What is the burden of proof at appeal when a plaintiff fails to prove their case by a preponderance?

Shoen first argues that respondents failed to prove their case by clear and convincing evidence. "That standard was adopted, however, for the edification and guidance of the trial court, and was not intended as a standard for appellate review." (Crail v. Blakely (1973) 8 Cal.3d 744, 750.) Thus, "to the extent [Shoen] means to say we must find more substantial evidence to support the trial court's finding . . . than we would if the burden of proof had been only a preponderance of the evidence, he is mistaken. Our review is the same regardless of the burden of proof at trial." (In re Marriage of Murray (2002) 101 Cal.App.4th 581, 604.) As explained above, if substantial evidence exists to support the trial court's conclusions, they are not open to review on appeal. (Applegate, supra, 146 Cal.App.3d at p. 708.)