Are Children Different?

So my client was found guilty of second degree murder with enhancements for firearm discharge, gang-relatedness, and shooting from a car. Also attempted murder (with the same enhancements), shooting at an occupied dwelling (multiple counts, with the same enhancements), etc., etc.

Now that's been decided, the next question is; does the United States Constitution permit a sentence of life without parole for crimes committed when the defendant was fourteen years old? Sometimes? Never?