A criminal case in federal court is initiated with an indictment.  An indictment is a formal accusation by the federal government that an individual committed a crime.  Indictments are obtained when a prosecutor from the U.S. Attorney’s office presents evidence to a federal grand jury that indicates a person committed a crime. The U.S. attorney attempts to convince the grand jury that the evidence is strong enough to show that the person committed the crime and should be formally charged. If the grand jury agrees with the prosecutor, it will issue an indictment.  Once the indictment is issued, the accused must go before the court after either being summoned to court or arrested. 

A grand jury is charged only with determining whether the person may be tried for a crime, not whether they are actually guilty.  Grand jury indictments primarily involve felonies such as cross state drug sales and other violations of federal laws.