Whether the Government’s failure to disclose requested evidence of possible payments to its witnesses required automatic reversal as a violation of the Confrontation Clause.
Holding
No. Impeachment evidence is covered by Brady, but its suppression warrants reversal only when it is material to the outcome; it does not trigger automatic reversal merely because it could have aided cross-examination.
Reasoning
Brady requires disclosure of favorable evidence that is material to guilt or punishment. Favorable evidence includes impeachment evidence, because proof that a Government witness has a bias, interest, or incentive to lie can affect the factfinder’s assessment of guilt. Giglio therefore places impeachment evidence within the Brady doctrine.
The Ninth Circuit incorrectly treated the nondisclosure as the equivalent of a direct restriction on cross-examination under Davis v. Alaska. In Davis, the trial judge barred defense counsel from pursuing a particular, relevant line of cross-examination. Here, Bagley was legally free to question O’Connor and Mitchell about bias; the claimed constitutional defect was that the Government failed to provide information that could have made that questioning more effective.
A Brady violation is concerned with whether suppression deprived the accused of a fair trial, not with whether undisclosed evidence might have been useful in some abstract sense. Thus, a conviction may be reversed only when the withheld evidence is material in the sense that its suppression undermines confidence in the result.