Wash. Rev. Code § 26.14.240
(4) An arbitrator is not competent to testify, and may not be required to produce records, in a judicial, administrative, or similar proceeding about a statement, conduct, decision, or ruling occurring during an arbitration, to the same extent as a judge of a court of this state acting in a judicial capacity. This subsection does not apply:
[ 2023 c 61 s 25.]