Where the evidence showed that the prosecution failed to disclose (1) that one witness had been intensively coached by police and prosecutors, and (2) that another witness was a paid informant, the federal appellate court erred in dismissing the defendant’s Brady v. Maryland claim and denying the defendant a certificate of appealability. In this capital case arising under pre-AEDPA habeas law, the defendant satisfied all three elements of a successful Brady claim: the evidence was exculpatory or impeaching, the evidence was suppressed by the government, and the evidence was material. Further, the defendant showed cause for failing to present the claim in state court, since he reasonably relied on the government’s assertion that the defense had received all relevant information during those proceedings.