Two of the most important cases in criminal defense aren’t about a specific crime at all — they’re about what the government owes a defendant during discovery. Brady and Giglio establish constitutional obligations for prosecutors to turn over certain evidence, regardless of whether the defense even asks for it.
Brady v. Maryland: Exculpatory Evidence
In Brady v. Maryland (1963), the U.S. Supreme Court held that the prosecution violates due process when it suppresses evidence favorable to a defendant that is material to guilt or punishment. In plain terms: if the government has evidence that could help the defense — evidence pointing to innocence, undermining the State’s theory, or supporting a lesser charge — it has to hand it over.
This is a constitutional duty, not a discretionary courtesy. It doesn’t matter whether the defense specifically requested the material. The obligation exists automatically, and it applies to the entire "prosecution team" — not just the prosecutor’s own file, but police reports, lab results, and other information gathered by law enforcement agencies involved in the investigation.
Giglio v. United States: Impeachment Evidence
Giglio v. United States (1972) extended Brady to a specific and very common category of evidence: information that could be used to impeach the credibility of a State’s witness. This includes things like:
- Deals, plea agreements, or promises of leniency made to a witness in exchange for testimony
- A witness’s prior inconsistent statements
- A witness’s criminal history
- Any bias or motive the witness might have to help the prosecution
If a key witness — particularly a cooperating witness or informant — has something to gain by testifying against a defendant, that fact belongs in front of the jury. Giglio material lets the defense challenge not just what a witness says, but why they’re saying it.
Why This Combination Matters
Brady and Giglio together mean the government isn’t just an adversary presenting its best case — it also carries an affirmative constitutional duty to disclose evidence that helps the defense, whether that evidence points toward innocence or simply toward reasons to doubt a witness. Failing to turn over this kind of material isn’t just an oversight; when it’s significant enough, it can be grounds to challenge a conviction after the fact.
For a defense attorney, this means discovery isn’t a passive process of waiting to see what gets handed over. It means asking pointed questions: What deals were offered to cooperating witnesses? Were there inconsistent statements in the investigation? Is there evidence in the file that doesn’t fit the State’s theory of the case? Brady and Giglio give the defense the legal footing to demand answers to exactly those questions.
This post is for general information and does not constitute legal advice. If you have questions about discovery in your case, contact our office to discuss your specific situation.