If you are old enough to commit an adult crime, you are old enough to do adult time. A person that is stabbed to death by a 13 year old is still just as dead as one stabbed to death by an 18 year old. Chances are what got him the life in prison sentence was premeditation and lack of remorse. The same thing that would get an adult sentenced to life without parole.
"I would rather be exposed to the inconveniences attending too much liberty than to those attending too small a degree of it." Thomas Jefferson