Blood alcohol concentration (BAC) is used to set the legal limit for drinking and driving in the United States. It is set at .08% as of this writing. If you do not break that limit, does that mean that you cannot get a DUI?

It does not. Rather than outlawing a certain level of BAC, the law says that you cannot drive while impaired. This is to keep others safe, as there is evidence that impaired drivers cause car accidents. These lead to thousands of deaths and many more injuries every year.

You can be impaired even before you get to the legal limit. You may cause an accident, fail field sobriety tests or give the officer some other reason to decide that you are impaired. This can still lead to an arrest, as the alcohol has now impacted your ability to drive in the officer’s opinion.

Coming in under .08% may help your case. If you blow over that, the law presumes you were impaired. If you blow under it, you can argue that the officer is wrong and that you were not impaired. A low enough BAC may get you out of the charges, and this does mean that it becomes the officer’s duty to prove your impairment. Once you hit that legal limit, things change because the court looks at the BAC reading as proof enough.

When you feel like you did not suffer impairment and your BAC supports that, but the officer arrests you anyway, things can grow very complicated. You need to know your legal options.