What is the test for establishing a waiver of child support?

In addition to establishing facts constituting extrinsic fraud or mistake, father must demonstrate probable error in the final judgments from which he seeks relief. He must show, in other words, "facts indicating a sufficiently meritorious claim to entitle [him] to a fair adversary hearing." (In re Marriage of Park, supra, 27 Cal.3d 337, 346, 165 Cal.Rptr. 792, 612 P.2d 882; see also Bennett v. Hibernia Bank (1956) 47 Cal.2d 540, 554, 305 P.2d 20.) I agree with the majority that father's allegations of mother's active concealment, making it practically impossible for father to pay the child support installments as they fell due, are relevant to establish a defense of estoppel or waiver. ³ Again, however,

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