. . . unless the kidney damage is permament. In that case, 20 years to life would be in the ballpark. If the kid dies, try them all for murder-one (although the conviction would likely come back at murder-two).
And a notice posted on their cell door informing the rest of the inmates as to the particulars of their crime. It is a pity that so many times we must rely on prisoners to exact the punishment the State should be meting out.