Parole for "Onion field" killer

The onion field killer is up for parole from a life sentence, he has served almost 50 years now but, is that enough? Don't froget that he murderd police officer Campbell in cold blood. I personaly think and say that he should not be allowed parole! He has been up for this for the 12th time now and he shouldnt be allowed to be free. He deserves a life sentence and thats what he has.