The Grand Jury performs an important function under our Constitution - "Panel of the People", which stems from English common law and traces to the Magna Carta in 1215. It is the Fifth Amendment to the United States Constitution that mandates no person may be required to stand trial in Federal Court on a felony offense charge until an indictment is returned by a Grand Jury, unless that right is waived.
The Grand Jury is involved with matters of a criminal nature and does not decide civil disputes or determine guilt or innocence. A Grand Jury normally consists of 16 to 23 members. The United States Attorney, the prosecutor in Federal criminal cases, presents evidence to the Grand Jury for them to determine whether there is "probable cause" to believe that a crime has been committed by the individual to be charged. If the Grand Jury decides there is enough evidence, they will return an indictment against the defendant. Grand Jury proceedings are not open for public observation and all records are sealed.