SOP for those of us who are known to occasionally imbibe: PUT THE KEYS IN THE TRUNK!!! Everybody down here knows that. I believe the issue here is intent. They'll say that you were planning on driving off and fortunately passed out before you could kill a family of 9. Honestly, I'm sure there are some cops who'll cut you some slack in that situation, but considering what a monumental racket DUI arrests are, I wouldn't count on much discretion. Too much money to be had.
She's just lucky that the cop was stupid enough to do it whilst on camera. Down here, everybody resists arrest on the elevator ride up, where nobody can see.
Edit: Portrucci did hit on an interesting point. Johnny couldn't let her drive off if he suspected her to be intoxicated. Presumably she was in a place where she couldn't continue to sleep it off either. This puts him in a strange situation that made that aforementioned discretion quite a challenge. Cutting her some slack would have been a real PITA for him since he has to do something to resolve the situation. Popping her for the DUI gets him a gold star, the state gets their 10 grand, and he doesn't have to figure out a way to get her home. To be clear, I think citing people for DUI when they were actually trying to avoid it is bullshit. I just understand why he wouldn't feel to compelled to search for an alternative.