Cooper, who has a history muddied with robberies, was also sentenced for the rape of a 16-year-old girl and a sexual assault on a 15-year-old girl, both carried out at gunpoint, in March 1996.
In September 2011, he launched an appeal against his convictions. His appeal was rejected in November 2012.
On embodying the brutal killer, Allen explained: “I guess I’ve just got those eyes – murderer’s eyes.
“It was really good to be involved in something that required me to act, rather than just be me.”