(A) The purpose of rules 4901-1-16 to 4901-1-24 of the Administrative Code is to encourage the prompt and expeditious use of prehearing discovery in order to facilitate thorough and adequate preparation for participation in commission proceedings. These rules are also intended to minimize commission intervention in the discovery process.
(B) Except as otherwise provided in paragraphs (G) and (I) of this rule, any party to a commission proceeding may obtain discovery of any matter, not privileged, which is relevant to the subject matter of the proceeding. It is not a ground for objection that the information sought would be inadmissible at the hearing, if the information sought appears reasonably calculated to lead to the discovery of admissible evidence. Discovery may be obtained through interrogatories, requests for the production of documents and things or permission to enter upon land or other property, depositions, and requests for admission. The frequency of using these discovery methods is not limited unless the commission orders otherwise under rule 4901-1-24 of the Administrative Code.
(C) Any party may, through interrogatories, require any other party to identify each expert witness expected to testify at the hearing and to state the subject matter on which the expert is expected to testify. Thereafter, any party may discover from the expert or other party facts or data known or opinions held by the expert which are relevant to the stated subject matter. A party who has retained or specially employed an expert may, with the approval of the commission, require the party conducting discovery to pay the expert a reasonable fee for the time spent responding to discovery requests.
(D) Discovery responses which are complete when made need not be supplemented with subsequently acquired information except in the following situations:
(1) The response identified each expert witness expected to testify at the hearing or stated the subject matter upon which each expert was expected to testify.
(2) The responding party later learned that the response was incorrect or otherwise materially deficient.
(3) The response indicated that the information sought was unknown or nonexistent and such information subsequently became known or existent.
(4) An order of the commission or agreement of the parties provides for the supplementation of responses.
(5) Requests for the supplementation of responses are submitted prior to the commencement of the hearing.
(6) The response addressed the identity and location of persons having knowledge of discoverable matters.
(E) The supplementation of responses required under paragraphs (D)(1) to (D)(3) and (D)(6) of this rule shall be provided within five business days of discovery of the new information.
(G) A discovery request under rules 4901-1-19 to 4901-1-22 of the Administrative Code may not seek information from any party which is available in prefiled testimony, prehearing data submissions, or other documents which that party has filed with the commission in the pending proceeding. Before serving any discovery request, a party must first make a reasonable effort to determine whether the information sought is available from such sources.
(H) For purposes of rules 4901-1-16 to 4901-1-24 of the Administrative Code, the term"party" includes any person who has filed a motion to intervene which is pending at the time a discovery request or motion is to be served or filed.