820 ILCS 40/4

Personnel record information which was not included in the personnel record but should have been as required by this Act shall not be used by an employer in a judicial or quasi-judicial proceeding. However, personnel record information which, in the opinion of the judge in a judicial proceeding or the hearing officer in a quasi-judicial proceeding, was not intentionally excluded from the personnel record may be used by the employer in the proceeding if the employee agrees or has been given a reasonable time to review the information. Material which should have been included in the personnel record shall be used at the request of the employee.