Legal Question in Family Law in Washington

In the state of Washington, adultery has no legal relevance in a divorce, the only available cause for divorce is that "the marriage is irretrievably broken," (Washington is a no fault divorce state). I generally recommend that parties not begin a new relationship until the current one is completely resolved as it may contribute to emotional conflicts and stress that causes parties to fight over things of little consequence, but there is no legal issue.

http://www.itforensics.com/our_staff/chris_steuart.htm