how to impanel a federal grand jury
Thereafter, in the event the court excuses one of the initially selected jurors, it may then impanel the alternate. Courts in every federal judicial district empanel grand juries of 23 persons. Federal grand juries generally serve for 18 months. The 18 months begin to run from the date of empanelment. However, the district court may discharge the jury earlier, or extend the jury's service six additional months, if it finds the extension to be in the public interest.