10 ILCS 5/29-9: Unlawful observation of voting.

Except as permitted by this Code, any person who knowingly marks his ballot or casts his vote on a voting machine or voting device so that it can be observed by another person, and any person who knowingly observes another person lawfully marking a ballot or lawfully casting his vote on a voting machine or voting device, shall be guilty of a Class 4 felony.