Wash. Rev. Code § 7.04A.140
(4) In any judicial, administrative, or similar proceeding, an arbitrator or representative of an arbitration organization is not competent to testify or required to produce records as to any statement, conduct, decision, or ruling occurring during the arbitration proceeding to the same extent as a judge of a court of this state acting in a judicial capacity. This subsection does not apply:
[ 2005 c 433 s 14.]