Driving Under the Influence is defined as operating a motor vehicle while impaired by alcohol, other drugs or intoxicating compounds. In Illinois, a driver is legally considered to be under the influence if he/she has a blood-alcohol concentration (BAC) of .08 percent or greater, has used any illegal substance, or is impaired by medication. A driver's BAC is based on the ratio of alcohol to blood or breath. However, an individual showing alcohol levels between .05 and .08 percent may be convicted of DUI if additional evidence determines that the driver was impaired. 

Penalties for DUI in Illinois vary depending upon the circumstances of the arrest and conviction, including age of the driver, driver's BAC level, whether children were being transported and whether the driver had previous DUI convictions. 

• First conviction (under age 21) — Class A misdemeanor with possible 0-12 months imprisonment; loss of driving privileges for minimum 2 years; 100 hours community service; fines of up to $2,500; eligible for Restricted Driving Permit (RDP) after one year of revocation; may be required to have a BAIID installed in vehicle as part of driving relief.

• First conviction (over age 21) — Class A misdemeanor with possible 0-12 months imprisonment; loss of driving privileges for minimum 1 year; 100 hours community service; fines of up to $2,500; eligible for RDP; may be required to have a BAIID installed in vehicle as part of driving relief.

Fines and punishments increase with each subsequent conviction.