A certificate of probable cause (CPC) is generally issued to indicate that an attempt to bring an appeal is not frivolous. CPCs are governed by federal and state laws, which vary by jurisdiction. For example, in one state, a defendant may not appeal from a judgment of conviction following a guilty or no contest plea, unless he files with the trial court a written, sworn statement “showing reasonable, constitutional, jurisdictional, or other grounds going to the legality of the proceedings,” and the trial court executes and files “a certificate of probable cause for such appeal with the county clerk. It attempts to determine whether the appeal is clearly frivolous and vexatious or whether it involves an honest difference of opinion.
A federal law required a petitioner in state custody to obtain a CPC to establish federal appellate court jurisdiction over an appeal of the district court’s denial of a habeas corpus petition. A CPC required a showing of more than good faith or an absence of frivolity.
In Barefoot v. Estelle, 463 U.S. 880 (1983), the Supreme Court held that a CPC requires a “substantial showing of the denial of a federal right.” In a capital case, the nature of the death penalty is a proper subject of consideration in determining whether to issue a certificate, but the “severity of the penalty does not in itself suffice to warrant the automatic issuing of a certificate.” A substantial showing of the denial of a federal right does not require a showing that the petitioner would prevail on the merits. Rather, the Court held that petitioner must demonstrate one of the following: (1) the issue presented is “debatable among jurists of reason,” (2) a court could resolve the issue in a different manner, or (3) the issue deserves further proceedings.
In 1996, a federal law was enacted to require a “certificate of appealability” (COA) for both certain cases. Circuit courts may grant a COA only upon a “substantial showing of the denial of a constitutional [not a federal] right.” Also in contrast to the former CPC protocol, AEDPA requires a COA to be issued on a claim specific basis.