Giglio v. United States
Citation: 405 U.S. 150 (1972)
Facts
Giglio was convicted of passing forged money orders. A key witness was a co-conspirator who testified for the government. An Assistant U.S. Attorney had promised the witness he would not be prosecuted if he cooperated, but a different AUSA denied any such promise at trial. The promise was not disclosed to the defense.
Issue
Does the failure to disclose a promise of leniency made to a key government witness constitute a due process violation requiring a new trial?
Holding
Yes. The suppression of the promise of non-prosecution, which was material to the witness’s credibility, violated due process and entitled Giglio to a new trial.
Rule
Giglio disclosure: The prosecution must disclose to the defense any agreements, promises, or inducements made to witnesses in exchange for their testimony. Such evidence is material because it bears on the witness’s credibility (impeachment evidence). Brady obligations extend to impeachment evidence.
Significance
- Extends Brady v. Maryland (exculpatory evidence) to impeachment evidence — evidence bearing on a witness’s credibility, not just on guilt or innocence
- The prosecution is charged with knowledge of promises made by any member of its team, including other prosecutors in the office
- Giglio + Brady = the government’s disclosure obligations; collectively called “Brady/Giglio material”
- Materiality standard: evidence is material if there is a reasonable probability that disclosure would have produced a different result (United States v. Bagley)