Also known as: exculpatory evidence · impeachment evidence · Brady material · Giglio evidence
Written by attorneys · grounded in primary & secondary sources — see below
Evidence favorable to the accused that tends to negate guilt or mitigate punishment or that undermines the credibility of prosecution witnesses. Due process requires the prosecution to disclose such material evidence to the defense upon request or otherwise. Suppression of material evidence of this type, whether intentional or inadvertent, requires reversal if there is a reasonable probability that disclosure would have produced a different result.
An alien detained as an enemy combatant learns after his military commission that new documents show he was not present at the alleged attack site. He petitions for habeas review and seeks to introduce those documents to contest the factual basis for his indefinite detention. The reviewing court must permit the introduction because the substitute process must allow challenges based on exculpatory evidence discovered after the commission proceedings.
Edward Everett is charged with robbery. The prosecution possesses a statement from the sole eyewitness admitting uncertainty about the perpetrator's identity but does not turn it over. Everett is convicted. On appeal the court reverses because the statement was material exculpatory evidence that the prosecution was required to disclose.
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Emma Erickson is on trial for assault. She seeks to introduce a reliable out-of-court statement from a now-unavailable declarant that another person committed the assault. The trial court excludes the statement under the hearsay rule. The appellate court reverses because exclusion of this critical exculpatory evidence deprived Erickson of a fair trial.
Evelyn Ellison testifies for the prosecution against Esme Ellington. Defense counsel seeks to show that Ellison belongs to an organization whose tenets require members to lie for fellow members. The trial court permits the cross-examination because evidence of bias is always relevant and admissible to impeach a witness.
Emmett Egan moves to exclude evidence of his prior conviction. The court denies the motion. Egan then introduces the conviction on direct examination to reduce its impact. On appeal he may not challenge the denial because introducing the impeachment evidence himself forfeits review of the ruling.
Elise Everly gives a statement to police after receiving defective Miranda warnings. The statement is introduced at trial to impeach her testimony. The court permits the use because the statement, though obtained in violation of Miranda, may still serve as impeachment evidence.
No. The duty attaches upon request or otherwise whenever the prosecution knows of material evidence favorable to the accused.
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Evidence is material if there is a reasonable probability that disclosure would have produced a different result. This standard applies to both exculpatory and impeachment evidence.
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Yes. The disclosure obligation turns on the content of the information and its tendency to negate guilt, not on the procedural label attached to the file containing it.
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…quite simply "may not be put to any testimonial use whatever against [the defendant] in a criminal trial," including as impeachment evidence. New Jersey v. Portash , 440 U. S. 450, 459 (1979). See also Mincey v. Arizona , 437 U. S. 385, 397-398 (1978) (holding that while statements obtained in violation of Miranda may be…