According to the Mayo Clinic, blood alcohol concentration is the amount of alcohol in the bloodstream expressed as a percentage. In Illinois, as in all 50 states, having a BAC of at least 0.08% equates to legal intoxication. This would mean that a person has eight parts of ethyl alcohol or ethanol for every 1,000 parts of blood. 

Knowing the laws about driving while intoxicated may help someone plan a defense — or avoid the arrest in the first place. 

Blood alcohol concentration

Many factors play into a person’s BAC. Even a healthy 180-pound man could reach the legal limit of 0.08% from two craft beers after work. But BAC is not the same for everyone. Women typically metabolize alcohol more slowly and are therefore more susceptible. Weight and body composition are significant factors, as is how much of an alcohol tolerance someone has built up over time. 

State law in Illinois dictates that driving while legally intoxicated can result in fines of thousands of dollars, community service and jail time for even a first offense. Multiple offenses can add up to a felony and result in significant jail time, large fines and the loss of a license. 

Traffic stops

If an officer asks a driver to take a BAC test, refusing to comply in Illinois will automatically result in a license suspension for one year — three years if it is the second time refusing a test at a traffic stop. 

But a driver can test zero on a BAC test and still receive a DUI in Illinois. State law gives the ability to charge a driver even with a BAC under the limit. If the driver has been mixing alcohol with prescription drugs — even those he or she takes legally — an officer may claim that the driver’s ability to handle the vehicle is significantly impaired. Any detectable amount of illegal drugs can result in a charge, as well. 

If the officer determines that the driver is extremely impaired, he or she may make a charge of “aggravated  driving under  the  influence.” For this, sentencing minimums increase significantly.