Final answer:
A grand jury is a legal body that determines whether there is enough evidence to indict someone for a felony, leading to a trial. While the Fifth Amendment mandates its use in federal cases, states are not required to use them. Grand jury proceedings are secret and focus on establishing probable cause rather than guilt.
Step-by-step explanation:
A grand jury is a body of people who are chosen to sit for a specified period of time and who, in ex parte proceedings, decide whether there's sufficient evidence to charge someone with a crime and then to prosecute. According to the Fifth Amendment, a person can only be tried in federal court for a felony after a grand jury issues an indictment, which is a formal accusation that a person has committed a crime. The Supreme Court has determined that states are not required to use grand juries, as long as they employ an equally fair process.
The functions of a grand jury include the review of evidence presented by the prosecutors to determine whether there is probable cause to believe a crime has been committed. This process is typically done in secret, and the grand jury does not determine guilt or innocence but merely whether to indict the accused, leading to a trial. This constitutional requirement, however, has exceptions such as military personnel in service during war or public danger, who are not entitled to a grand jury. Instead, other procedures, such as preliminary hearings before a judge, are used to decide whether a trial should proceed.