What is the test for determining whether a petition has met its burden of proof?

One of the court's first remarks in ruling was that it believed "the People have met their burden." The court repeated this statement immediately before finding the petition true. "Evidence Code section 664 provides that '[it] is presumed that official duty has been regularly performed.' . . . [A] number of criminal cases unequivocally hold that th[is] rule encompasses a presumption that the trial court applied the proper burden of proof in matters tried to the court." (Ross v. Superior Court of Sacramento County (1977) 19 Cal.3d 899, 913-914.)