527 U.S. 263 (1999)

STRICKLER
v.
GREENE, WARDEN

No. 98-5864.

United States Supreme Court.

Argued March 3, 1999. Decided June 17, 1999. CERTIORARI TO THE UNITED STATES COURT OF APPEALS FOR THE FOURTH CIRCUIT

*264 *265 Stevens, J., delivered the opinion of the Court, in which Rehnquist, C. J., and O'Connor, Scalia, Ginsburg, and Breyer, JJ., joined in full, in which Kennedy and Souter, JJ., joined as to Part III, and in which Thomas, J., joined as to Parts I and IV. Souter, J., filed an opinion concurring in part and dissenting in part, in which Kennedy, J., joined as to Part II, post, p. 296.

Miguel A. Estrada argued the cause for petitioner. With him on the briefs were Barbara L. Hartung, Mark E. Olive, and John H. Blume.

Pamela A. Rumpz, Assistant Attorney General of Virginia, argued the cause for respondent. With her on the brief was Mark L. Earley, Attorney General.^[*]

Justice Stevens delivered the opinion of the Court.^[†]

The District Court for the Eastern District of Virginia granted petitioner's application for a writ of habeas corpus and vacated his capital murder conviction and death sentence on the grounds that the Commonwealth had failed to disclose important exculpatory evidence and that petitioner had not, in consequence, received a fair trial. The Court of Appeals for the Fourth Circuit reversed because petitioner had not raised his constitutional claim at his trial or in state collateral proceedings. In addition, the Fourth Circuit concluded that petitioner's claim was, "in any event, without merit." App. 418, n. 8.^[1] Finding the legal question presented by this *266 case considerably more difficult than the Fourth Circuit, we granted certiorari, 525 U. S. 809 (1998), to consider (1) whether the Commonwealth violated Brady v. Maryland, 373 U. S. 83 (1963), and its progeny; (2) whether there was an acceptable "cause" for petitioner's failure to raise this claim in state court; and (3), if so, whether he suffered prejudice sufficient to excuse his procedural default.

I

In the early evening of January 5, 1990, Leanne Whitlock, an African-American sophomore at James Madison University, was abducted from a local shopping center and robbed and murdered. In separate trials, both petitioner and Ronald Henderson were convicted of all three offenses. Henderson was convicted of first-degree murder, a noncapital offense, whereas petitioner was convicted of capital murder and sentenced to death.^[2]

At both trials, a woman named Anne Stoltzfus testified in vivid detail about Whitlock's abduction. The exculpatory material that petitioner claims should have been disclosed before trial includes documents prepared by Stoltzfus, and notes of interviews with her, that impeach significant portions of her testimony. We begin, however, by noting that, even without the Stoltzfus testimony, the evidence in the record was sufficient to establish petitioner's guilt on the murder charge. Whether petitioner would have been convicted of capital murder and received the death sentence if she had not testified, or if she had been sufficiently impeached, is less clear. To put the question in context, we review the trial testimony at some length.

The Testimony at Trial

At about 4:30 p.m. on January 5, 1990, Whitlock borrowed a 1986 blue Mercury Lynx from her boyfriend, John Dean, *267 who worked in the Valley Shopping Mall in Harrisonburg, Virginia. At about 6:30 or 6:45 p.m., she left her apartment, intending to return the car to Dean at the mall. She did not return the car and was not again seen alive by any of her friends or family.

Petitioner's mother testified that she had driven petitioner and Henderson to Harrisonburg on January 5. She also testified that petitioner always carried a hunting knife that had belonged to his father. Two witnesses, a friend of Henderson's and a security guard, saw petitioner and Henderson at the mall that afternoon. The security guard was informed around 3:30 p.m. that two men, one of whom she identified at trial as petitioner, were attempting to steal a car in the parking lot. She had them under observation during the remainder of the afternoon but lost sight of them at about 6:45.

At approximately 7:30 p.m., a witness named Kurt Massie saw the blue Lynx at a location in Augusta County about 25 miles from Harrisonburg and a short distance from the cornfield where Whitlock's body was later found. Massie identified petitioner as the driver of the vehicle; he also saw a white woman in the front seat and another man in the back. Massie noticed that the car was muddy, and that it turned off Route 340 onto a dirt road.

At about 8 p.m., another witness saw the Lynx at Buddy's Market, with two men sitting in the front seat. The witness did not see anyone else in the car. At approximately 9 p.m., petitioner and Henderson arrived at Dice's Inn, a bar in Staunton, Virginia, where they stayed for about four or five hours. They danced with several women, including four prosecution witnesses: Donna Kay Tudor, Nancy Simmons, Debra Sievers, and Carolyn Brown. While there, Henderson gave Nancy Simmons a watch that had belonged to Whitlock. Petitioner spent most of his time with Tudor, who was later arrested for grand larceny based on her possession of the blue Lynx.

*268 These four women all testified that Tudor had arrived at Dice's at about 8 p.m. Three of them noticed nothing unusual about petitioner's appearance, but Tudor saw some blood on his jeans and a cut on his knuckle. Tudor also testified that she, Henderson, and petitioner left Dice's together after it closed to search for marijuana. Henderson was driving the blue Lynx, and petitioner and Tudor rode in back. Tudor related that petitioner was leaning toward Henderson and talking with him; she overheard a crude conversation that could reasonably be interpreted as describing the assault and murder of a black person with a "rock crusher." Tudor stated that petitioner made a statement that implied that he had killed someone, so the person "wouldn't give him no more trouble." App. 99. Tudor testified that while she, petitioner, and Henderson were driving around, petitioner took out his knife and threatened to stab Henderson because he was driving recklessly. Petitioner then began driving.

At about 4:30 or 5 a.m. on January 6, petitioner drove Henderson to Kenneth Workman's apartment in Timberville.^[3] Henderson went inside to get something, and petitioner and Tudor drove off without waiting for him. Workman testified that Henderson had blood on his pants and stated he had killed a black person.

Petitioner and Tudor then drove to a motel in Blue Ridge. A day or two later they went to Virginia Beach, where they spent the rest of the week. Petitioner gave Tudor pearl earrings that Whitlock had been wearing when she was last seen. Tudor saw Whitlock's driver's license and bank card in the glove compartment of the car. Tudor testified that petitioner unsuccessfully attempted to use Whitlock's bank card when they were in Virginia Beach.

When petitioner and Tudor returned to Augusta County, they abandoned the blue Lynx. On January 11, the police identified the car as Dean's, and found petitioner's and Tudor's *269 fingerprints on both the inside and the outside of the car. They also found shoe impressions that matched the soles of shoes belonging to petitioner. Inside the car, they retrieved a jacket that contained identification papers belonging to Henderson.

The police also recovered a bag at petitioner's mother's house that Tudor testified she and petitioner had left when they returned from Virginia Beach. The bag contained, among other items, three identification cards belonging to Whitlock and a black "tank top" shirt that was later found to have human blood and semen stains on it. Tr. 707.

On January 13, a farmer called the police to advise them that he had found Henderson's wallet; a search of the area led to the discovery of Whitlock's frozen, nude, and battered body. A 69-pound rock, spotted with blood, lay nearby. Forensic evidence indicated that Whitlock's death was caused by "multiple blunt force injuries to the head." App. 109. The location of the rock and the human blood on the rock suggested that it had been used to inflict these injuries. Based on the contents of Whitlock's stomach, the medical examiner determined that she died fewer than six hours after she had last eaten.^[4]

A number of Caucasian hair samples were found at the scene, three of which were probably petitioner's. Given the weight of the rock, the prosecution argued that one of the killers must have held the victim down while the other struck her with the murder weapon.

Donna Tudor's estranged husband, Jay Tudor, was called by the defense and testified that in March she had told him that she was present at the murder scene and that petitioner did not participate in the murder. Jay Tudor's testimony was inconsistent in several respects with that of other witnesses. For example, he testified that several days elapsed *270 between the time that petitioner, Henderson, and Donna Tudor picked up Whitlock and the time of Whitlock's murder. Anne Stoltzfus' Testimony

Anne Stoltzfus testified that on two occasions on January 5 she saw petitioner, Henderson, and a blonde girl inside the Harrisonburg mall, and that she later witnessed their abduction of Whitlock in the parking lot. She did not call the police, but a week and a half after the incident she discussed it with classmates at James Madison University, where both she and Whitlock were students. One of them called the police. The next night a detective visited her, and the following morning she went to the police station and told her story to Detective Claytor, a member of the Harrisonburg City Police Department. Detective Claytor showed her photographs of possible suspects, and she identified petitioner and Henderson "with absolute certainty" but stated that she had a slight reservation about her identification of the blonde woman. Id., at 56.

At trial, Stoltzfus testified that, at about 6 p.m. on January 5, she and her 14-year-old daughter were in the Music Land store in the mall looking for a compact disc. While she was waiting for assistance from a clerk, petitioner, whom she described as "Mountain Man," and the blonde girl entered.^[5]*271 Because petitioner was "revved up" and "very impatient," she was frightened and backed up, bumping into Henderson (whom she called "Shy Guy"), and thought she felt something hard in the pocket of his coat. Id., at 36-37.

Stoltzfus left the store, intending to return later. At about 6:45, while heading back toward Music Land, she again encountered the threesome: "Shy Guy" walking by himself, followed by the girl, and then "Mountain Man" yelling "Donna, Donna, Donna." The girl bumped into Stoltzfus and then asked for directions to the bus stop.^[6] The three then left.

At first Stoltzfus tried to follow them because of her concern about petitioner's behavior, but she "lost him" and then headed back to Music Land. The clerk had not returned, so she and her daughter went to their car. While driving to another store, they saw a shiny dark blue car. The driver was "beautiful," "well dressed and she was happy, she was singing . . . ." Id., at 41. When the blue car was stopped behind a minivan at a stop sign, Stoltzfus saw petitioner for the third time.

She testified:

"`Mountain Man' came tearing out of the Mall entrance door and went up to the driver of the van and . . . was just really mad and ran back and banged on back of the backside of the van and then went back to the Mall entrance wall where `Shy Guy' and `Blonde Girl' was standing . . . . [T]hen we left [and before the van and a white pickup truck could turn] `Mountain Man' came out again . . . ." Id., at 42-43.

After first going to the passenger side of the pickup truck, petitioner came back to the black girl's car, "pounded on" the passenger window, shook the car, yanked the door open and jumped in. When he motioned for "Blonde Girl" and "Shy *272 Guy" to get in, the driver stepped on the gas and "just laid on the horn" but she could not go because there were people walking in front of the car. The horn "blew a long time" and petitioner

"started hitting her . . . on the left shoulder, her right shoulder and then it looked like to me that he started hitting her on the head and I was, I just became concerned and upset. So I beeped, honked my horn and then she stopped honking the horn and he stopped hitting her and opened the door again and the `Blonde Girl' got in the back and `Shy Guy' followed and got behind him." Id., at 44-45.

Stoltzfus pulled her car up parallel to the blue car, got out for a moment, got back in, and leaned over to ask repeatedly if the other driver was "O.K." The driver looked "frozen" and mouthed an inaudible response. Stoltzfus started to drive away and then realized "the only word that it could possibly be, was help." Id., at 47. The blue car then drove slowly around her, went over the curb with its horn honking, and headed out of the mall. Stoltzfus briefly followed, told her daughter to write the license number on a "3x4 [inch] index card,"^[7] and then left for home because she had an empty gas tank and "three kids at home waiting for supper." Id., at 48-49.

At trial Stoltzfus identified Whitlock from a picture as the driver of the car and pointed to petitioner as "Mountain Man." When asked if pretrial publicity about the murder had influenced her identification, Stoltzfus replied "absolutely not." She explained:

"[F]irst of all, I have an exceptionally good memory. I had very close contact with [petitioner] and he made an *273 emotional impression with me because of his behavior and I, he caught my attention and I paid attention. So I have absolutely no doubt of my identification." Id., at 58.

The Commonwealth did not produce any other witnesses to the abduction. Stoltzfus' daughter did not testify.

The Stoltzfus Documents

The materials that provide the basis of petitioner's Brady claim consist of notes taken by Detective Claytor during his interviews with Stoltzfus, and letters written by Stoltzfus to Claytor. They cast serious doubt on Stoltzfus' confident assertion of her "exceptionally good memory." Because the content of the documents is critical to petitioner's procedural and substantive claims, we summarize their content.

Exhibit 1^[8] is a handwritten note prepared by Detective Claytor after his first interview with Stoltzfus on January 19, 1990, just two weeks after the crime. The note indicates that she could not identify the black female victim. The only person Stoltzfus apparently could identify at this time was the white female. Id., at 306.

Exhibit 2 is a document prepared by Detective Claytor some time after February 1. It contains a summary of his interviews with Stoltzfus conducted on January 19 and January 20, 1990.^[9] At that time "she was not sure whether she could identify the white males but felt sure she could identify the white female."

*274 Exhibit 3 is entitled "Observations" and includes a summary of the abduction.

Exhibit 4 is a letter written by Stoltzfus to Claytor three days after their first interview "to clarify some of my confusion for you." The letter states that she had not remembered being at the mall, but that her daughter had helped jog her memory. Her description of the abduction includes the comment: "I have a very vague memory that I'm not sure of. It seems as if the wild guy that I saw had come running through the door and up to a bus as the bus was pulling off. . . . Then the guy I saw came running up to the black girl's window. Were those 2 memories the same person?" Id., at 316. In a postscript she noted that her daughter "doesn't remember seeing the 3 people get into the black girl's car . . . ." Ibid.

Exhibit 5 is a note to Claytor captioned "My Impressions of `The Car,' " which contains three paragraphs describing the size of the car and comparing it with Stoltzfus' Volkswagen Rabbit, but not mentioning the license plate number that she vividly recalled at the trial. Id., at 317-318.

Exhibit 6 is a brief note from Stoltzfus to Claytor dated January 25, 1990, stating that after spending several hours with John Dean, Whitlock's boyfriend, "looking at current photos," she had identified Whitlock "beyond a shadow of a doubt."^[10]Id., at 318. The District Court noted that by the time of trial her identification had been expanded to include a description of her clothing and her appearance as a college kid who was "singing" and "happy." Id., at 387-388.

Exhibit 7 is a letter from Stoltzfus to Detective Claytor, dated January 16, 1990, in which she thanks him for his "patience with my sometimes muddled memories." She states that if the student at school had not called the police, "I never would have made any of the associations that you helped me make." Id., at 321.

*275 In Exhibit 8, which is undated and summarizes the events described in her trial testimony, Stoltzfus commented:

"So where is the 3x4 card? . . . It would have been very nice if I could have remembered all this at the time and had simply gone to the police with the information. But I totally wrote this off as a trivial episode of college kids carrying on and proceeded with my own full-time college load at JMU. . . . Monday, January 15th. I was cleaning out my car and found the 3x4 card. I tore it into little pieces and put it in the bottom of a trash bag." Id., at 326.

There is a dispute between the parties over whether petitioner's counsel saw Exhibits 2, 7, and 8 before trial. The prosecuting attorney conceded that he himself never saw Exhibits 1, 3, 4, 5, and 6 until long after petitioner's trial, and they were not in the file he made available to petitioner.^[11] For purposes of this case, therefore, we assume that petitioner proceeded to trial without having seen Exhibits 1, 3, 4, 5, and 6.^[12]

*276 State Proceedings

Petitioner was tried in Augusta County, where Whitlock's body was found, on charges of capital murder, robbery, and abduction. Because the prosecutor maintained an open file policy, which gave petitioner's counsel access to all of the evidence in the Augusta County prosecutor's files,^[13] petitioner's counsel did not file a pretrial motion for discovery of possible exculpatory evidence.^[14] In closing argument, petitioner's lawyer effectively conceded that the evidence was sufficient to support the robbery and abduction charges, as well as the lesser offense of first-degree murder, but argued that the evidence was insufficient to prove that petitioner was guilty of capital murder. Id., at 192-193.

The judge instructed the jury that petitioner could be found guilty of the capital charge if the evidence established beyond a reasonable doubt that he "jointly participated in the fatal beating" and "was an active and immediate participant *277 in the act or acts that caused the victim's death." Id., at 160-161. The jury found petitioner guilty of abduction, robbery, and capital murder. Id., at 200-201. After listening to testimony and arguments presented during the sentencing phase, the jury made findings of "vileness" and "future dangerousness," and unanimously recommended the death sentence that the judge later imposed.

The Virginia Supreme Court affirmed the conviction and sentence. Strickler v. Commonwealth, 241 Va. 482, 404 S. E. 2d 227 (1991). It held that the trial court had properly instructed the jury on the "joint perpetrator" theory of capital murder and that the evidence, viewed most favorably in support of the verdict, amply supported the prosecution's theory that both petitioner and Henderson were active participants in the actual killing.^[15]

In December 1991, the Augusta County Circuit Court appointed new counsel to represent petitioner in state habeas corpus proceedings. State habeas counsel advanced an *278 ineffective-assistance-of-counsel claim based, in part, on trial counsel's failure to file a motion under Brady v. Maryland, 373 U. S. 83 (1963), "to have the Commonwealth disclose to the defense all exculpatory evidence known to it—or in its possession." App. 205-206. In answer to that claim, the Commonwealth asserted that such a motion was unnecessary because the prosecutor had maintained an open file policy.^[16] The Circuit Court dismissed the petition, and the State Supreme Court affirmed. Strickler v. Murray, 249 Va. 120, 452 S. E. 2d 648 (1995).

Federal Habeas Corpus Proceedings

In March 1996, petitioner filed a federal habeas corpus petition in the Eastern District of Virginia. The District Court entered a sealed, ex parte order granting petitioner's counsel the right to examine and to copy all of the police and prosecution files in the case. Record, Doc. No. 20. That order led to petitioner's counsel's first examination of the Stoltzfus materials, described supra, at 273-275.

Based on the discovery of those exhibits, petitioner for the first time raised a direct claim that his conviction was invalid because the prosecution had failed to comply with the rule of Brady v. Maryland. The District Court granted the Commonwealth's motion to dismiss all claims except for petitioner's contention that the Commonwealth violated Brady, that he received ineffective assistance of counsel,^[17] and that he was denied due process of law under the Fifth and Fourteenth Amendments. In its order denying the Commonwealth's motion to dismiss, the District Court found that petitioner had "demonstrated cause for his failure to raise this claim earlier [because] [d]efense counsel had no independent access to this material and the Commonwealth repeatedly withheld it throughout Petitioner's state habeas proceeding." App. 287.

*279 After reviewing the Stoltzfus materials, and making the assumption that the three disputed exhibits had been available to the defense, the District Court concluded that the failure to disclose the other five was sufficiently prejudicial to undermine confidence in the jury's verdict. Id., at 396. It granted summary judgment to petitioner and granted the writ.

The Court of Appeals vacated in part and remanded. It held that petitioner's Brady claim was procedurally defaulted because the factual basis for the claim was available to him at the time he filed his state habeas petition. Given that he knew that Stoltzfus had been interviewed by Harrisonburg police officers, the court opined that "reasonably competent counsel would have sought discovery in state court" of the police files, and that in response to this "simple request, it is likely the state court would have ordered the production of the files." App. 421. Therefore, the Court of Appeals reasoned, it could not address the Brady claim unless petitioner could demonstrate both cause and actual prejudice.

Under Fourth Circuit precedent a party "cannot establish cause to excuse his default if he should have known of such claims through the exercise of reasonable diligence." App. 423 (citing Stockton v. Murray, 41 F. 3d 920, 925 (1994)). Having already decided that the claim was available to reasonably competent counsel, the Fourth Circuit stated that the basis for finding procedural default also foreclosed a finding of cause. Moreover, the Court of Appeals reasoned, petitioner could not fault his trial lawyers' failure to make a Brady claim because they reasonably relied on the prosecutor's open file policy. App. 423-424.^[18]

As an alternative basis for decision, the Court of Appeals also held that petitioner could not establish prejudice because *280 "the Stoltzfus materials would have provided little or no help .. . in either the guilt or sentencing phases of the trial." Id., at 425. With respect to guilt, the court noted that Stoltzfus' testimony was not relevant to petitioner's argument that he was only guilty of first-degree murder rather than capital murder because Henderson, rather than he, actually killed Whitlock. With respect to sentencing, the court concluded that her testimony "was of no import" because the findings of future dangerousness and vileness rested on other evidence. Finally, the court noted that even if it could get beyond the procedural default, the Brady claim would fail on the merits because of the absence of prejudice. App. 425, n. 11. The Court of Appeals, therefore, reversed the District Court's judgment and remanded the case with instructions to dismiss the petition.

II

The first question that our order granting certiorari directed the parties to address is whether the Commonwealth violated the Brady rule. We begin our analysis by identifying the essential components of a Brady violation.

In Brady, this Court held "that the suppression by the prosecution of evidence favorable to an accused upon request violates due process where the evidence is material either to guilt or to punishment, irrespective of the good faith or bad faith of the prosecution." 373 U. S., at 87. We have since held that the duty to disclose such evidence is applicable even though there has been no request by the accused, United States v. Agurs, 427 U. S. 97, 107 (1976), and that the duty encompasses impeachment evidence as well as exculpatory evidence, United States v. Bagley, 473 U. S. 667, 676 (1985). Such evidence is material "if there is a reasonable probability that, had the evidence been disclosed to the defense, the result of the proceeding would have been different." Id., at 682; see also Kyles v. Whitley, 514 U. S. 419, 433-434 (1995). Moreover, the rule encompasses evidence "known only to police *281 investigators and not to the prosecutor." Id., at 438. In order to comply with Brady, therefore, "the individual prosecutor has a duty to learn of any favorable evidence known to the others acting on the government's behalf in this case, including the police." Kyles, 514 U. S., at 437.

These cases, together with earlier cases condemning the knowing use of perjured testimony,^[19] illustrate the special role played by the American prosecutor in the search for truth in criminal trials. Within the federal system, for example, we have said that the United States Attorney is "the representative not of an ordinary party to a controversy, but of a sovereignty whose obligation to govern impartially is as compelling as its obligation to govern at all; and whose interest, therefore, in a criminal prosecution is not that it shall win a case, but that justice shall be done." Berger v. United States, 295 U. S. 78, 88 (1935).

This special status explains both the basis for the prosecution's broad duty of disclosure and our conclusion that not every violation of that duty necessarily establishes that the outcome was unjust. Thus the term "Brady violation" is sometimes used to refer to any breach of the broad obligation to disclose exculpatory evidence^[20]—that is, to any suppression of so-called "Brady material"—although, strictly speaking, there is never a real "Brady violation" unless the nondisclosure was so serious that there is a reasonable probability that the suppressed evidence would have produced a different verdict. There are three components of a true Brady violation: The evidence at issue must be favorable to the accused, *282 either because it is exculpatory, or because it is impeaching; that evidence must have been suppressed by the State, either willfully or inadvertently; and prejudice must have ensued.

Two of those components are unquestionably established by the record in this case. The contrast between (a) the terrifying incident that Stoltzfus confidently described in her testimony and (b) her initial perception of that event "as a trivial episode of college kids carrying on" that her daughter did not even notice, suffices to establish the impeaching character of the undisclosed documents.^[21] Moreover, with respect to at least five of those documents, there is no dispute about the fact that they were known to the Commonwealth but not disclosed to trial counsel. It is the third component—whether petitioner has established the prejudice necessary to satisfy the "materiality" inquiry—that is the most difficult element of the claimed Brady violation in this case.

Because petitioner acknowledges that his Brady claim is procedurally defaulted, we must first decide whether that default is excused by an adequate showing of cause and prejudice. In this case, cause and prejudice parallel two of the three components of the alleged Brady violation itself. The suppression of the Stoltzfus documents constitutes one of the causes for the failure to assert a Brady claim in the state courts, and unless those documents were "material" for Brady purposes, their suppression did not give rise to sufficient prejudice to overcome the procedural default.

III

Respondent expressly disavows any reliance on the fact that petitioner's Brady claim was not raised at trial. Brief *283 for Respondent 17-18, n. 6. He states that the Commonwealth has consistently argued "that the claim is defaulted because it could have been raised on state habeas corpus through the exercise of due diligence, but was not." Ibid. Despite this concession, it is appropriate to begin the analysis of the "cause" issue by explaining why petitioner's reasons for failing to raise his Brady claim at trial are acceptable under this Court's cases.

Three factors explain why trial counsel did not advance this claim: The documents were suppressed by the Commonwealth; the prosecutor maintained an open file policy;^[22] and trial counsel were not aware of the factual basis for the claim. The first and second factors—i. e., the nondisclosure and the open file policy—are both fairly characterized as conduct attributable to the Commonwealth that impeded trial counsel's access to the factual basis for making a Brady claim.^[23] As we explained in Murray v. Carrier, 477 U. S. 478, 488 (1986), it is just such factors that ordinarily establish the existence of cause for a procedural default.^[24]

*284 If it was reasonable for trial counsel to rely on, not just the presumption that the prosecutor would fully perform his duty to disclose all exculpatory materials, but also the implicit representation that such materials would be included in the open files tendered to defense counsel for their examination, we think such reliance by counsel appointed to represent petitioner in state habeas proceedings was equally reasonable. Indeed, in Murray we expressly noted that "the standard for cause should not vary depending on the timing of a procedural default." Id., at 491.

Respondent contends, however, that the prosecution's maintenance of an open file policy that did not include all it was purported to contain is irrelevant because the factual basis for the assertion of a Brady claim was available to state habeas counsel. He presses two factors to support this assertion. First, he argues that an examination of Stoltzfus' trial testimony,^[25] as well as a letter published in a local newspaper,^[26] made it clear that she had had several interviews with Detective Claytor. Second, the fact that the Federal District Court entered an order allowing discovery of the Harrisonburg police files indicates that diligent counsel could *285 have obtained a similar order from the state court. We find neither factor persuasive.

Although it is true that petitioner's lawyers—both at trial and in post-trial proceedings—must have known that Stoltzfus had had multiple interviews with the police, it by no means follows that they would have known that records pertaining to those interviews, or that the notes that Stoltzfus sent to the detective, existed and had been suppressed.^[27] Indeed, if respondent is correct that Exhibits 2, 7, and 8 were in the prosecutor's "open file," it is especially unlikely that counsel would have suspected that additional impeaching evidence was being withheld. The prosecutor must have known about the newspaper articles and Stoltzfus' meetings with Claytor, yet he did not believe that his prosecution file was incomplete.

Furthermore, the fact that the District Court entered a broad discovery order even before federal habeas counsel had advanced a Brady claim does not demonstrate that a state court also would have done so.^[28] Indeed, as we understand Virginia law and respondent's position, petitioner would not have been entitled to such discovery in state habeas *286 proceedings without a showing of good cause.^[29] Even pursuant to the broader discovery provisions afforded at trial, petitioner would not have had access to these materials under Virginia law, except as modified by Brady.^[30] Mere speculation that some exculpatory material may have been withheld is unlikely to establish good cause for a discovery request on collateral review. Nor, in our opinion, should such suspicion suffice to impose a duty on counsel to advance a claim for which they have no evidentiary support. Proper respect for state procedures counsels against a requirement that all possible claims be raised in state collateral proceedings, even when no known facts support them. The presumption, well established by "`tradition and experience,' " that prosecutors have fully "`discharged their official duties,' " United States v. Mezzanatto, 513 U. S. 196, 210 (1995), is inconsistent with the novel suggestion that conscientious defense counsel have a procedural obligation to assert constitutional *287 error on the basis of mere suspicion that some prosecutorial misstep may have occurred.

Respondent's position on the "cause" issue is particularly weak in this case because the state habeas proceedings confirmed petitioner's justification for his failure to raise a Brady claim. As already noted, when he alleged that trial counsel had been incompetent because they had not advanced such a claim, the warden responded by pointing out that there was no need for counsel to do so because they "were voluntarily given full disclosure of everything known to the government."^[31] Given that representation, petitioner had no basis for believing the Commonwealth had failed to comply with Brady at trial.^[32]

Respondent also argues that our decisions in Gray v. Netherland, 518 U. S. 152 (1996), and McCleskey v. Zant, 499 U. S. 467 (1991), preclude the conclusion that the cause for petitioner's default was adequate. In both of those cases, however, the petitioner was previously aware of the factual basis for his claim but failed to raise it earlier. See Gray, 518 U. S., at 161; McCleskey, 499 U. S., at 498-499. In the context of a Brady claim, a defendant cannot conduct the "reasonable *288 and diligent investigation" mandated by McCleskey to preclude a finding of procedural default when the evidence is in the hands of the State.^[33]

The controlling precedents on "cause" are Murray v. Carrier, 477 U. S., at 488, and Amadeo v. Zant, 486 U. S. 214 (1988). As we explained in the latter case:

"If the District Attorney's memorandum was not reasonably discoverable because it was concealed by Putnam County officials, and if that concealment, rather than tactical considerations, was the reason for the failure of petitioner's lawyers to raise the jury challenge in the trial court, then petitioner established ample cause to excuse his procedural default under this Court's precedents." Id., at 222.^[34]

There is no suggestion that tactical considerations played any role in petitioner's failure to raise his Brady claim in state court. Moreover, under Brady an inadvertent nondisclosure has the same impact on the fairness of the proceedings as deliberate concealment. "If the suppression of evidence results in constitutional error, it is because of the character of the evidence, not the character of the prosecutor." Agurs, 427 U. S., at 110.

*289 In summary, petitioner has established cause for failing to raise a Brady claim prior to federal habeas because (a) the prosecution withheld exculpatory evidence; (b) petitioner reasonably relied on the prosecution's open file policy as fulfilling the prosecution's duty to disclose such evidence; and (c) the Commonwealth confirmed petitioner's reliance on the open file policy by asserting during state habeas proceedings that petitioner had already received "everything known to the government."^[35] We need not decide in this case whether any one or two of these factors would be sufficient to constitute cause, since the combination of all three surely suffices.

IV

The differing judgments of the District Court and the Court of Appeals attest to the difficulty of resolving the issue of prejudice. Unlike the Fourth Circuit, we do not believe that "the Stolzfus [sic] materials would have provided little or no help to Strickler in either the guilt or sentencing phases of the trial." App. 425. Without a doubt, Stoltzfus' testimony was prejudicial in the sense that it made petitioner's conviction more likely than if she had not testified, and discrediting her testimony might have changed the outcome of the trial.

That, however, is not the standard that petitioner must satisfy in order to obtain relief. He must convince us that "there is a reasonable probability" that the result of the trial would have been different if the suppressed documents had been disclosed to the defense. As we stressed in Kyles: "[T]he adjective is important. The question is not whether the defendant would more likely than not have received a