Many 8 year olds don't comprehend death. Many 8 year olds do things like spin in a chair when they are very nervous. This web site describes some of the psychological development that 8 year olds are experiencing.
http://childparenting.about.com/od/c...aroldhom_2.htm
http://childparenting.about.com/od/c...aroldhom_3.htm
As you can see, things like understanding right from wrong and feeling guilt are just developing at 8. I don't see how we can possibly try an 8 year old as an adult. It's just ludicrous. He needs psychological help. When he comes to understand that his dad will never come back and that it's his fault, he's probably going to be seriously traumatized.