I know not all children are on the same level. But the fact that he is 8 means either:
1. [If he did it] He will be treated as a juvenile and the confession will be tossed.
2. [If he didn't do it] He will be treated as a juvenile and the confession will be tossed.
There is no need for an insanity diagnosis/plea.
I agree. The confession is meaningless. The case is going to depend on physical evidence.
The videotapes of parts of the confession really throw this into question regardless of the legal details (need for legal guardian being present, etc). In the middle of his confession he pops up with the question, "Shot who?" The confession will never be seen in court, but probably still shouldn't have been shown on TV if there's a chance this case will ever go to court.
Supposedly, the police had responded to calls about domestic violence in the home in the past, although they didn't have any idea how recently when asked by reporters. The boy knew how to use the gun. That's about the extent of the case as far as has been released to the public.