Cruel and Unusual or Fair and Justifed?

I recently read an article that discussed the Supreme Courts discussion on “whether the Constitution's ban on “cruel and unusual punishment” should be applied in such cases” as the case from West Kensington Philadelphia where a 17 year old boy beat, raped and murdered a twelve year old neighbor.
The topics in their discussion will deal with whether or not it is constitutional to limit “a state's ability to impose incredibly tough sentences on either the young, or in some cases, the mentally retarded," stated Thomas Goldstein, a leading Washington attorney. They also are posing the question, should a minor be able to receive a life sentence with no parole?
In my opinion, I think that someone of that boys age knows right from wrong. He obviously knows its not right to abduct his twelve year old neighbor and beat, rape and kill her. I think he deserves to spend the rest of his life in jail because he took the life away from a little girl and he should give up his own life for the loss of hers. I think that a minor should be able to receive a life sentence because older teens such as 16 or 17 year olds are capable of thinking like an adult and shouldn't be babied in court after they have done something as horrible as murdering someone. However, I do not think those who have mental disabilities should have the same sentencing. I think a minor with a mental disability, in some cases, don't know what is right from wrong as a person the same age would.
Should a minor be able to receive a life sentence without parole? Do you think it is constitutional to do so?