70 ILCS 2605/4.31
Any person who shall be served with a subpoena to appear and testify or to produce books and papers, issued by the civil service board or by any member thereof, or by any person or persons acting under the order of the civil service board in the course of an investigation conducted under any provision of this Act, and who shall refuse or neglect to appear or testify, or to produce books and papers relevant to said investigation, as commanded in such subpoena, shall be guilty of a misdemeanor and shall, on conviction, be punished as provided in section 4.33 of this Act. The fees of witnesses for attendance and travel shall be the same as the fees of witnesses before circuit courts, and shall be paid from the appropriation for the expenses of the civil service board, and any circuit court, upon application of any such member of the civil service board, may, in its discretion, compel the attendance of witnesses, the production of books and papers, and giving of testimony before the civil service board, or before any such investigating officer by attachment, or contempt or otherwise, in the same manner as the production of evidence may be compelled before the court. Every person who, having taken an oath or made affirmation before a member of the civil service board, or officer appointed by the civil service board authorized to administer oaths, shall swear or affirm wilfully, corruptly and falsely, shall be guilty of perjury, and upon conviction shall be punished accordingly.
70 ILCS 2605/4.31