Procedural Bar. If a petitioner has failed to present a particular claim before a state court in the manner prescribed by the state's procedural rules, a federal court will generally refuse to consider that claim on habeas review. A petitioner can overcome the procedural bar only by demonstrating either (1) cause for the procedural default and actual prejudice as a result of the alleged violation of federal law, or (2) that failure to review the claims will “result in a fundamental miscarriage of justice.” To demonstrate a fundamental miscarriage of justice, a habeas petitioner may present new reliable evidence supporting a claim of actual innocence, but the petitioner “must show that it is more likely than not that no reasonable juror would have convicted him in the light of the new evidence.” A petitioner can satisfy the “cause” requirement by showing, for example, that assistance of counsel was ineffective in violation of the Sixth Amendment, or that governmental interference rendered procedural compliance impracticable. A petitioner's illiteracy, pro se status, lack of legal knowledge, or reliance upon other inmates' assistance in preparing claims generally does not constitute sufficient cause to excuse a procedural default. To establish prejudice, a petitioner must show “not merely that the errors at his trial created a possibility of prejudice, but that they worked to his actual and substantial disadvantage, infecting his entire trial with error of constitutional dimensions.”

Federal courts considering a habeas claim should determine whether the claim is procedurally barred before considering whether relief is precluded by Teague's rule against applying “new” rules of constitutional law. If the last state court to which a federal claim is presented ignores a potential state procedural default and reaches the merits of the claim, federal courts may consider the claim. If the last state court opinion is ambiguous as to whether it reached merits of claim or rendered its decision on procedural grounds, a federal court will presume state court reached the merits based on the last related state-court decision. However, this presumption is overcome if a state court invokes a state procedural bar that provides adequate grounds for dismissal independent of federal law, or if the last state order or opinion summarily upholds a reasoned lower state court decision that invokes a state procedural bar.