Exculpatory Evidence
Exculpatory evidence is the Brady obligation, and the direction of the duty is the first thing to fix in your mind.
20. Exculpatory Evidence
The prosecution has a constitutional Due Process obligation to disclose exculpatory evidence to the defense. “Exculpatory” evidence includes any evidence that is material to either guilt or punishment; it includes evidence that would help impeach a government witness.
- The prosecution’s obligation applies to evidence that is material to either guilt or punishment, including impeachment evidence.
- Courts will overturn a conviction obtained in violation of this obligation if there was “a reasonable probability that, had the evidence been disclosed to the defense, the result of the proceeding would have been different.”
- Courts may overturn a conviction obtained in violation of this principle even if the prosecutor acted in good faith or the failure to disclose was inadvertent. The critical question is prejudice to the defendant, not the prosecutor’s mental state.
Exculpatory evidence is the Brady obligation: the duty runs from the prosecution to the defense to hand over evidence favorable to the accused and material to either guilt or punishment. The question is always prejudice to the defendant, never the prosecutor's intentions.
The word material is doing real work here, but so is the word exculpatory, because that category is broader than students expect. It is not limited to evidence that directly shows the defendant did not do it. It expressly includes impeachment evidence, meaning evidence that would help the defense undercut the credibility of a government witness. If the state has a deal with its star witness, or information showing that witness lied before, that is exculpatory and must be disclosed.
The remedy side has its own precise standard. A court will overturn a conviction only when there is a reasonable probability that, had the evidence been disclosed, the result of the proceeding would have been different. That is not certainty, and it is not a simple more-likely-than-not weighing of the verdict. It is a reasonable probability of a different result, which is enough to undermine confidence in the outcome.
The most heavily tested point is the prosecutor's state of mind, and the rule is blunt: it does not matter. A conviction can be overturned even if the prosecutor acted in complete good faith, and even if the failure to turn the evidence over was an honest oversight. Treating good faith as a defense is the trap this concept is built to catch.
"Prosecution discloses; good faith is no excuse."
The duty runs prosecution to defense, and it covers anything material to guilt or punishment, including impeachment of a government witness.
Two facts that never save the conviction from reversal: "the prosecutor acted in good faith" and "the nondisclosure was inadvertent." The remedy test is a reasonable probability that disclosure would have changed the result, not certainty and not a flat preponderance.
prosecution must disclose material exculpatory and impeachment evidence; prejudice controls, not the prosecutor's mental state.
A prosecutor tries a robbery case. The conviction rests largely on the testimony of a single eyewitness. After trial, the defense learns that the prosecution's file contained a signed cooperation agreement promising that same eyewitness leniency on her own pending charges in exchange for testifying, and the agreement was never turned over. The prosecutor swears she simply overlooked the document in a large file and never meant to hide it. The defendant moves to overturn the conviction.
The conviction should be overturned. Flip only the materiality: if the undisclosed item were trivial and the witness's account were corroborated by overwhelming independent proof, the reasonable-probability standard might not be met, and the conviction could stand.
An answer that lets the conviction stand because the prosecutor "acted in good faith" or the failure to disclose was "inadvertent" or "an honest oversight."
A conviction may be overturned even if the prosecutor acted in good faith or the nondisclosure was inadvertent; the critical question is prejudice to the defendant, not the prosecutor's mental state.An answer that misstates the remedy standard, demanding the defendant prove the evidence "certainly" would have changed the outcome or a flat preponderance that the verdict was wrong.
The standard is a reasonable probability that, had the evidence been disclosed, the result of the proceeding would have been different, which is less than certainty.An answer claiming impeachment evidence is not covered, or that only guilt-related evidence (not punishment) must be disclosed.
The obligation reaches evidence material to either guilt or punishment and expressly includes evidence that would help impeach a government witness.An answer that flips the direction of the duty onto the defense, or attaches it to whoever possesses the evidence, rather than to the prosecution.
The Due Process obligation to disclose exculpatory evidence runs from the prosecution to the defense; it is the prosecution's duty.the stem hands you a criminal trial where the prosecution had something favorable to the accused in its file and did not turn it over.
Watch for the classic dress-up facts: a cooperation deal or prior-lie information about a key government witness (that is impeachment evidence, squarely covered), and a prosecutor who insists the omission was an honest oversight or made in good faith (true but irrelevant).
The instant you see undisclosed favorable evidence, run the Brady check: was the evidence material to guilt or punishment, including impeachment of a government witness, and is there a reasonable probability that disclosure would have changed the result?
If yes, the conviction is vulnerable, and every answer resting on the prosecutor's good faith or honest mistake is a distractor.
If the evidence was trivial and the result was not reasonably in doubt, the reasonable-probability standard is not met.
A defendant was convicted of armed robbery largely on the testimony of one eyewitness. After the verdict, the defense discovered that the prosecution's file had contained a written agreement promising that eyewitness a reduced sentence on her own unrelated charges in exchange for her testimony, and that the agreement was never turned over. The prosecutor explained, credibly, that she had simply missed the document in a thick file and had no intent to conceal anything. The defendant moved to overturn the conviction.
Is the defendant's argument that his Due Process rights were violated likely to succeed?
Before trial, the prosecution possessed a lab report tending to show the defendant was not the source of physical evidence at the scene, but it never gave the report to the defense. The defendant was convicted. On appeal, the prosecution conceded the report was favorable to the defense and material but argued that the conviction should stand because the lead prosecutor had never personally seen the report and harbored no intent to hide anything from the defense.
How should the appellate court treat the prosecution's good-faith argument?
A defendant convicted at trial later learned that the prosecution had failed to disclose a witness statement favorable to the defense. Seeking to overturn the conviction, the defendant asked the court what he had to show about the effect of the nondisclosure on his trial.
What must the defendant establish to have the conviction overturned?
During a criminal trial, defense counsel realized that the prosecution likely held a memo casting doubt on the reliability of the prosecution's main witness, but the prosecution had not produced it. The defense asked the trial judge to direct disclosure, and the prosecution responded that the constitutional disclosure duty actually obligated the defense to come forward with such material, not the prosecution.
Which party bears the constitutional obligation to disclose this evidence?
A defendant was convicted, and the prosecution acknowledged it had not disclosed a favorable document in its file. The trial record showed the undisclosed document was minor and that the verdict rested on overwhelming, independent evidence of guilt, so that disclosing the document would not have created any reasonable probability of a different result. The defendant nonetheless argued the conviction had to be overturned simply because the prosecution failed to disclose favorable evidence.
Is the defendant likely to have the conviction overturned on these facts?