(a) Legal rules of evidence shall not be in effect at administrative hearings. However, only evidence relevant to issues within the scope of review under § 68.8 shall be admissible.

(b) Documentary and oral evidence shall be admissible.

(c) Admissibility of non-expert testimony shall be within the discretion of the board.

(d) All testimony shall be under oath.

(e) Res judicata/collateral estoppel. Where there has been a previous determination, decision or finding of fact by the Director, one of his delegees, an administrative law judge, hearing officer, or hearing board regarding the base flood elevations of any other community, such determination, decision, or finding of fact shall not be binding on the board and may only be admissible into evidence if relevant.