RCW 9A.48.060: Reckless burning—Defense.

In any prosecution for the crime of reckless burning in the first or second degrees, it shall be a defense if the defendant establishes by a preponderance of the evidence that:

(a) No person other than the defendant had a possessory, or pecuniary interest in the damaged or endangered property, or if other persons had such an interest, all of them consented to the defendant's conduct; and

(b) The defendant's sole intent was to destroy or damage the property for a lawful purpose.