Witnesses shall be examined orally unless the testimony is taken by deposition as provided in §§ 91.11-91.18 (relating to depositions) or the facts are stipulated in the manner provided in § 89.72 (relating to subjects which may be considered at conferences to expedite hearings) or in § 89.131 (relating to presentation and effect of stipulations). Pursuant to Enforcement Rule 213(e), witnesses whose testimony is to be taken shall be sworn, or shall affirm, before their testimony shall be deemed evidence in the proceeding or any questions are put to them.
204 Pa. Code § 89.121