[GeorgNihilus]

Let's just suppose we (law) allow his freedom at let's say ... 23 (sentence, parole, whatever). And he does it again, killing. What are we going to say to the next victim? we had the chance to lock him up and we (society-system) allowed his freedom. Just 13 years old when doing it but he killed, and in that way. Worst, these cases usually do stablish precedent for further trials; so from the moment we allow this boy's freedom and case is closed, many other similar cases will be solved same way.

Nevertheless, I don't agree with capital punishment; less at this age, so maybe life imprisonment is the unique choice for cases like this. Of course it's expensive for a society to feed people for 15, 25 or 50 years ... but it's the only choice IMHO. More prisons maybe too.