1959 – Napue v. Illinois
The principal state witness in a murder trial was asked by an Assistant District Attorney whether he had received consideration in exchange for his testimony. The witness said that he had not. The ADA knew this to be false but did not reveal it. The U.S. Supreme Court held that the due process clause of the Fourteenth Amendment bars prosecutors from presenting false testimony and requires
1963 – Brady v. Maryland
Petitioner and a companion were both convicted of first-degree murder and sentenced to death. The companion made a series of statements, one of which indicated that it was he, and not the petitioner, who actually committed the murder. Prosecutors turned over all of the companion’s statements except the one that exculpated the petitioner. In Brady v. Maryland, the U.S. Supreme Court held that suppression of evidence favorable to the accused by the prosecution violates due process where the evidence is material either to guilt or to punishment, irrespective of the good faith or bad faith of the prosecution.
1972 – Giglio v. United States
A key witness against Petitioner testified at trial that he had not received a promise for leniency from the state in return for his testimony. Unbeknownst to the trial prosecutor, the witness had in fact received a promise for leniency from another prosecutor in the office. Petitioner discovered this and filed a motion for a new trial. The U.S. Supreme Court held that the prosecution was obligated to disclose to the defense any promise or expectation of leniency it offered to a witness. It clarified that the state’s Brady obligation extends to all prosecutors in the office, and that it is up to such offices to create systems to ensure that such information is disclosed. Further, the Court clarified that impeachment evidence – evidence affecting the credibility of a witness – is Brady material and must be disclosed.
1976 – United States v. Agurs
Petitioner was convicted of murder after a trial in which he argued he had acted in self-defense. Subsequently petitioner sought a new trial because the state had failed to disclose the victim’s criminal record. The U.S. Supreme Court held that there was little difference between a general request by defense counsel for Brady material and the absence of a request altogether, and it found that prosecutors are obligated to turn over exculpatory evidence whether or not defense counsel asks for it.
1985 – United States v. Bagley
Respondent was indicted on firearms and narcotics charges. Prior to trial, he requested that the prosecution disclose any “deals, promises, or inducements” made to witnesses in exchange for their testimony. The prosecution did not disclose that its two principal witnesses worked with the Bureau of Alcohol, Tobacco, and Firearms (ATF) in an undercover investigation of respondent. Respondent sought a new trial under Brady v. Maryland. The U.S. Supreme Court again held that Brady requires disclosure of impeachment evidence. It also clarified the “materiality” prong of Brady. It said that a Brady violation occurs if the withheld evidence was “material” in the sense that there was a “reasonable probability” that its disclosure would have led to a different result in trial or sentencing. It explained that “reasonable probability,” meant “a probability sufficient to undermine confidence in the outcome.”
1995 – Kyles v. Whitley
Petitioner was convicted of first-degree murder and sentenced to death. Prior to trial, police had collected eyewitness statements containing physical descriptions of the attacker which were inconsistent with characteristics of the petitioner. These statements were not disclosed to the defense. Post-trial petitioner argued that this evidence had been suppressed in violation of Brady v. Maryland. The U.S. Supreme Court agreed. It imposed an affirmative duty on prosecutors to become aware of and disclose any favorable evidence held by others acting on the government’s behalf, including the police. The Court also clarified the materiality standard. It said that a defendant is not required to show that had the withheld evidence been disclosed, more likely than not he would have been acquitted. It reiterated that instead, a defendant need only show that the undisclosed evidence “undermines confidence” in the trial outcome.
2004 – Banks v. Dretke
Petitioner was convicted of murder and sentenced to death. The state represented that it had disclosed all Brady material, but it nevertheless failed to disclose the fact that a key witness was a paid government informant and that another witness’s testimony had been coached. Furthermore, prosecutors failed to correct the record when these witnesses testified falsely. Petitioner sought relief because of the apparent Brady violation but lost in the U.S. Court of Appeals for the 5th Circuit. The U.S. Supreme Court held that the lower court had erred in dismissing Petitioner’s Brady claim. It placed the onus for Brady compliance clearly on prosecutors. It said defendants need not “scavenge for hints of undisclosed Bradymaterial” and “[a] rule . . . declaring ‘prosecutor may hide, defendant must seek’ is not tenable.” The Court also reiterated the holding in Kyles v. Whitley: “the materiality standard for Brady claims is met when ‘the favorable evidence could reasonably be taken to… undermine confidence in the verdict.'” When police or prosecutors conceal exculpatory material in the state’s possession, it is incumbent on the state to set the record straight.