The Brady Rule, named for Brady v. Maryland, 373 U.S. 83 (1963), requires prosecutors to disclose materially exculpatory evidence in the government's possession to the defense. "Brady material" or evidence the prosecutor is required to disclose under this rule includes any evidence favorable to the accused-- evidence that goes towards negating a defendant's guilt, that would reduce a defendant's potential sentence, or evidence going to the credibility of a witness.
If the prosecution does not disclose material exculpatory evidence under this rule, and prejudice has ensued, the evidence will be suppressed. The evidence will be suppressed regardless of whether the prosecutor knew the evidence was in his or her possession, or whether or not the prosecutor intentionally or inadvertently withheld the evidence from the defense. The defendant bears the burden of proving that the undisclosed evidence was material, and the defendant must show that there is a reasonable probability that there would be a difference in the outcome of the trial had the evidence been disclosed by the prosecutor.