The criminal justice system has two types of juries. You might hear about the trial jury often, but you likely only hear about the grand jury in very serious cases on the news. You might not realize how these differ, but knowing a bit about this can help you if you are involved in the criminal justice system.
The grand jury is used before you have a criminal charge placed against you. The purpose of this jury is to determine whether the prosecution has enough evidence to go to a criminal trial. This is determined by reviewing the prosecutor's case in an information hearing in which jurors can ask questions and find out what they need to know to make an informed decision.
Once the grand jury makes a decision, they will let the prosecutor know whether they feel the person should be indicted or not. If they choose to indict, they are saying that there is enough evidence to warrant charges.
The prosecutor will have to decide whether to follow the grand jury's recommendation. They do have the power to do the opposite, so they can issue charges without an indictment, or they can leave the case alone despite an indictment being issued.
The trial jury is the one that decides whether a person is guilty or not guilty of a criminal charge. They hear the case from each side during a formal hearing. Once they know this and receive instructions from the judge, they can deliberate and come to a decision. Unlike the grand jury, the trial jury's decision is final.
It is imperative that you work diligently on your defense against criminal charges. You don't need to go before the trial jury unprepared for the proceedings.