Evidence shall be admitted in accordance with this chapter and State Government Article, §10-213, Annotated Code of Maryland. Evidence may not be excluded solely on the grounds that it is hearsay. Exclusion of Witnesses. Upon request by a party, the Secretary or the Commission, as appropriate, may exclude witnesses other than parties from the hearing room. The Secretary or the Commission, as appropriate, may order the witnesses, parties, attorneys, and all others present in the hearing room not to disclose to any witness excluded under this section the nature, substance, or purpose of testimony, exhibits, or other evidence introduced during the witness' absence. A party that is not an individual may designate an individual to remain in the hearing room, even though the individual may be a witness. An expert witness who is to render an opinion based on testimony given at the hearing may remain during the testimony. Prefiled Testimony. In the discretion of the Secretary or the Commission, as appropriate, testimony may be received in written form. The testimony shall be filed with the Secretary or the Commission, as appropriate, and served on opposing parties so that it is received at least 5 days before the hearing.