RCW 11.84.080: Contingent remainders and future interests.

As to any contingent remainder or executory or other future interest held by the slayer or abuser, subject to become vested in him or her or increased in any way for him or her upon the condition of the death of the decedent:

(1) If the interest would not have become vested or increased if he or she had predeceased the decedent, he or she shall be deemed to have so predeceased the decedent;

(2) In any case the interest shall not be vested or increased during the period of the life expectancy of the decedent.