Out in 9 years. No problem.
The trial will probably take that long.
Unless he's treated like the youngster who killed the 6 year old girl by body slamming her until she died. Civil rights groups whined until he was turned loose and he's been in trouble with the law ever since. They can send the kid to "treatment" until he's 21, but his parents ought to be in jail forever!
I remember a news years ago there were two 10 year old boys from Britain who murdered a toddler. They got jail terms to the time they were of age (21). Rumours were that both had their identity completely changed when released and at one point the British government considered forcing them immigrate to one of the "old" Commonwealth countries (Canada, Australia, New Zealand). Of course each of these countries rejected the plan.
Had these two young men made it to Canada, I promise there would be two new criminal elements in America soon afterwards. I wonder what this 12 year-old will fare?
Probably out after 4 years of "self-esteem" councelling. By then he will have so much "self-seteem" that he will feel entitled to kill people right and left.