D and Sewell, registered in a motel as man and wife. They were assigned a room without a bath. D was wearing a bowie knife in a sheath and carried another knife in his pocket. According to the testimony of his estranged wife, Sewell had had $360 in cash on his person two hours before. About 15 minutes later three motel employees heard respondent screaming for help. A forced entry into their room disclosed Sewell on top of D struggling for possession of the bowie knife. She was holding the knife; his bleeding hand grasped the blade. Sewell was trying to jam the blade into her chest. The employees separated the two and summoned the authorities. D departed without comment before they arrived. Sewell was dead on arrival at the hospital. Evidence showed that the parties had completed an act of intercourse, that Sewell had then gone to the bathroom down the hall, and that the struggle occurred upon his return. The contents of his pockets were in disarray on the dresser, and no money was found. The jury may have inferred that D took Sewell's money and that the fight started when Sewell re-entered the room and saw what she was doing. D surrendered to the police. There were no cuts or bruises of any kind, except needle marks on her upper arm. Sewell had several deep stab wounds in his chest and abdomen, and a number of slashes on his arms and hands, characterized by the pathologist as 'defensive wounds.' D's sole defense, made by her attorney, was that Sewell had initially attacked her with the knife and that her actions had all been directed toward saving her own life. D had screamed for help. Sewell was on top of her when help arrived, and his possession of two knives indicated that he was a violence-prone person. It took the jury about 25 minutes to elect a foreman and return a verdict. Three months later D filed a motion for a new trial because it was discovered (1) that Sewell had a prior criminal record that would have further evidenced his violent character; (2) that the prosecutor had failed to disclose this information to the defense; and (3) that a recent opinion of the United States Court of Appeals for the District of Columbia Circuit made it clear that such evidence was admissible even if not known to the defendant. The record included a plea of guilty to a charge of assault and carrying a deadly weapon in 1963 and another guilty plea to a charge of carrying a deadly weapon in 1971. Both weapons were knives. The Government (P) opposed the motion, there was no request for the information, and it was not material. The motion was denied. The Court of Appeals reversed. It held that the evidence was material and that its nondisclosure required a new trial because the jury might have returned a different verdict if the evidence had been received. The Supreme Court granted certiorari.