In Brady v. Maryland, the Supreme Court set the basic outlines of what has become known as the “Brady doctrine.” The government, according to this principle, has a general duty to disclose information in its possession that is favorable to the defense. The concept, at least in its rough outlines, is largely noncontroversial. In other words, almost everyone would agree that the government has such a duty. The application of the Brady doctrine, however, is both controversial and dependent on perceptions and prejudices of the individual interpreter.
A requirement of what the Court has called “materiality” is at the heart of the doctrine. But the significance of this requirement is different from the meaning of materiality in other contexts. Loosely, materiality as an element of a Brady violation is intended to correspond to a kind of importance. The idea is that information not at all likely to affect the outcome at trial is not the kind of information with which Brady is concerned. Just as the Brady doctrine is intuitively appealing, so is the materiality requirement because information that is unimportant does not seem an appropriate subject of a constitutional mandate.