Intrusion law in Illinois does not differ in any significant way from the law described in the General Elements of an Intrusion Claim section of this guide. See Burns v. Masterbrand Cabinets, Inc., 874 N.E.2d 72, 75-77 (Ill. Ct. App. 2007). As result, you should follow the general advice outlined in the section on Practical Tips for Avoiding Liability When Gathering Private Information.
Illinois courts do, however, differ slightly in describing the second element of a claim, requiring that the intrusion must be "offensive or objectionable." It does not appear that this change materially affects the outcome of cases.
The Seventh Circuit Court of Appeals, which covers federal courts in Illinois, has hinted that there may be a First Amendment privilege to intrude with respect to matters of public concern. See Desnick v. American Broadcasting Co., 44 F.3d 1345 (7th Cir. 1995). Using this logic, a federal district court judge stated that if the media could show that their intrusive activities were necessary to expose improper prison conditions, a highly newsworthy and publicly concerned topic, that could be a possible defense to intrusion. See Huskey v. NBC, 632 F.Supp. 1282, 1291 (N.D. Ill. 1986).