Unfortunately the Constitution prevents “...Cruel and unusual punishment...”
To me that means only punishments which are both cruel AND unusual are prohibited.
However, the Courts have interpreted that as meaning such punishments from the category “cruel” and the category “unusual” are prohibited. The “and” is interpreted as “or.”
Under my theory there could be cruel or unusual punishments just not both.
If they don’t keep him in solitary confinement I suspect his fellow inmates will arrange a chance meeting with some concrete.