Giglio v. United States, 405 U.S. 150 (1972), is a United States Supreme Court case in which the Court held that the prosecution's failure to inform the jury that a witness had been promised not to be prosecuted in exchange for his testimony was a failure to fulfill the duty to present all material evidence to the jury, and constituted a violation of due process, requiring a new trial.

The case extended the Court's holding in Brady v. Maryland,[2] requiring such agreements to be disclosed to defense counsel.

An affidavit indicated that Assistant U.S. Attorney DiPaola struck a deal with Taliento, promising that he would not be prosecuted for the crime if he testified against Giglio.

The Supreme Court granted certiorari to determine whether the evidence that was not disclosed required a new trial under the due process criteria that had been enunciated in Napue v. Illinois[7] and Brady v.

[5] In Giglio's case, the Court found that neither DiPaola's authority nor his failure to inform his superior Hoey or his associate Golden was controlling.