89 Ill. Adm. Code 270.448
Expert Testimony
Section 270.448 Expert Testimony
a) If
scientific, technical, or other specialized knowledge will assist the ALJ to
understand the evidence or to determine a fact in issue, a witness qualified as
an expert by knowledge, skill, experience, training or education may testify
and render an opinion.
b) The
party seeking to introduce expert testimony bears the burden of establishing
the witness' expertise. The ALJ determines whether the witness is sufficiently
qualified as an expert.
c) The
expert may only testify as to matters within his or her area of expertise.
d) An
expert may give an opinion on the ultimate issue in the proceeding.
e) The
facts or data upon which an expert bases an opinion may be those perceived by
or made known to the expert at or before the hearing. The facts or data need
not be admissible in evidence if they are of a type reasonably relied upon by
experts in the particular field in forming opinions upon the subject.