In 1963, the U.S. Supreme Court decided Brady v. Maryland and established one of the most important rules in American criminal law: prosecutors must turn over any evidence that is favorable to the defendant and material to guilt or punishment. Failure to do so violates the Constitution.
That rule - known as the Brady rule - sounds simple. In practice, it gets violated regularly, and those violations have sent innocent people to prison for decades.
What Brady Actually Requires
The Brady rule applies to evidence that is:
Favorable to the defendant. This includes evidence that tends to show the defendant didn't commit the crime (exculpatory evidence) and evidence that could be used to challenge the credibility of prosecution witnesses (impeachment evidence). Both categories are covered.
Material. Evidence is material if there is a reasonable probability that the result of the trial would have been different had it been disclosed. This doesn't mean the defendant would have definitely been acquitted - just that the outcome might have been different.
In the prosecution's possession. This includes evidence in the possession of the police department, not just the prosecutor's file. Prosecutors have a duty to learn of favorable evidence known to others acting on the government's behalf.
What Gets Withheld - and Why
Brady violations range from negligent oversight to deliberate concealment. In some cases, a detective's notes revealing an alternate suspect were never turned over because no one thought to include them. In others, prosecutors actively hid evidence that they knew would undermine their case.
Common categories of withheld evidence include: witness statements that contradict the prosecution's theory of the case. Information about deals made with informants or cooperating witnesses - someone who was given a plea deal in exchange for testimony, where the deal was never disclosed to the defense. Police reports documenting witness descriptions that don't match the defendant. Laboratory reports showing inconclusive or contradictory forensic results. Criminal histories of prosecution witnesses that could have been used to challenge their credibility.
The National Registry of Exonerations has found that official misconduct - which includes Brady violations - is a contributing factor in roughly half of all documented wrongful convictions. That is not a small number.
How Brady Violations Are Discovered After Conviction
This is the hard part. Evidence that was withheld is, by definition, evidence that the defense never saw. Discovering it after conviction usually happens in one of a few ways.
Someone talks. A witness comes forward and says they told the police something that was never in the official report. A former detective or prosecutor, years later, reveals something that was buried. A co-defendant, after serving their sentence, discloses a deal they were offered that was never made public.
Files are released. Cold case reviews, public records requests, or civil litigation sometimes surface documents that were never turned over during the original prosecution. In some cities, journalism investigations have discovered entire caches of police reports that were withheld in multiple cases.
Patterns emerge. When a prosecutor or detective is implicated in one case of misconduct, it often triggers review of other cases they were involved in. Some of the largest groups of exonerations in history have come from investigations into a single corrupt officer or prosecutor whose conduct was finally exposed.
Raising a Brady Claim After Conviction
A Brady violation can be raised in a post-conviction petition - but with complications. Courts generally require that the defendant didn't know about the evidence and couldn't have discovered it with reasonable diligence. And the evidence has to be material enough that there's a reasonable probability the verdict would have been different.
The timeliness issue is also significant. If new evidence of a Brady violation emerges, it generally needs to be raised promptly - sitting on it weakens the legal argument that it's genuinely new information.
Brady claims are most powerful when combined with other evidence. A withheld witness statement is stronger when it corroborates a recantation, or when it points to a specific alternate suspect. A withheld deal with an informant is stronger when there are other reasons to question the informant's testimony.
If you believe evidence was withheld in a case you're fighting, document everything you know and bring it to a post-conviction attorney or innocence organization as specifically as possible. "I think the prosecutor hid things" is not a Brady claim. "Detective X wrote a report on October 14th describing a suspect who doesn't match my loved one, and that report is not in the discovery file" is.
Use our state resources directory to find organizations that can evaluate Brady claims in your state.