In the 1980’s, the Federal government began inserting itself into DUI laws. Prior to that time, matters of traffic safety were left to each state. The Federal government strong-armed the states into accepting federal oversight by threatening to withhold highway funds for those states that did not play ball.
The first example of this intrusion into states’ rights was the 55 MPH speed limit on the Interstate. Other laws have led to a nationwide drinking age of twenty-one, to the idea of a mandatory breath test suspension (known in Illinois as a statutory summary suspension) and to uniform blood alcohol level (BAL) requirements.
As of July 2, 1997, the legal BAL limit in Illinois is .08. The legal definition of BAL is 8 grams of alcohol per 100 milliliters of blood or 8 grams of alcohol per 210 liters of breath. 625 ILCS 5/11-501.2
This means you are driving under the influence if the state can prove that at the time you were in actual physical control of a motor vehicle, you had .08 grams of alcohol within 100 milliliters of blood. In the alternative, using certain breath testing devices, your breath can allegedly be converted into a blood alcohol equivalent, the limit being .08 grams of alcohol within 210 liters of breath.
Michigan passed the .08 law with a sunset provision, meaning that unless it is extended, it will go back up to .10. If that happens, MI will lose millions in highway money.
There are two different types of DUI in Illinois. The first is proof of actual impairment (common law DUI). With that type of charge, the state must prove that alcohol reduced your ability to think and act with ordinary care .
In a common law DUI, a reading of at least .08 creates a presumption that you are under the influence. A reading of .05 or less creates a presumption that you were not under the influence. A BAC of less than .08 but greater than .05 creates no presumption in either direction. 625 ILCS 5/11-501.2
Although the .08 reading creates a presumption, that merely means that the jury will be allowed to assume, absent contrary evidence, that the driver was under the influence. However, the driver can argue that even though he was above .08, he was not under the influence.