That is one of the difficulties of the American system of governance. We have codified that no punishment can be cruel or inhumane. That holds even when the crime is both cruel and inhumane. On the basis of that we can, in many cases, not provide a punishment that actually fits the crime. That is why in response to the torture question my answer is perhaps.
The measure of "cruel and inhumane" has be fixated upon to create the "luxury" prisons that now are de rigueur. There is no real punishment in prison, merely an inconvenience.