This is one of those cases where the appellate court sets aside its own previous reasoning. As far as I know, that doesn't actually count as overturning the previous decision... but it does create the sort of conflict that might inspire the Supreme Court to step in at some point. Until then... judges disagree.
So. Smoots was driving drunk, swerved into oncoming traffic, and caused a crash. The driver of the other car was seriously injured, and Smoot was eventually convicted of DUI, DUI per se (his BAC was .346), and vehicular assault. He appealed his conviction.
His argument about the vehicular assault charge was the sort of thing that'll make your brain hurt. He argued that his drunk driving wasn't the proximate cause of the accident because there could have been an intervening cause if the victim driver had been the one to swerve into his lane, and that the jury instructions presented a burden of proof that was too low. The short version of the appellate court's response is that fault isn't relevant for purposes of vehicular assault, the question is whether the defendant was driving drunk and this resulted in a crash. If the other driver were somehow grossly negligent, then that might be an affirmative defense (gross negligence is defined as abnormal human behavior that constitutes an extreme departure from the ordinary standard of care... meaning a lot worse than just drifting out of your lane). But even if the other driver is at fault (or could be at fault), the drunk driver can still be said to have caused the accident for purposes of this statute. And the jury instructions may not have been the best, but they were ok. So the vehicular assault condition stands.
The DUI per se conviction also stands, but the DUI conviction... acknowledging that another division of the court had recently held that DUI is not a lesser included offense of vehicular assault, this division now held that it is. In Medrano-Bustamante, the court had held that because each statute relies on slightly different definitions of motor vehicle, the elements are distinct and so are the offenses. In Smoots, the court now has held that this would be an issue if we were talking about behavior that potentially met one definition but not the other (like driving a boat whilst drunk and hurting someone, which would meet the vehicle definition for vehicular assault but not the one for DUI), but since the behavior in this case meets the definition of motor vehicle use by each statute, the elements are now identical and therefore DUI is a lesser included offense of vehicular assault.
I guess it doesn't really matter much for our purposes, since we can still charge both offenses. One of them would have to be dropped before conviction in order to comply with this decision, but that's something for prosecutors to worry about.