The allowable scope of discovery by defendants is much more limited in criminal cases. This is rationalized by the high burden of proof that the prosecutor must meet: even if defendants do nothing in their defense, the state will still lose unless it convinces the jury of the defendant’s guilt beyond a reasonable doubt. Under federal law, the defendant need not provide any testimony to the prosecutor unless the defendant wants to raise a defense of mental incapacity, alibi, or governmental authority. The courts and legislatures are also concerned with the reluctance of witnesses to testify if they fear retaliation. There is also the possibility that if defendants in some cases know before about adverse testimony before trial, they would attempt to suborn perjury—get the witnesses to lie or find other persons to lie to contradict them. In extreme cases, the federal law provides for preventive detention of the defendant or of the witnesses to prevent witness intimidation or murder. [United States v. Salerno, 481 U.S. 739 (1987) .]

Although the defendant does not have a right to all the information that the government holds, the defendant does have a constitutional right to favorable evidence that the government holds. [Brady v. Maryland, 373 U.S. 83 (1963) ] The difficulty is for the defendant to figure out how to ask for specific evidence that meets this test when the defendant does not know what evidence the government is holding. The defendant’s attorney must craft a “Brady request” that forces the government to either turn over the evidence or risk having their case reversed on appeal if the evidence comes out at trial or even posttrial. For reversal, the defendant must show that he or she did not have other notice of the information. There is no violation “where a defendant knew or should have known the essential facts permitting him to take advantage of any exculpatory information, or where the evidence is available from another source.” [United States v. Clark, 928 F.2d 733, 738 (6th Cir. 1991) .] The defendant must also show that the evidence that was withheld is “material,” in that there is a reasonable probability that it would have affected the result of the trial. [United States v. Bagley, 473 U.S. 667, 682 (1985) .]

The defendant is entitled to the records of certain of his or her own statements made to the police and to recorded statements made by witnesses who testify. These are generally not provided before the trial, but only at the time the witnesses testify. The government is permitted to give the defendant more information, and the defendant may petition the judge to order the government to produce other information. The government has an incentive to provide additional information because it reduces the defendant’s grounds for appeal based on withholding exculpatory evidence. This is most important in cases involving the death penalty where the postconviction review is the most thorough and the defendant gets the greatest benefit of the doubt as to the importance of the evidence.