It's very shameful the defense is putting down tracks to blame the victim and her memory of the events. No doubt they are also trying to build a foundation to keep a crafty teen in juvenile court. Seems to me that the defense forgot to listen to their clients own words to the 911 dispatcher. Not difficult to determine which party is the story teller here. JMO
I would imagine they don't have a choice. If the boy is insisting that his brother was the shooter, then they have to make those arguments.
But we're a long way away from any trial. The accused will eventually have to come to terms with the fact this his 'perfect crime' was a failure and he will not be walking away scot-free. I suspect he has very little idea of how advanced modern forensics are and how investigators will be able to scientifically prove he was the killer. After all, not many teens watch "Forensic Files". It will likely be on his attorneys to walk him through the evidence, show him that the prosecution has an irrefutable case, and a defense that 'someone else did it' will fail. It will be a long, arduous task for them to convince someone who may not be entirely rational, and I don't envy those attorneys.