For those opposed to the death penalty. What is the just punishment for a murderer who goes on to kill someone in prison
I say place a noose in his cell and put him on the Mooch Obama diet. Let him take care of himself one way or the other. Slow starvation or hanging.
In my world, the same as for multiple murderers: Kill 'em more than once.
Lethal injection is fine. At 7 a.m. (pick any time, as long as it is consistent) the guy on the gurney is given Last Rites a la "Seconds" (at 4:40) and rolled into The Room.
Blackness.
Light - as he wakes up in his cell the next morning. The bars slide back and The Men With The Gurney come in and he is told the process would be repeated until his trips equal those he killed - or not. The kicker is that he doesn't know which trip is his last.
If his crimes were particularly heinous or involved children, he'd undergo The Treatment a few more undetermined times. It would only stop when he was so mad with fear he no longer understood what was happening - or because the executioners got tired of listening to the noises he made.
The Word is passed around and prison killings and multiple murders drop to single digits.