The Illinois 20-minute observation period is a foundational rule under 20 Ill. Adm. Code 1286. Before an evidentiary breath test, a certified operator must continuously observe the subject for at least 20 minutes to confirm no ingestion, regurgitation, burping, vomiting, smoking, or foreign material in the mouth occurs. The purpose is to prevent residual mouth alcohol from producing a falsely elevated reading. Interruption of observation, distraction, absence, or failure to reset after a burp all break the period. Body cam and station video are compared against the operator's testimony. A Chicago DUI lawyer treats any documented lapse as a suppression basis under Illinois evidentiary rules.
