ATLANTA (Reuters) - Georgia will execute a two-time convicted killer on Tuesday if appeals based on the state's ban on capital punishment for those labeled "mentally retarded" fail. Warren Lee Hill, 52, killed a fellow prisoner, Joseph Handspike, in August 1990 by beating him to death. Hill was serving a life sentence for the 1986 shooting death of his 18-year-old girlfriend, Myra Wright. In a series of appeals, Hill's attorneys have argued his execution should be halted because he suffers from what they termed mental retardation. In 1988, Georgia became the first U.S. ...