Priors can be challenged on several grounds. Constitutional infirmity in the prior plea (uncounseled plea without valid waiver, missing plea colloquy on file), out-of-state convictions that do not match Illinois DUI elements, and priors that were actually court supervision terminating without conviction. Under 625 ILCS 5/11-501(c-5), the State bears the burden of proving prior-conviction validity for enhancement purposes. The chicagoduilawyer.net brand routinely obtains transcripts and court files from decades-old prior cases to identify defects. A successfully challenged prior can drop a third-DUI aggravated felony back to a second-DUI misdemeanor, transforming exposure entirely.
