It's no fun seeing the blue lights in your rear-view mirror, even if you've had nothing to drink. But if you've had even as much as a beer, your breath could have more "alcohol odor" than a person who had seven vodkas.
Despite all of the pretending that a DUI investigation is scientific, it is anything but. There are essentially three things that will cause the police to take you into custody: the slightest mis-speech or misstep, the smell of alcohol and the standardized field sobriety "tests."
1. Mis-Speech or Misstep.
This is why you have to be careful. Your driving may be perfect, but they pulled you over for something. If you have "alcohol" on your breath, then you are half-way to jail already. It doesn't take much to convince the police that you are DUI. If you touched the lane marker even once (and who doesn't?) you must act quickly and decisively to make sure that you are not swept up with those who truly are guilty.
Say as little as possible. When we are nervous, many of us run off at the mouth. The more you blab, the more likely that you are going to be spending the night at the Handcuff Hilton. A slight slur, or forgetting the name of a person or place, and the police will write in their report that "subject's speech was disjointed."
Do as little as possible, too. Don't walk or talk unless you have to. The police will often suggest that people take off their shoes, as if that will make them more comfortable. Don't fall for this. Being barefoot might be comfy on your living room carpet, but in a concrete parking lot with pebbles and acorns lying about, it is highly likely that you will step on something which will make you stumble.
2. The Smell of Alcohol.
The police nearly always note "the smell of alcoholic beverage" in their police reports. The reason that they put it that way is that drinking alcohol--Ethanol--has no odor. Nobody can smell alcohol. Rather, what we refer to as the smell of an alcoholic beverage is the smell of the by-products of the fermentation process--esters, phenols, aldehydes, and the like.
So they aren't smelling alcohol, and the strength of the smell has no relation to the amount of alcohol consumed. A person who has consumed one O'Doul's near-beer will have a stronger "odor of alcohol" than a person who has consumed three vodkas.
3. Standardized Field Sobriety Tests
Important thing to remember--The Field Sobriety Tests are BUNK.
There are three Standardized Field Sobriety Tests that have been "validated" by the U.S. Department of Transportation. They are all bogus. Not one has ever been tested double blind, and not one has ever been subjected to peer review. Double-blind testing and peer review are the hallmarks of real science, and police science is not real science.
In fact, the National Highway Traffic Safety Administration (NHTSA) recently released the raw data for a study it did in 2007 to bolster the "Horizontal Gaze Nystagmus Test." The agency deliberately set out with an agenda--to prove that the test was reliable even when the police did it wrong. I kid you not. What the study proved is exactly the opposite.
The agency made the mistake of publishing their raw data for the first time. What they showed was that, even when the test was done correctly, the HGN test led to the arrest of most of the drunk people--and most of the sober people, too. The study started with 36 subjects, with varying amounts of alcohol on board. Of the 26 subjects whose breath/blood alcohol was under .08--the legal limit--the HGN test said that the police should arrest 20.
Let me say that again--the HGN test, properly done, would have led to the arrest of 20 out of 26 legally sober people. According to NHTSA's own data. If you want to see it yourself, click here.
The thing to remember about the field sobriety tests goes back to Item #1 above. Don't do anything more than you have to.