Your argument seems to contradict itself. The death penalty is necessary for justice, but at the same time we should be OK with having it because it hasn't been used in a decade?
I don't believe it. Bringing up Charles Manson and using loaded language to describe his avoidance of it clearly makes an argument for the death penalty.
It is a fact that Charles Mason was relieved from execution. Just like it is a fact that because of the court rulings around 1972 he became eligible for parole.
Charles Manson and other 106 inmates on death row in 1972 were all convicted killers who were relieved from the death penalty.
Many victim's family members were upset by the courts decision.