Brady disclosure consists of exculpatory or impeaching information and evidence that is material to the guilt or innocence or to the punishment of a defendant. The term comes from the U.S. Supreme Court case, Brady v. Maryland, in which the Supreme Court ruled that suppression by the prosecution of evidence favorable to a defendant who has requested it violates due process. Following Brady, the prosecutor must disclose evidence or information that would prove the innocence of the defendant or would enable the defense to more effectively impeach the credibility of government witnesses. Evidence that would serve to reduce the defendant's sentence must also be disclosed by the prosecution.
The prosecutor must disclose an agreement not to prosecute a witness in exchange for the witness's testimony.
The prosecutor must disclose leniency (or preferential treatment) agreements made with witnesses in exchange for testimony.
The prosecutor must disclose exculpatory evidence known only to the police. That is, the prosecutor has a duty to reach out to the police and establish regular procedures by which the police must inform him of anything that tends to prove the innocence of the defendant. However, the prosecutor is not obligated to personally review police files in search of exculpatory information when the defendant asks for it.
The prosecutor must disclose arrest photographs of the defendant when those photos do not match the victim's description.
Some state systems have expansively defined Brady material to include many other items, including for example any documents which might reflect negatively on a witness's credibility.
Police officers who have been dishonest are sometimes referred to as "Brady cops." Because of the Brady ruling, prosecutors are required to notify defendants and their attorneys whenever a law enforcement official involved in their case has a sustained record for knowingly lying in an official capacity.