Does a defendant have a claim that his conviction for sexual assault against him be quashed on appeal?

Defendant also contends that his conviction violates due process. This claim was not included in defendant's federal habeas petition. ⁵ Because "[h]abeas claims that are not raised before the district court in the petition are not cognizable on appeal," Cacoperdo v. Demosthenes, 37 F.3d 504, 507 (9th Cir.1994), we do not review the merits of defendant's due process claim. See Willard v. California, 812 F.2d 461, 465 (9th Cir.1987) ("We do not entertain [defendant's habeas] claim because [he] did not include it in his petition to the district court, and the district court did not address it.").

Moreover, reaching the merits of defendant's claim in this instance would require not only that we ignore defendant's failure to raise the claim in his petition, but also that we raise and decide threshold procedural issues. Because defendant's due process claim was not raised in any state proceeding, questions of exhaustion and procedural default are clearly implicated. See Duncan v. Henry, --- U.S. ----, ----, 115 S.Ct. 887, 888 (1995) (per curiam) ("If a habeas petitioner wishes to claim that ... a state trial court denied him the due process of law guaranteed by the Fourteenth Amendment, he must say so, not only in federal court, but in state court."). Those questions are best left to the court in which the due process claim has been properly raised.