In such action the commission's determination of the necessity of the investigation, valuation, appraisal or services shall be conclusive evidence of such necessity, and its findings and determination of facts expressed in bills rendered pursuant to RCW 80.20.020 through 80.20.060 or in any proceedings determinative of such bills shall be prima facie evidence of such facts.
[ 1961 c 14 § 80.20.040. Prior: 1939 c 203 § 2(c); RRS § 10458-6a(c).]