Whether a defendant must show inability to discover favorable evidence through due diligence to establish 'suppression' under Brady v. Maryland

QUESTIONS PRESENTED 1. Whether, to establish “suppression” under Brady v. Maryland, 373 U.S. 83 (1963), and the parallel “cause” to excuse procedural default of a Brady claim, a defendant must show that he could not have discovered the favorable evidence through his own independent due diligence, as the Fifth Circuit and five other circuits have held, or whether the defendant’s diligence is irrelevant to the analysis of “suppression” and “cause,” as the remaining six courts of appeals have held. 2. Whether a petitioner may present separate and distinct causes excusing the procedural default of claims that have been found to relate back to an original federal habeas petition under Mayle v. Felix, 545 U.S. 644 (2005), or whether a petitioner is restricted to presenting a single cause excusing default where claims relate back.