Whenever the manner of introduction of opinion or expert testimony or testimony based on economic or statistical data is governed by requirements fixed under the provisions of WAC 298-08-360 or 298-08-370, such testimony not submitted in accordance with the relevant requirements shall not be received in evidence in the absence of a clear showing that the offering party had good cause for his failure to conform to such requirements.
Wash. Admin. Code § 298-08-390
Order, § 298-08-390, filed 1/13/70; § 39, filed 12/13/67.