I'm sure the Zahaus didn't file a WDS for retaliation purposes. That would make it technically frivolous.
I get what your saying though. A trial might help clear suspicions (for all involved). But I have little faith anybody would change their mind no matter how much evidence is shown. I've seen it in other cases. People confirm the evidence that supports their opinion and discount the evidence that does not.
Personally, if my loved ones still had faith and love for me, I'm not sure how motivated I would be to "clear my name".
BBM: Being accused of murdering a child is a legacy the whole family would live with, IMO.
I don't think that is the only reason for the WDS, it just added to the unanswered and unchallenged.