An underutilized, yet powerful tool in news reporting is the Illinois Freedom of Information Act (FOIA)
Under FOIA, records in the possession of public agencies may be accessed by the public upon written request. Public Records include all records, reports, forms, writings, letters, memoranda, books, papers, maps, photographs, cards, tapes, recordings, electronic data processing records, recorded information, and all other documentary materials, regardless of physical form or characteristics, having been prepared or having been or being used, received, in the possession of or under the control of any public body.
The public body must respond to your FOIA request within five business days after receiving the request. The request recipient may extend that time period an additional five working days under certain conditions. If additional time is needed the agency must notify you in writing within five business days to explain why the delay is needed and when the information will be provided. The Illinois Attorney General provides an excellent summary of the rules of the timeline and extensions. The agency can potentially face fines and penalties for violating the law. You can make make a written agreement with the body to extend the deadline to respond.
That same link also provides information on the limited fees which can be charged for the information and other options a requester has in lieu of paying the charges. It also covers actions you may take if denied the information requested.