The special prosecutor in the 1984 murder trial of a Montana prisoner serving a 100-year prison sentence for a killing committed when he was 17 says the case has been exhaustively reviewed and the state parole board should reject a recent plea for clemency.

Barry Beach was sent to prison without the possibility of parole for the 1979 beating death of Kim Nees near Poplar. The high school classmates were 17.

Former Montana Attorney General and Gov. Marc Racicot, who was the special prosecutor in Beach's case, wrote to the Board of Pardons and Parole on Tuesday. That same day during a hearing in Deer Lodge, Beach's supporters argued that he should be eligible for parole because young criminals can no longer be sentenced to life in prison without the possibility of parole under a 2012 U.S. Supreme Court decision.

Beach was released for 18 months after a judge ordered a new trial, but the state high court overturned that decision and he returned to prison last year.

Beach's September 2013 clemency application states that new evidence casts more doubt on his conviction. Beach is no longer arguing his innocence, but that circumstances have changed since his last clemency request was rejected. Besides the U.S. Supreme Court decision and new scientific research showing juvenile offenders can change, supporters say he showed model behavior in prison and when he was free.