The legal limit in Illinois for a Driving Under the Influence (DUI) charge is .08%. (625 ILCS 5/11-501) This is known as the Blood Alcohol Level or BAL.
It is a measurement of the amount of alcohol in the driver’s bloodstream. Science shows that above a certain level, alcohol negatively affects a human being’s motor skills (reaction time, coordination and judgment) which are necessary to driving safely. The State of Illinois, and in fact all 50 states, have determined that this percentage of alcohol in a person’s bloodstream renders them unfit to operate a motor vehicle within the State of Illinois, including on private property.
Upon believing that a person may be under the influence of alcohol, the police will ask the driver to perform a series of standardized field sobriety tests (SFTS), which are physical coordination, motor skill and multiple task tests to determine a driver’s possible fitness to drive. The driver will also be asked to submit to a Preliminary Breath Test (PBT) by use of a rudimentary breath alcohol testing device.
The results of this test are not admissible in court as evidence of the actual BAL (625 ILCS 5/11-501.5) However, they can be used in assessing whether the investigating officer has probable cause to make a DUI arrest.