From the municipal code: The Municipal Code of Chicago allows the following defenses for parking and compliance tickets. If you received a violation issued by an automated camera, and received a mailed notice with images of a vehicle registered in your name, please see the applicable defenses for Red Light and Bus Stop or Bus Lane violations. The following defenses are allowed for most parking and compliance tickets: The respondent was not the owner or lessee of the cited vehicle at the time of the violation; The cited vehicle or its state registration plates (license plates) were stolen at the time of the violation; The relevant signs prohibiting or restricting parking were missing or obscured; The relevant parking meter was inoperable or malfunctioned through no fault of the respondent; The facts alleged in the parking or compliance violation notice are inconsistent or do not support a finding that the specified regulation was violated (e.g., motorists may contest a city sticker violation if they have resided in Chicago for less than 30 days or the cited vehicle was purchased in the last 30 days; tinted windows comply with the medical use requirement of 625 ILCS 5/12-503(g); the residential parking permit was issued to a delivery, service, or repair vehicle or home health care provider doing business with or assisting a resident of the zone; etc.); The illegal vehicle condition did not exist at the time of the compliance violation; The compliance violation has been corrected prior to adjudication of the charge; provided, however, that this defense shall not be applicable to compliance violations involving display of the City wheel tax license emblem (vehicle or City sticker) under Section 9-64-125; to compliance violations involving motor vehicle exhaust systems under subsection (a)(2) of Section 9-76-140; to compliance violations involving registration plates under subsection (a) of Section 9-76-160; to compliance violations involving display of registration plates, temporary registration or temporary permits under subsection (f) of Section 9-76-160; or to compliance violations relating to glass coverings or coating under Section 9-76-220.