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 1963 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. In practice this doctrine has often proved difficult to enforce. Some states have established their own laws to try to strengthen enforcement against prosecutorial misconduct in this area. Definition of the Brady rule The Brady doctrine is a pretrial discovery rule that was established by the United States Supreme Court in Brady v. Maryland (1963). The rule requires that the prosecution must turn over all exculpatory evidence to the defendant in a criminal case. Exculpatory evidence is evidence that might exonerate the defendant. Examples Examples include the following: 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 inform the prosecutor's office of anything that tends to prove the innocence of the defendant. Not all exculpatory evidence is required to be disclosed by Brady and its progeny; only evidence that is "material to guilt or punishment" must be disclosed because its disclosure would create a reasonable probability of changing the outcome of the proceeding. The prosecutor is not obligated to personally review police files in search of exculpatory information when the defendant asks for it, but to allow the defense reasonable access. The Supreme Court observed in Strickler v. Greene, "Thus the term 'Brady violation' is sometimes used to refer to any breach of the broad obligation to disclose exculpatory evidence – that is, to any suppression of so-called 'Brady material' – although strictly speaking, there is never a real 'Brady violation' unless the nondisclosure was