The law regarding Driving Under the Influence, commonly referred to as DUI is found in Section 11-501 of the Illinois Vehicle Code. The full citation is: 625 ILCS 5/11-501.
11-501 is the general provision involving DUI. There are two subsections that are the most commonly used in a DUI arrest:
(A1): being applicable when a breath test, urine sample or blood draw was performed and the person was found to have an alcohol concentration of greater than 0.08 present
(A2): is applicable when the police officer believes based upon his training and experience that you were operating a vehicle with a alcohol concentration of greater than 0.08. Here there is not proof as with a breath test, urine sample or blood draw. It is simply based on what the police officer’s opinion.
If a breath sample or other sample was provided and you were over the legal limit, you will receive both a A1 and an A2 DUI charge. If you refused to give submit to a chemical sample, then you will receive only an A2 DUI charge.
Here is a link to the full Illinois Statute: