In the case of Harris v. Reed, Warden et al., 1988, the U.S. Supreme Court ruled that a state appellate court must clearly indicate its reliance on procedural default to bar federal habeas review. The petitioner, Harris was convicted of murder and sentenced to death in Illinois state court. His conviction was affirmed by the Illinois Supreme Court which rejected his claim that he had been denied effective assistance of counsel during sentencing proceedings due to an alleged conflict of interest involving his lawyer's prior representation of a prosecution witness. When Harris sought federal habeas corpus relief based on this same claim, it was dismissed as procedurally barred because he hadn't raised it at trial or in post-trial motions as required under Illinois law. The U.S Supreme Court reversed this decision stating that if a state court does not explicitly rely on procedural default when dismissing claims but instead addresses them on their merits then those claims are not procedurally defaulted for purposes of federal habeas review. This ruling established what is known as "the Harris presumption" - unless there is clear indication from the record that a state-court decision rests upon adequate and independent grounds (such as procedural default), it will be presumed that any unexplained denial rested upon federal law – thus allowing for potential further appeal within Federal courts.

In the dissenting opinion for Harris v. Reed, Justice Scalia argued that the majority's decision to apply a presumption of prejudice in favor of habeas corpus petitioners was not supported by precedent or statute. He contended that this approach would encourage federal courts to second-guess state court decisions and undermine their authority. Furthermore, he expressed concern about the potential impact on judicial resources, as it could lead to an increase in frivolous appeals from prisoners seeking relief under habeas corpus provisions. In his view, if a state court's reasoning is unclear but can be reasonably interpreted as resting on independent and adequate state grounds, then federal review should be barred.