Ill. Admin. Code tit. 35, § 168.270 – Rules of Evidence

a) Irrelevant, immaterial or unduly repetitious evidence shall be excluded. The rules of evidence and privilege as applied in civil cases in the circuit courts of Illinois shall be followed. However, evidence not admissible under such rules of evidence may be admitted, except where precluded by statute, if it is of a type commonly relied upon by reasonably prudent persons in the conduct of their affairs.
b) Objections to evidentiary offers may be made and shall be noted in the record.
c) When a Hearing is expedited and the interests of the parties will not be prejudiced, any part of the evidence may be received in written form.