What is a grand jury? When is a grand jury called, and what procedures does it follow?

A grand jury is a group of citizens called to decide whether there is probable cause to believe that the defendant committed the crime with which he or she is charged and therefore should go to trial. The federal government and about half of the states require a grand jury, and not the prosecutor, to make the decision as to whether a case should go to trial in felony cases. In other words, a grand jury's indictment is an alternative to a prosecutor's information to initiate the criminal litigation process. Even in cases in which grand jury review is not required, the prosecutor may call a grand jury to evaluate the evidence against a suspect, which will indicate to the prosecutor the relative strength or weakness of the case.
The grand jury sits in closed session and hears only evidence presented by the prosecutor-the defendant cannot present evidence at this hearing. Normally, the defendant and the defendant's attorney are not even allowed to attend grand jury proceedings-although in some cases, the defendant may be required to testify. The prosecutor presents to the grand jury whatever evidence the state has against the defendant, including photographs, documents, tangible objects, test results, the testimony of witnesses, and other items. If the grand jury finds that probable cause exists, it issues an indictment against the defendant called a true bill. Over 97 percent of the cases that prosecutors bring to grand juries result in an indictment. The indictment is filed with the trial court and becomes the formal charge against the defendant.