30 ILCS 5/3-13
The Auditor General, or any person designated by him for that purpose, may administer oaths or affirmations and take the deposition or testimony of any person.
Subpoenas to compel the attendance of witnesses or the production of books, records, work papers or other documentation may be issued by the Auditor General in connection with any post audit or investigation authorized by or under this Act. Subpoenas must be signed personally by the Auditor General or by a Deputy Auditor General, and must pertain to information properly within the scope of the post audit or investigation.
If any person fails to obey a subpoena issued under this Section, the Auditor General may apply to any circuit court to secure compliance with the subpoena. The failure to comply with the order of the court issued in response thereto shall be punished as a contempt.
30 ILCS 5/3-13