Constitutional doctrine relating to capital punishment is (in)famously tangled. That said, one proposition that, I suspect, most who litigate, teach, or write in the area have long thought -- since Coker v. Georgia (1977), anyway -- one could take to the bank is that the death penalty is an unconstitutional punishment for non-homicide crimes. The New York Times is reporting, though, that the Louisiana Supreme Court has "upheld the death sentence of a man convicted of raping an 8-year-old girl. Legal experts say the man, Patrick Kennedy, is the only inmate on death row in the United States who was not convicted of committing or participating in a killing."
It is quite likely that the Supreme Court will review the Louisiana court's decision. In Coker, the Justices ruled that the death penalty for "the rape of an adult woman" is "grossly disproportionate and excessive punishment" and "therefore forbidden by the Eighth Amendment as cruel and unusual punishment." Can the same be said -- should the same be said -- of the death penalty for the rape of a child?