In the case of Philip Parker, Warden v. David Eugene Matthews in 2011, the US Supreme Court was asked to consider whether a state court's decision that evidence was not material under Brady v. Maryland could be considered an unreasonable application of clearly established federal law. The petitioner, David Eugene Matthews had been convicted for murder and burglary in Kentucky state courts and sentenced to death. He claimed that his rights were violated because prosecutors did not disclose certain exculpatory evidence during his trial as required by Brady v. Maryland (1963). However, both the District Court and Sixth Circuit ruled against him stating that he failed to establish any violation under Brady since he couldn't prove "materiality" - i.e., there wasn't a reasonable probability that if the jury heard this undisclosed evidence it would have changed their verdicts on guilt or punishment phases of his trial. The Supreme Court reversed these decisions ruling in favor of Matthews by holding that when assessing materiality for purposes of Brady analysis: firstly one must consider all suppressed evidences collectively rather than individually; secondly one should assume they would have been effective at trial; thirdly even if enough other incriminating evidence exists such suppression can still be prejudicial.

In the dissenting opinion for Philip Parker, Warden v. David Eugene Matthews, Justice Scalia argued that the majority's decision to grant habeas relief was incorrect because it failed to adhere to the Antiterrorism and Effective Death Penalty Act of 1996 (AEDPA). He contended that under AEDPA, federal courts should not overturn a state court's decision unless it is contrary or an unreasonable application of clearly established Federal law. According to him, Kentucky Supreme Court’s ruling did not contradict any U.S. Supreme Court precedent nor was its conclusion based on an unreasonable determination of facts in light of evidence presented during trial. Furthermore, he criticized the majority for basing their judgment on what they believed were "better" legal principles rather than adhering strictly to existing precedents and statutory requirements set by Congress.