Legal Question in Civil Litigation in Washington

Well, there is nothing to say that they can't try, but you have a solid defense if they do, which is to assert the equitable defenses of collateral estoppel and res judicata which are related. In short, both the claims against you and the issues arising out of those claims were already litigated, and therefore, as a matter of fairness, the plaintiff is estopped (precluded) from re-litigating them in a separate trial.

There is a very good reason for these rules, which is to ensure that plaintiffs bring all their causes of action against all known defendants at one time, so that courts aren't clogged with hundreds of lawsuits arising out of the same set of facts or transactions. (Think of class action lawsuits and you can see how those save tons of court time.)

In any case, from your facts, I am not sure if the claim for the money was made at trial and denied, or if it was never brought up, but depending on which of those is true, that will help you decide whether to assert res judicata (claim preclusion) from the latin, meaning that something has been adjudicated already, or collateral estoppel (issue preclusion). Frankly, it's a little sloppy, but you can assert both if you are not sure which applies.

Ultimately, I suggest that you consult an attorney to be sure of what you're doing and to ensure that you properly assert your defenses to the new lawsuit.