Were I to argue in front of the Supreme Court (and I confess I have no idea what I'd wear) I would take the position that Life Imprisonment without the possibility of parole is Cruel and Unusual.
If we're going to tell someone that the crime he/she has commited is so heinous and despicable that they don't deserve to ever taste freedom again, but then take the position that we'll do everything in our power to keep them alive, well...at that point we're being Cruel, though sadly not Unusual.
If they develop diabetes, we'll give 'em shots to keep 'em alive....and imprisoned.
If they have a heart attack, we'll slap some defibrillators on 'em and zap 'em back to life.....so we can watch that life slowly eaten away.
If they break a leg, we'll fix it.
...take out a gall bladder or kidney or whatnot.....
...anything we can, in short, to keep them alive and...., well and what actually? Penitent? Please.... there's a reason they're not called Penitentiaries any longer. Few of them are penitent (check your local recidivism rate).
Answer: alive and Suffering.
That implies something a bit different than justice, an eye for an eye, say. The Suffering bit implies Hatred, Evil even, if ya believe in that sorta thing.
No, I think I'd rather just execute them and have done with it. Do away with Life w/out poss. of parole and get rid of 'em.