Wash. Admin. Code § 480-07-495
(1) Admissibility; exclusion; offer of proof. All relevant evidence is admissible if the presiding officer believes it is the best evidence reasonably obtainable, considering its necessity, availability, and trustworthiness. The presiding officer will consider, but is not required to follow, the rules of evidence governing general civil proceedings in nonjury trials before Washington superior courts when ruling on the admissibility of evidence.
The presiding officer may exclude evidence that is irrelevant, repetitive, or inadmissible, whether or not a party objects to the evidence. Parties objecting to the introduction of evidence must state the grounds for the objection at the time the evidence is offered. If the presiding officer excludes the evidence from the record, the presiding officer may provide the party offering that evidence with the opportunity to make an oral or written offer of proof briefly describing the nature and purpose of the evidence for subsequent review of the presiding officer's ruling.
(2) Official notice.
(a) The commission may take official notice of:
(i) Any judicially cognizable fact, examples of which include, but are not limited to, the following:
[Statutory Authority: RCW 80.01.040 and 80.04.160. WSR 17-06-051 (General Order R-588), § 480-07-495, filed 2/28/17, effective 3/31/17; WSR 03-24-028 (General Order R-510, Docket No. A-010648), § 480-07-495, filed 11/24/03, effective 1/1/04.]