While the threshold for a DUI is .08% blood alcohol, you can also get a DUI if you’re under 0.08%. When the officer stops your car, they’re really just looking for one thing: evidence of impairment. If your ability to drive safely is impaired by alcohol, no matter how much you have had, then you have broken the DUI laws. You can get arrested.
The legal limit just exists to make things easier for the police and the courts. With proof of a BAC that is over the limit, impairment is assumed by the court. The officer doesn’t have to prove that you were visibly impaired. All they have to show is that there was a valid reason for the stop and that you were over the legal blood alcohol limit.
If your BAC is under 0.08%, the court does not assume you were impaired. This doesn’t mean you were not. It just means that the assumption isn’t made and so the officer must present other evidence to show that you were. You can still get convicted, and being under 0.08% does not automatically get you out of the charges.
If you’re surprised by this and/or facing DUI charges right now, it’s critical to protect yourself. Speaking with an experienced criminal defense attorney before you speak with the police is the wisest decision you can make.