This Court has never squarely held that the Compulsory Process Clause guarantees the right to discover the identity of witnesses, or to require the government to produce exculpatory evidence. But cf. United States v. Nixon,
418 U.S. 683, 709 , 711 (1974) (suggesting that the Clause may require the production of evidence). Instead, the Court traditionally has evaluated claims such as those raised by Ritchie under the broader protections of the Due Process Clause of the Fourteenth Amendment. See United States v. Bagley,
473 U.S. 667 (1985); Brady v. Maryland,
373 U.S. 83 (1963). See also Wardius v. Oregon,
412 U.S. 470 (1973). Because the applicability of the Sixth Amendment to this type of case is unsettled, and because our Fourteenth Amendment precedents addressing the fundamental fairness of trials establish a clear framework for review, we adopt a due process analysis for purposes of this case. Although we conclude that compulsory process provides no greater protections in this area than those afforded by due process, we need not decide today whether and how the guarantees of the Compulsory Process Clause differ from those of the Fourteenth Amendment. It is enough to conclude that on these facts, Ritchie's claims more properly are considered by reference to due process.
[480 U.S. 39, 57]
It is well settled that the government has the obligation to turn over evidence in its possession that is both favorable to the accused and material to guilt or punishment. United States v. Agurs,
427 U.S. 97 (1976); Brady v. Maryland, supra, at 87. Although courts have used different terminologies to define "materiality," a majority of this Court has agreed, "[e]vidence is material only if there is a reasonable probability that, had the evidence been disclosed to the defense, the result of the proceeding would have been different. A `reasonable probability' is a probability sufficient to undermine confidence in the outcome." United States v. Bagley,
473 U.S., at 682 (opinion of BLACKMUN, J.); see id., at 685 (opinion of WHITE, J.).