Chicago’s DUI Enforcement and the Reliance on Breathalyzers

In Chicago, DUI enforcement is a constant priority. Whether driving through the Loop late at night or heading home on I-55, motorists face the possibility of being stopped and tested for impairment. Illinois law under 625 ILCS 5/11-501establishes strict limits: 0.08% BAC for adults, 0.04% for commercial drivers, and zero tolerance for under-21 drivers.

The tool most often used to enforce these limits is the breathalyzer. At first glance, breathalyzer results appear to be scientific fact. But the reality is more complicated. The machines are based on assumptions about human biology that don’t apply equally to everyone, and Illinois law sometimes gives more weight to those numbers than they deserve.