Wash. Rev. Code § 48.18.450
Life insurance may be made payable to a trustee to be named as beneficiary in the policy and the proceeds of such insurance paid to such trustee shall be held and disposed of by the trustee as provided in a trust agreement or declaration of trust made by the insured during his or her lifetime. It shall not be necessary to the validity of any such trust agreement or declaration of trust that it have a trust corpus other than the right of the trustee to receive such insurance proceeds as beneficiary, and any such trustee may also receive assets, other than insurance proceeds, by testamentary disposition and administer them according to the terms of the trust agreement or declaration of trust as they exist at the death of the testator.
RCW 48.18.450