I remember watching a sci fi film which was set in space. An all female crew were sent to a prison colony to rescue the guard (I think there had been a riot). Upon arrival there were two people still alive, one identified as a guard and one identified as a prisoner. Both of them claimed to be the guard. One by one the crew were killed. I think the film was called 'Prisoner XXXX' (the four X's being his number).
Any help is greatly appreciated.