(a) If copies of the documentary evidence which the department plans to use at the hearing have not been provided to the appellant, or the appellant's representative, an opportunity to examine such documents, if requested, must be afforded the appellant at the prehearing conference.

(b) The appellant must be afforded an opportunity to examine the audit file at the prehearing conference and to make copies of any relevant documents contained in the file without charge. However, information relating to the selection of the person for audit, investigation notes or other material which may reveal investigation techniques, material prepared for submission to a law enforcement or prosecutorial agency, information concerning law enforcement investigations, or judicial proceedings or confidential sources or confidential information need not be revealed.