It is the duty of the Grand Jury to hear the evidence against a person accused of committing a crime (as opposed to a disorderly persons offense, which does not require Grand Jury review). The Grand Jury must then decide if there is sufficient evidence to formally charge, or "indict", the accused. After listening to witnesses, viewing physical evidence, if any, and discussing the case, the Grand Jury can vote:

• a True Bill, which formally charges the accused,
• a No Bill, which dismisses the charges, or
• a No Bill with Remand, which refers the case back to the municipal court on lesser charges

The Grand Jury is an independent body consisting of 23 members of the community, with 12 affirmative votes needed in order to return an indictment. The proceedings are private, but a transcript is made for use by the court, the Prosecutor’s Office and the defendant. The defendant may or may not testify before the Grand Jury.

It is the responsibility of the assistant prosecutors assigned to the Grand Jury Section to review the cases and then present the witnesses and evidence to the jury. The assistant prosecutors must also impartially explain the law to the Grand Jury on the charges facing the defendant. If the defendant is indicted, the prosecutors prepare and sign the indictment, a written document outlining the charges that is filed with the court and provided to the defendant.

Until 1999, Grand Jurors in Essex County sat for five weeks, three days per week. Their hours of service were from approximately 9:00 a.m. until 1:00 p.m. Approximately, fifteen cases per day were scheduled. Now, grand jurors sit one day per week for fifteen weeks. They now hear approximately twenty-five to thirty cases per day during the hours from 9:00 a.m. until 4:00 p.m. In order to facilitate case scheduling under the new system, while respecting the wishes of most Grand Jurors not to be held past the 4 p.m. closing time (given domestic and child care responsibilities), the Essex County Prosecutor's Office is developing a “weighting” system to give the Grand Jury Clerks an idea of the complexity of a given presentation, and permit them to designate an appropriate number of cases to be heard, given available time.

In 2005, the Grand Jury Section presented 4,576 cases. The Grand Jury voted a True Bill in 4,268 cases; a No Bill in 297 cases; and remanded 11 cases back to the municipal court.