Also known as: impeachment informations · impeachment evidence · Giglio material
Written by attorneys · grounded in primary & secondary sources — see below
Evidence offered to undermine a witness's credibility at trial. Such evidence includes proof of bias, prior convictions, or inconsistent statements and must be disclosed when material to guilt or punishment under due process standards.
Iris Irons testified for the prosecution in a fraud trial. Defense counsel cross-examined her about membership in a professional group whose internal guidelines encouraged members to shield clients from liability findings. The trial court allowed the questions because evidence of bias is always relevant to credibility.
Isabella Ingram faced trial on drug charges. After the court denied her motion to exclude a prior conviction, she elicited the conviction herself on direct examination to reduce its impact. On appeal she could not challenge the ruling because she had introduced the evidence preemptively.
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Isaiah Ishikawa negotiated a plea agreement in a conspiracy case. Prosecutors withheld information that could have impeached a key government witness. The court upheld the plea because the Constitution does not require disclosure of impeachment information before a defendant enters a guilty plea.
Ingrid Innes and co-defendants sought disclosure of promises made to government witnesses. The prosecution acknowledged its duty to produce impeachment information but limited production to materials that were genuinely exculpatory.
Idris Ives called a defense witness whose testimony conflicted with earlier statements obtained by police. The prosecution sought to use illegally obtained evidence to impeach that witness. The court refused because the impeachment exception does not extend to all defense witnesses.
Ines Ibarra was convicted after the prosecution withheld evidence that could have impeached its main witness. On appeal the court reversed because there was a reasonable probability that disclosure would have produced a different result.
The Constitution does not require disclosure of impeachment information before a plea agreement. Failure to provide such evidence does not render the plea involuntary.
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Impeachment evidence is material if there is a reasonable probability that its disclosure would have produced a different result at trial.
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Evidence of bias is always relevant and admissible. A witness may be impeached by showing membership in an organization whose tenets encourage members to lie or commit perjury on behalf of fellow members.
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Yes. When a defendant preemptively introduces a prior conviction on direct to lessen the sting of anticipated impeachment, the defendant may not later claim on appeal that admission was error.
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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…