Wash. Rev. Code § 36.01.060
Each county shall be liable to pay the per diem and mileage, or other compensation in lieu thereof, to jurors of the county attending the superior court; the fees of the sheriff for maintaining prisoners charged with crimes, and the sheriff's costs in conveying them to and from the court, as well as their board while there; the per diem and mileage, or such other compensation as is allowed in lieu thereof, of the sheriff of the county, when in criminal cases the sheriff is required to attend or travel to the superior court out of the limits of the sheriff's county; the costs in criminal cases taken from the courts of limited jurisdiction to the superior court; but no such claims shall be paid by the treasurer unless the particular items are approved by the judge and certified by the clerk under the seal of the court. For the time or travel which may be paid by the parties or United States, no payment from the county shall be allowed, and no officer, juror, or witness shall receive from the county double pay as a per diem for the same time, or as traveling expenses or mileage for the same travel, in however many different capacities or in however many different causes they may be summoned, notified, or called upon to testify or attend in.
RCW 36.01.060
Intent-1987 c 202: See note following RCW 2.04.190.