A grand jury is a type of jury, comprised of citizens who are presented with evidence from a state or federal prosecutor (District Attorney or United States Attorney) to determine whether there is probable cause to believe a person committed a crime and should be put on trial. If the grand jury determines there is enough evidence, an indictment will be issued against the defendant. This is known as a “true bill,” and the grand jury is said to have “returned a true bill.” If the grand jury does not believe there is sufficient evidence the accused committed a crime and should be put on trial, it is said to return a “no true bill" or "no bill."

The United States Constitution does not require states to use a grand jury to bring criminal charges against a person—but many states do use grand juries, and some states are required by their state constitution or statutes to use a grand jury to secure an indictment for any felony criminal offense. And the U.S. Supreme Court has interpreted the Constitution to require the federal government to use grand juries for all felony crimes.

Grand jury proceedings are not open to the public and accused persons and their attorneys do not have the right to appear before the grand jury, or to be informed of the proceedings. Witnesses subpoenaed by a grand jury do not have the right to have their attorney present during their testimony. The grand jury proceedings are generally transcribed by a court reporter, but the record is sealed.

Federal grand juries generally consist of 16-23 persons who serve or work on the grand jury for a few days each month for approximately one year—after which a new grand jury is selected by the Federal District Court. At least 12 jurors must agree to return a true bill for indictment of the accused person.

Procedures for the use of grand juries in the state court system vary from state to state and are generally governed by the state’s constitution, and statutes that are often located in the penal or criminal code, the code of criminal procedure, or the government code.

In Minnesota, grand juries are used in accordance with both state statutes and the Minnesota Rules of Criminal Procedure. The state employs grand juries primarily for felony cases, and their use is discretionary for the prosecution, except in cases involving first-degree murder where an indictment by a grand jury is required. A grand jury in Minnesota typically consists of 16 to 23 members, similar to federal grand juries, and at least 12 jurors must concur to issue an indictment, known as a 'true bill.' If the grand jury finds insufficient evidence to indict, they return a 'no bill.' Grand jury proceedings in Minnesota are secret; the accused and their attorneys do not have the right to be present, and witnesses cannot have their attorneys with them during testimony. The proceedings are recorded and kept sealed, except under certain circumstances where the transcript may be disclosed. The use of grand juries in Minnesota is governed by the state's rules and statutes, which provide the framework for their operation, including the selection of jurors, the duration of service, and the procedures to be followed during the grand jury process.