What’s the Difference Between a Jury and a Grand Jury?

The two types of juries in the American justice system are trial juries and grand juries. Both serve different purposes, though citizens can be called for “jury duty” in either.

A grand jury indicts someone at the beginning of a criminal case, and a trial jury decides someone’s guilt (and in some states, punishment) after a criminal trial finishes. A trial jury may also be convened in civil matters to determine which side will win and the judgement either will receive. 

Americans can get called for either jury through a random selection that uses a list of registered voters and other public records, such as driver’s license registrations. 

Jury duty requires one to be a U.S. citizen and legal resident of the state or district where the jury is being convened. If someone fails to show up once, they will likely be given a warning and called again. They could also be fined or held in contempt. 

For grand juries, when an American receives a summons, they have to fill out a brief survey to ensure they qualify and then follow the instructions on when and where to report. A citizen will also receive a questionnaire if they're called for trial jury duty. If they are summoned to court and have their name called, they’ll have to answer more questions asked by either the defense or state attorney. They will then decide whether to strike or sit you; people with strong personal opinions about the case are likely to be dismissed. 

Felony convictions will also disqualify someone from being called, and a juror must be able to speak English and have the mental and physical capabilities to sit through a trial and make a decision.

Grand juries, in most cases, are convened before someone is indicted in a criminal case. It’s up to the jurors and the district attorney to determine if the jurisdiction has enough evidence to move forward with a trial. Sometimes, district attorneys will decide to skip grand juries and complete the process though a preliminary hearing in front of a judge. 

How grand juries operate varies by jurisdiction, but most consist of 16 to 23 people. Everything about grand jury proceedings—such as records, transcripts of the jury presentations, and names of jurors—are kept secret. Some jurors could have grand jury duty for many weeks or months.

When a grand jury is convinced in a criminal matter, the prosecutor decides what evidence to present. The defense team is not present during a grand jury hearing.

Hearings are often more informal than those for trial juries, and grand juries can ask questions.

In some states, like Nebraska, grand juries are convened after someone dies in police custody or while being arrested. Jurors investigate if any criminal charges should be filed. If the answer is no, those transcripts become public record in Nebraska. 

Though the proceedings are held in private, judges can decide to later release grand jury cases, which was decided in the police shooting of Breonna Taylor in Kentucky. A grand jury declined to indict the officers who killed her, and the Kentucky attorney general did not pursue charges after the jury’s decision, which resulted in protests and calls for the grand jury proceedings to be released. A judge ruled to release 15 hours of audio of the proceedings after a juror filed a motion for access. Convictions against the officers were later secured in federal court.

Trial juries, which consist of six to 12 people, are part of criminal and civil trials and occur after a grand jury makes its indictment. 

Trials are open to the public and allow media coverage; the judge gets to decide what that entails. Some judges allow multiple cameras to be in a courtroom, while others designate a “pool photographer” to take all of the footage and share with other outlets. 

After hearing evidence in a trial, jurors are then removed from a courtroom to discuss the verdict in private. In these cases, the verdicts must be unanimous, or a judge may declare a mistrial. Juries must find guilt beyond a reasonable doubt.

Unlike grand juries, those in trial juries are not allowed to openly ask questions during proceedings. However, during deliberations, juries can ask clarifying questions of the judge, who then decides whether to answer.

Some notable jury trials involved the acquittals of O.J. Simpson—who was tried in the murder of his ex-wife, Nicole Brown Simpson, and her friend, Ron Goldman—and Casey Anthony, who was tried for killing her 2-year-old daughter. A juror in Anthony’s case later told reporters that the group disliked Anthony, but they didn’t believe prosecutors proved beyond a reasonable doubt that she killed Caylee.