The following cases highlight that a convicted felon has the burden of demonstrating to the trial court's satisfaction the high standards of rehabilitation have been met. Many petitioners who are eligible to petition still may not receive a certificate of rehabilitation. For example, in People v. Ansell (2001) 25 Cal.4th 868, the California Supreme Court recognized there was a lack of published cases interpreting the statutory scheme. It summarized the relevant legislative history and considered whether the 1997 amendment to section 4852.01, which excluded persons convicted of certain specified sex offenses from petitioning for a certificate, violated the prohibition against ex post facto laws under the federal and state constitutions ( 4852.01, subd. (d)). The court concluded the amendment could be applied to deny a certificate of rehabilitation to a person who had committed sex offenses prior to its enactment without violating the ex post facto prohibition. It explained the disabilities from which a certificate can release a convicted felon are civil and "serve vital public interests," and they do not involve punishment for the underlying crime. (Ansell, supra, 25 Cal.4th at pp. 888-889.) In other words, the certificate of rehabilitation does not involve an additional criminal prosecution or punishment. Additionally, the Supreme Court rejected defendant's "suggestion that absent section 4852.01, subdivision (d), a certificate of rehabilitation is necessarily available to any convicted felon who claims to meet the minimum statutory requirements and is otherwise eligible to apply. As we have explained, the superior court conducts a thorough inquiry into the applicant's conduct and character from the time of the underlying crimes through the time of the certificate of rehabilitation proceeding. . The standards for determining whether rehabilitation has occurred are high. . The decision whether to grant relief based on the evidence is discretionary in nature. Citation; see 4852.13, subd. (a), as amended by Stats. 1996, ch. 129, 2, eff. July 8, 1996 clarifying that a certificate of rehabilitation 'may' issue upon the requisite showing of reform.)" (Ansell, supra, 25 Cal.4th at p. 887.) The court recognized the certificate of rehabilitation "also serves as a judicial recommendation for a pardon." (Id. at p. 891.)