Appellant’s Brady claim was preserved where the federal court erred in finding that the claim had previously been rejected by the state courts. The Tennessee Supreme court affirmed Cone’s conviction and death sentence, and the state courts denied post-conviction relief. In a second habeas petition, Cone raised the claim that the State had violated Brady v. Maryland by suppressing witness reports that would have corroborated his insanity defense and mitigated the penalty. Cone was denied a hearing based on the ground that the Brady claim had been previously determined, and the appellate court affirmed. Cone petitioned for relief in federal court, which denied relief, finding the Brady claim procedurally barred. It also held that even if he had not defaulted the claim, it would fail on its merits because none of the withheld evidence would have cast doubt on his guilt. The Sixth Circuit agreed, but considered itself barred from reaching the claim’s merits because the state courts had ruled the claim previously determined or waived under state law. The United States Supreme Court reversed and remanded. The state courts’ rejection of the Brady claim did not rest on a ground that barred federal review. The Sixth Circuit’s rejection of the claim as procedurally defaulted was therefore erroneous. The lower federal courts failed to adequately consider whether the withheld documents were material to Cone’s sentence. The evidence did not support his insanity defense, however, so the Sixth Circuit did not err by denying habeas relief on the ground that such evidence was immaterial to the jury’s guilt finding. However, the same cannot be said of whether the evidence would have influenced the jury’s sentencing recommendation. Because the suppressed evidence might have been material to the jury’s assessment of the proper punishment, a full review is warranted.