(1) Subject to the other provisions of these rules, all relevant evidence is admissible which, in the opinion of the presiding officer, is the best evidence reasonably obtainable, having due regard for its necessity, availability and trustworthiness.

(2) If not allowing evidence to be admitted, the presiding officer must give consideration to, but is not bound to follow, the rules of evidence governing civil proceedings, in matters not involving trial by jury in the superior courts of the state of Washington.