(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:

(A) Rules, regulations, interpretive and policy statements, administrative rulings, and orders, exclusive of findings of fact, of the commission and other governmental agencies;

(B) Contents of certificates, permits, and licenses issued by the commission; and

(C) Tariffs, classifications, and schedules regularly established by, or filed with, the commission as required or authorized by law;

(ii) Technical or scientific facts within the commission's specialized knowledge;

(iii) Codes or standards that have been adopted by an agency of the United States or a state, or by a nationally recognized organization or association; and

(iv) Records contained in government websites or publications or in nationally recognized reporting service publications that are in general circulation and readily accessible to all parties.

(b) The commission may, in its discretion upon notice to all parties, inspect physical conditions that are at issue and take official notice of the results of its inspection.

(c) The presiding officer will notify parties of documents or information of which the commission takes official notice and the source of that information. The presiding officer will afford parties an opportunity to contest facts and material of which the commission takes official notice. The presiding officer may require a party proposing that the commission take official notice of a document or information to provide copies of that document or information for the record and to all other parties.