If you get pulled over for drunk driving, you should be very mindful of your behavior. Even in instances where you can demonstrate that your blood alcohol level does not exceed the legal limit, a police officer may still charge you with being "under the influence."
"Under the influence" does not necessarily mean that you are over the legal limit. Rather, it implies that the officer has the discretion to charge you if he or she has reason to believe it unsafe for you to operate a vehicle in your current state, even if you pass a breathalyzer or other chemical blood alcohol content test.
In this instance, you may be legally sober, but the officer believes that you are not practically sober. The officer may also believe that you are operating under the influence of a controlled substance. Be mindful that even if you can pass a chemical sobriety test, if you cannot prove that you are in reasonable control of your reflexes, you may still be arrested.
The key to these kinds of charges lies in demonstrating your impairment, or lack thereof. If you are driving erratically and get pulled over, for instance, you get a DUI charge primarily based on your behavior. In some cases, simply driving while very sleepy may prove enough to justify some sort of charge.
If you do find yourself facing DUI charges of any kind, be sure to speak with an attorney to protect your rights. An attorney can help you examine the details of your arrest and look for the defenses you have available.
Source: Findlaw, "Georgia DUI Laws," accessed Nov. 24, 2017