(1) All relevant evidence shall be admissible which, in the opinion of the presiding officer, is the best evidence reasonably obtainable, having due regard for its necessity, availability, and trustworthiness. "Relevant evidence" means evidence having a tendency to make the determination of the action more or less probable than it would be without the evidence.

(2) In passing upon admissibility of evidence, the presiding officer shall give consideration to, but shall not be bound to follow, the rules of evidence governing civil proceedings, in matters not involving trial by jury, in the superior courts in the state of Washington.

(3) When objection is made to the admissibility of evidence, the evidence may be received subject to a later ruling.

(4) The presiding officer may, in his or her discretion, either with or without objection, exclude inadmissible evidence, or order cumulative evidence discontinued.

(5) Parties objecting to the introduction of evidence shall state the precise grounds of objection at the time such evidence is offered.

(6) A certified laboratory report or a copy of such shall be admissible without further authentication.