legally operative facts

In October 1977 respondent Hughes Anderson Bagley was indicted in the Western District of Washington on fifteen counts of violating federal narcotics and firearms statutes. On November 18, 1977, twenty-four days before trial, Bagley filed a discovery motion requesting the names and addresses of government witnesses, their prior criminal records, and any deals, promises or inducements made to witnesses in exchange for their testimony. The government's response identified James F. O'Connor and Donald E. Mitchell as its two principal witnesses and stated that each had been paid $250 for information and expenses. It produced forms signed by both men entitled "Contract for Purchase of Information and Payment of Cash Reward" showing the $250 payments. O'Connor and Mitchell were state law-enforcement officers employed by the Milwaukee Railroad as private security guards. Between April and June 1977 they assisted the federal Bureau of Alcohol, Tobacco and Firearms in an undercover investigation of Bagley. At the December 1977 bench trial O'Connor and Mitchell testified that they had observed Bagley selling a handgun to a third person and test-firing several weapons. The district court found Bagley guilty on the narcotics charges, acquitted him on the firearms charges, and sentenced him to a total of twenty years' imprisonment, all but two years of which were suspended. In mid-1980 Bagley filed requests under the Freedom of Information Act and the Privacy Act and received copies of additional ATF contracts that O'Connor and Mitchell had signed on May 3, 1977. Each contract was entitled "Contract for Purchase of Information and Payment of Lump Sum Therefor." The printed portion stated that the vendor would provide information to ATF and that upon accomplishment of the objective the United States would pay a sum commensurate with services and information rendered. The typewritten description stated that each man would provide information regarding violations committed by Bagley, purchase evidence for ATF, work undercover, assist in gathering evidence, and testify against the violator in federal court. The contracts also provided for monthly payments of $300 up to a maximum of $3,000 and a $2,500 reward for information leading to arrest and conviction. On the basis of the newly obtained contracts Bagley moved under 28 U.S.C. § 2255 to vacate his sentence, alleging that the government's failure to disclose the contracts violated his right to due process. After an evidentiary hearing before a magistrate, the district court denied the motion, finding beyond a reasonable doubt that disclosure of the agreements would have had no effect on its finding of guilt. The Court of Appeals for the Ninth Circuit reversed. The Supreme Court granted certiorari.