RCW 11.24.030: Burden of proof.

In any such contest proceedings the previous order of the court probating, or refusing to probate, such will shall be prima facie evidence of the legality of such will, if probated, or its illegality, if rejected, and the burden of proving the illegality of such will, if probated, or the legality of such will, if rejected by the court, shall rest upon the person contesting such probation or rejection of the will.