I support part of what you say – this is a damaged young man  -  but aren't most people in prison damaged young and old man and damaged women to?. My own belief is that -  unless there is a VERY  good reason to find them not responsible for is ending up in foster care, then his birthparents should also be  brought to the bar of justice as well. In fact, it would not bother me at all to see legislators consider this kind
" criminal neglect (?)"  legislation with crime time! 
 I also had a BIG problem with the drunken,  repeat-offender, hit-and-run daughter of the bar association member "skating" on her killing of the bicyclist - but while her crime  deserved far  more severe penalties, it was not intentional murder – this case was.
 And we have neither a place nor money  money to heal those childhood wounds  with treatment-  all we can do is lock them up for our safety.