Given my mischievous youth, I've been quite familiar with the DUI laws here in AZ...
Never got one, though. I consider myself very lucky, and now I don't drive at all after even a sip of alcohol.
As far as the law is written, a DUI can exist even with "the slightest degree of impairment.", which means that you can technically be convicted of a DUI with a BAL of %0.001. This would require a crack team of lawyers and an asshole judge to do, but the books don't limit the minimum to %0.08 like most would like to think.
That being said, the discretion is mostly left in the hands of the officer. The last time I ever drank and drove, which was many years ago, I got pulled over and blew a %0.077. The officer was nice enough to call me a cab, and I thanked him graciously, since he could have made the next years of my life a whole lot worse at that moment. That was all it really took for me.
From what I've gathered, the field sobriety test here is mostly for the officers' personal enjoyment. Whether you fall on your ass or perform the tasks with ease, you're going to get a breathalyser regardless of how well you can perform under the influence.
The funny thing I've noticed in the Scottsdale area is that there is a growing "public brain-trust" of strategies and methods for getting out of DUIs, much like the plethora of half-witted methods people try to use to avoid speed camera tickets. My reply whenever this conversation pops up is, "Don't speed and don't drink drive!". This sentiment is pretty much guaranteed to fall on deaf ears, though...
