The case is not as straight forward as some would seem. The kid is claiming seld defense because its all he can claim. He can not deny he shot three unarmed people at close range. And he can't deny he intended the kill them.
Thd jury must decide only one point to find him innocent or guilty. "Did he establish the conditions in which he had to kill thd two other men" (and shoot a third) or was it a turn of events.
The argument comes down to a simple (if simple were only that simple) - If he put himself in a position where he had no choice but to shoot, he's guilty.
Personally I don't believe that an underage kid had any business driving hundreds of miles across state lines, without a driver's license, with a semiautomatic rifle, thats illegal for him to own in Illinois, and injecting himself into a volatile situation with a loaded gun. The other men there who were assisting law enforcement, also felt he was too young and tried to keep a eye on him. Guiding and mentoring him.
I'm guessing that we'll find out, one way or another, later today.