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.

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 has developed 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 2008, 4,217 cases were presented to the Grand Jury with True Bills being returned for 3,359 cases, with an additional 24 cases referred to the Remand Court or municipal courts for resolution. In 2009, 3,953 cases were presented to the Grand Jury with True Bills being returned for 3,306 cases, with an additional 24 cases referred to the Remand Court or municipal courts for resolution.