His attorney would appeal and he'd be dead before anything happened. But who'd be punished? The taxpayers of LA who'd have to bear his medical costs if he did do time. This is just one of those hopeless lose-lose situations.
Seniors should be given a behind-the-wheel road test at least once a year to prevent exactly this type of scene that happens entirely too often, alas, with far less damage in most cases.
Actually, there are very realistic driving simulators that would work well for this. I was watching a show the other night about U.S. soldiers recovering at a brain injury unit in California. They used the driving simulator to retrain and test basic skills and reactions of the injured. Something like that would be perfect.