At SimpleJustice blog (a blog worth following) there is a piece about Judge Kopf and a tweet which leads to a discussion of a prosecutors obligation to provide discovery to the defense.
Let me start with some basics and two cases that prosecutors and defense lawyers know (or should know) well. In Brady v. Maryland, the Supreme Court held that suppression by the prosecution of evidence favorable to an accused violates due process where the evidence is material either to guilt or to punishment, irrespective of the good faith or bad faith of the prosecution. Evidence is “material” if there is a reasonable probability that, had the evidence been disclosed to the defense, the result of the proceeding would have been different.
Relatedly, in Giglio v. United States, the Supreme Court held that prosecutors must disclose to the defense any “understanding or agreement as to a future prosecution” that the government has made with a material witness. That notion has been expanded to requiring the production of impeachment information of a material character. Specifically, this is thought of as information that either casts a substantial doubt upon the accuracy of any evidence—including witness testimony—the prosecutor intends to rely on to prove an element of any crime charged, or might have a significant bearing on the admissibility of prosecution evidence.