In United States v. Agurs, 427 U.S. 97 (1976) it became clear that a defendant's failure to request favorable evidence did not leave the Government free of all obligation. There, the Court distinguished three situations in which a Brady claim might arise: first, where previously undisclosed evidence revealed that the prosecution introduced trial testimony that it knew or should have known was perjured; second, where the Government failed to accede to a defense request for disclosure of some specific kind of exculpatory evidence; and third, where the Government failed to volunteer exculpatory evidence never requested, or requested only in a general way. The Court found a duty on the part of the Government even in this last situation, though only when suppression of the evidence would be "of sufficient significance to result in the denial of the defendant's right to a fair trial."