Because of the Fifth Amendment, the federal legal system has to use grand juries to bring charges, at least for certain offenses.
The Fifth Amendment to the U.S. Constitution requires that charges for all capital and "infamous" crimes be brought by an indictment returned by a grand jury.
The amendment has been interpreted to require that an indictment be used to charge federal felonies, unless a defendant waives his or her right to be indicted by a grand jury.
The Supreme Court has held that this part of the Fifth Amendment is not binding on the states, so they can use grand juries or not, as they wish.
If a defendant waives his or her right to be indicted by a grand jury, the prosecutor can charge them by using an "information." An information is simply a pleading that accuses the defendants of committing crimes, just as an indictment does.
The difference between an indictment and an information is that a grand jury must approve an indictment, while a prosecutor can issue an information without the grand jury's approval or, for that matter, without ever showing the information to the grand jury.
Since most federal prosecutions involve felony charges, grand juries play an important role in enforcing federal criminal law.
