Presenting the prosecutor's case. The prosecutor's grand jury presentation ordinarily begins with an explanation of a proposed indictment and a summary of the evidence that will be offered to support it. The evidence is then presented through the testimony of witnesses or the introduction of documents. In many jurisdictions (but not the federal), the prosecution has an obligation to produce, in addition to supporting evidence, any further evidence that it knows to be exculpatory. Thus, if a lineup produced conflicting eyewitness identifications, the prosecutor must make the jury aware of that conflict and not simply present the one eyewitness who identified the accused. The prosecutor's disclosure obligation is limited, however, to evidence obviously exculpatory and material. The prosecutor need not assume the role of a defense counsel and introduce all the evidence that a defense counsel might have wished to offer.
Although grand jury proceedings are secret, persons often are informed—for example, after being arrested—that charges against them will be presented to the grand jury. The grand jury proceeding is not an adversary proceeding, however, and those persons have no right to present their own evidence to that body. The potential defendant may request the opportunity to testify before the grand jury, but conventional wisdom deems that a risky tactic, as it subjects the potential defendant to cross-examination by the prosecution in a setting in which neither counsel (in most jurisdictions) nor the judge (in all jurisdictions) is present. Should such a request be presented, most jurisdictions hold that the grand jury can reject or grant the request at its discretion. Several states, however, give the potential defendant a right to testify if he so chooses, and they may permit him to be accompanied by counsel.
Evidentiary restrictions. All jurisdictions require that the testimonial privileges of a witness be recognized in grand jury proceedings. Beyond that, there is considerable variation in the applicability of rules of evidence that would govern at trial. A small group make these evidentiary rules fully applicable. Among indictment jurisdictions, those that generally favor application of the rules of evidence will recognize one or more broad exceptions to the rules of evidence. Those exceptions typically are designed to remove the burden of testifying from persons whose testimony ordinarily would not present a significant credibility issue (e.g., forensic experts).
Most indictment jurisdictions, and many information jurisdictions, simply refuse to apply the rules of evidence (other than testimonial privileges) to grand jury proceedings. In these jurisdictions, prosecutors may use any type of evidence without regard to whether it could be used at trial. Thus, prosecutors need not have key witnesses themselves testify, but may simply introduce statements the witnesses gave to the police, even though those statements would be inadmissible hearsay at trial. In Costello v. United States, 350 U.S. 359 (1956), the Supreme Court held that the prosecutorial practice of relying entirely on hearsay did not violate the Fifth Amendment. The Court stressed that historically, the grand jury was a "body of laymen" whose "work was not hampered by rigid procedural rules" (350 U.S. 362).
Standard for indictment. In many states the grand jury is directed to indict only if the evidence before it establishes probable cause to believe that the accused committed the felony charged; in others, it is directed to indict "when all the evidence taken together, if unexplained or uncontradicted, would warrant a conviction of the defendant." The first standard is very much like that applied by a preliminary-hearing magistrate. The second is a somewhat more rigorous standard, being similar to the standard applied by a trial judge in ruling on a motion for directed acquittal. No matter which standard applies in the particular jurisdiction, the jurors need not be unanimous in their conclusion that it is met. At common law, a vote of a majority (twelve out of twenty-three jurors) was sufficient to indict. Many jurisdictions now permit smaller grand juries, but require a somewhat higher percentage of votes for indictment (for example, twelve out of sixteen).
In some jurisdictions, generally those applying the rules of evidence, a defendant may challenge an indictment as not supported by sufficient evidence. To sustain such a challenge, the court must find that the evidence before the grand jury, even if read in a light most favorable to the state, did not meet the applicable standard for indictment. Other jurisdictions refuse all challenges to the sufficiency of the evidence before the grand jury. They stand by the standard suggested in Costello, that "an indictment returned by a legally constituted and unbiased grand jury, . . . if valid on its face, is enough to call for a trial on the merits" (350 U.S. 363).
The debate. Few criminal justice issues have been the subject of such prolonged and heated debate as the comparative merits of prosecution by indictment and prosecution by information. Critics of prosecution by indictment tend to fall into two categories. First, there are those who see the screening grand jury as no more than a rubber stamp for the prosecutor. They point to various indictment jurisdictions in which grand juries have refused to indict in less than three percent of their cases. The legal structure of the grand jury, these critics argue, gives it only theoretical independence; in light of the prosecution's ready access to investigative resources, its legal expertise, and its close working relationships with the grand jurors, it is inevitable that the grand jurors will follow the prosecution's lead on whether the evidence is sufficient to proceed.
Supporters of grand jury screening offer a quite different reading of grand jury independence and the statistics on refusals to indict. They argue that a low rate of refusals to indict simply indicates that prosecutors, respecting independent grand jury review, have themselves eliminated the weaker cases. The success of grand jury screening, supporters note, is evidenced by the high percentage of indictments that produce convictions and the very small percentage that result in dismissals for want of substantial evidence (opponents respond that dismissals on the prosecutor's own motion and negotiated pleas to lesser offenses are more common, and they may cover flaws in grand jury screening). Reference is also made to the experience in jurisdictions in which prosecutors do not screen so carefully and in which grand juries have refused to indict in as many as 15 percent of their cases.
A second group of critics acknowledge that the grand jury has some value as a screening agency, but believe that preliminary hearing is a better screening procedure. They contend that an independent magistrate, an adversary proceeding, and an open hearing clearly make the preliminary hearing the more effective procedure for eliminating unwarranted prosecutions. Grand jury supporters respond that the grand jury is the better screening agency because its strength lies where screening is most needed—in those cases where special factors, such as the involvement of politics or racial animosity, will probably result in unjust accusations. Lay participation permits the grand jury to evaluate the prosecution's case in light of community notions of justice and fairness. Indeed, the grand jury has the recognized authority to "nullify" the law by refusing to indict, notwithstanding legally sufficient evidence.