Generally, a justification defense will not be successful, but it is technically possible.
In a justification defense, the accused must first admit that they violated the law; however, the violation of the law should be excused because there was a justifiable and compelling reason.
You cannot have it both ways, where a person says I did not commit the crime; however if you think that I did, there was an excusable reason.
An example of a justification defense is where a person is defending him or herself. Self Defense is the classic example of justification. In a self-defense situation, there is no question that the accused caused bodily harm to another person. The defense is that the accused had a right to protect him or herself from the other person, and as a result, caused that person bodily harm.
The problem with justification, as a defense to a DUI in Georgia, is that very few things can justify drunk driving.
One possibility is where a person is fleeing a domestic violence situation and must leave to save him or herself from immediate bodily harm. The practical problem is that once the person is safely away, they must then stop their vehicle and call for help.
Once out of danger, the risk to the public exceeds the risk to the person fleeing. As a result, if they do not stop their car and call the police, their actions are no longer justified.
In my experience, victims of domestic violence do not follow the above-stated course of conduct. More often, they try to drive to a friend or family member's home. As the point, they are no longer in danger; they would not be justified in their continued driving. This is why justification, as a defense to a Georgia DUI case, very often is unsuccessful.