Washington Road, must serve a minimum of 22 years, Bonallie, from Birtley Avenue, 18 years, and Miller, from Baxter Road, must serve at least 15.Judge John Milford described the attack as "sadistic conduct on an extremely vulnerable victim".
He said: "I would hope the minimum terms imposed upon young offenders are sufficiently long to spell out to young people the consequences of committing murder."If I am wrong, then perhaps the 12-year starting point for those under 18 needs to be looked at again by Parliament when the murder is, as in this case, particularly serious."