I recall reading once, that the death penalty, on average, saves seven lives for every execution. Executing one murderer saves seven innocent lives.
We have numerous cases of convicted murderers being released, and killing again. Especially those convicted of 2nd degree murder, often in a plea deal, who are released in their forties, and who go out and kill again. Very, very common.
Civil society must deal with miscreants up to keeping unrepentant dangerous behind bars in protection of society. But the death penalty is not now in the “justice” equation. It is only in the unjust “vengeance” equation.