Illinois sets a per se cannabis DUI threshold under 625 ILCS 5/11-501 at 5 nanograms of delta-9 THC per milliliter of whole blood, or 10 nanograms per milliliter of other bodily substance including saliva. A driver at or above that concentration is presumed impaired regardless of actual driving behavior. The chicagoduilawyer.net network flags one critical technical issue: THC lingers in blood for days after ingestion, meaning a driver who last consumed cannabis 48 hours before a stop can still exceed the threshold. Blood draw timing, chain of custody, and laboratory methodology become central defense pressure points in every Chicago cannabis DUI file.
