concurring and dissenting:
I join in holding that Lewis Bond was not prejudiced by the challenged jury instruction. See United States v. Frady, 456 U.S. 152, 169-74, 102 S.Ct. 1584, 1595-97, 71 L.Ed.2d 816 (1982). I dissent from the denial of Bond’s request for an evidentiary hearing to determine whether the prosecution withheld exculpatory material. I would probe more deeply into the circumstances of Michael Brown’s death.
I
In his pro se petition, Bond alleges that a police officer overheard Edward Roberts confess to the crime for which Bond has been convicted. Bond also alleges that the police tape recorded an interview with Haywood Williams in which Williams described Roberts’s confession. Bond asserts that this exculpatory material was not disclosed despite his request, thereby violating the Due Process Clause of the fourteenth amendment. See Brady v. Maryland, 373 U.S. 83, 87, 83 S.Ct. 1194, 1196, 10 L.Ed.2d 215 (1963). Bond’s petition suggests that the prosecution violated the Due Process Clause in two respects. First, the prosecution failed to disclose obviously exculpatory material. See Brady, 373 U.S. at 87, 83 S.Ct. at 1196. Second, the allegation that a police officer overheard Roberts confess indicates that the prosecution countenanced perjury when it allowed Roberts to testify that Bond had committed the crime. See Giglio v. United States, 405 U.S. 150, 153, 92 S.Ct. 763, 765, 31 L.Ed.2d 104 (1972).
With his petition, Bond submitted an affidavit from Williams in support of these allegations. The state filed a motion under Federal Rule of Civil Procedure 12(b)(6) asserting that the petition failed to state a claim for relief. The state denied that any evidence was suppressed and argued that the allegations in Bond’s petition were too conclusory to merit relief. The state also claimed that the petition failed to allege how the evidence was obviously exculpatory or how the state should have recognized its exculpatory nature. On appeal the state has also argued that the evidence was not material. The district court granted the motion and dismissed Bond’s petition without an evidentiary hearing. Bond’s earlier habeas petition in state court was likewise dismissed without a hearing.
The Supreme Court has held that “[wjhere the facts are in dispute, the federal court in habeas corpus must hold an evidentiary hearing if the habeas applicant did not receive a full and fair evidentiary hearing in a state court, either at the time of the trial or in a collateral proceeding.” Townsend v. Sain, 372 U.S. 293, 312, 83 S.Ct. 745, 757, 9 L.Ed.2d 770 (1963). It is clear from Townsend that because Bond never received a hearing in state court, he must be afforded a hearing in federal court.
The district court dismissed Bond’s petition because it did not believe Williams’s affidavit. The court stated that “[t]he pri- or convictions and criminal activity of Haywood Williams are well known in this court. The court finds no credibility in the statements made in his affidavit and, therefore, rejects his statements as not believable.”
The district court erred in discrediting Williams’s affidavit on the basis of his “pri- or convictions and criminal activity,” none of which is part of the record in this case. Whenever a court considers matters outside the pleadings, it must convert the motion to dismiss into a motion for summary judgment, “and all parties shall be given reasonable opportunity to present all material made pertinent to such a motion by Rule 56.” Fed.R.Civ.P. 12(b). See Carter v. Stanton, 405 U.S. 669, 671, 92 S.Ct. 1232, 1234, 31 L.Ed.2d 569 (1972) (per cu-riam); Plante v. Shivar, 540 F.2d 1233, 1234-35 (4th Cir.1976) (per curiam). The *466district court failed to follow these mandatory procedures.
Moreover, a decision based on matters outside the record is impermissible because it does not afford the appellate court a basis on which to conduct its review. Credibility determinations can only be made after the judge has had the opportunity to observe the affiant in court. “It is only when the witnesses are present and subject to cross-examination that their credibility and the weight to be given their testimony can be appraised.” Poller v. Columbia Broadcasting System, Inc., 368 U.S. 464, 473, 82 S.Ct. 486, 491, 7 L.Ed.2d 458 (1962); see RKO General, Inc. v. Federal Communications Commission, 670 F.2d 215, 225 (D.C.Cir.1981) (error to deny hearing “with the bald statement that RKO’s affidavits were ‘not credible’ ”). Thus, it was error for the district court to brush aside Williams’s affidavit without holding an eviden-tiary hearing.
Even if the district court had been free to reject Williams’s affidavit, it could not have granted the government’s motion to dismiss under Rule 12(b)(6). “[A] complaint should not be dismissed for failure to state a claim unless it appears beyond doubt that the plaintiff can prove no set of facts in support of his claim which would entitle him to relief.” Conley v. Gibson, 355 U.S. 41, 45-46, 78 S.Ct. 99, 101-02, 2 L.Ed.2d 80 (1957) (footnote omitted); accord Hishon v. King & Spalding, 467 U.S. 69, 104 S.Ct. 2229, 2233, 81 L.Ed.2d 59 (1984). Bond alleges that the police overheard Roberts confess to the crime. He also asserts the existence of tape recordings that would support his claim even if Williams’s affidavit were disbelieved. These allegations are not mere legal conclusions that are insufficient to survive a motion to dismiss. In Machibroda v. United States, 368 U.S. 487, 495, 82 S.Ct. 510, 514, 7 L.Ed.2d 473 (1962), the Court explained the principles that govern this aspect of the ease:
The petitioner’s motion and affidavit contain charges which are detailed and specific---- “Not by the pleadings and the affidavits, but by the whole of the testimony, must it be determined whether the petitioner has carried his burden of proof and shown his right to a discharge. The Government’s contention that his allegations are improbable and unbelievable cannot serve to deny him an opportunity to support them by evidence. On this record it is his right to be heard.”
Accordingly, the district court erred in granting the government’s motion to dismiss Bond’s complaint for failure to state a claim.*
II
If Bond’s allegations are true, the evidence that was suppressed was material to his trial. The Supreme Court has adopted the following standard for determining whether evidence is material:
The evidence 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, — U.S.-, 105 S.Ct. 3375, 3384, 3385, 87 L.Ed.2d 481 (1985).
Roberts was the only eye witness to testify at Bond’s trial. Without his testimony, Bond could not have been convicted. It is true that Roberts was cross-examined as to his motive to lie. It is also true that the jury was informed that Roberts originally had been charged with the crime. However, to ask the jury to infer that Roberts was lying is far different from presenting *467direct evidence of his guilt. Bond would have been in a much better position to cast doubt on the testimony of his principal accuser if he had been able to present evidence of Roberts’s confession. In addition to impeaching Roberts, this evidence would also tend to exculpate Bond. Williams’s testimony would be admissible as substantive evidence that Bond did not kill Brown. At Bond’s trial, the truth of Roberts’s confession, and the credibility of Williams, who repeated the confession, would have been issues for the jury. See Morris v. Commonwealth, 229 Va. 145, 326 S.E.2d 693 (1985). Bond’s inability to develop this evidence clearly is “sufficient to undermine confidence” in his conviction. Bagley, 105 S.Ct. at 3384. Accordingly, I would remand this case for an evidentiary hearing to determine whether the prosecution failed to disclose evidence that Roberts had confessed to the crime for which Bond stands convicted.
For cases that have recognized a petitioner's right to an evidentiary hearing under facts similar to those presented in this case, see Lindhorst v. United States, 585 F.2d 361, 365 (8th Cir.1978) ("The district judge cannot credit the recanting witnesses’ trial testimony and discredit their affidavits without affording appellant an opportunity to prove the allegations.”), and Schneider v. Estelle, 552 F.2d 593 (5th Cir.1977) (petitioner entitled to hearing on claim that policeman committed perjury where allegation is supported by affidavit from government informant).