As provided in 18 U.S.C. § 3331(a), the district court in every judicial district having more than four million inhabitants must impanel a special grand jury at least once every eighteen months (unless a special grand jury is then sitting); and the district court must also impanel a special grand jury when the Attorney General, Deputy Attorney General, or a designated Assistant Attorney General certifies in writing to the chief judge of the district that in his/her judgment, a special grand jury is necessary "because of criminal activity in the district." (See 28 C.F.R. § 0.59 under which the Assistant Attorney General in charge of the Criminal Division is designated to make certifications under 18 U.S.C. § 3331.)
District courts are authorized under 18 U.S.C. § 3332(b) to impanel additional special grand juries when the special grand juries already impaneled have more business than they can properly handle. When impaneling additional special grand juries, a court should make a finding as to the need; and a court should always make it clear that the special grand jury is being impaneled under 18 U.S.C. § 3331 (and is therefore not subject to the limitations of a regular grand jury). See Wax v. Motley, 510 F.2d 318 (2d Cir. 1975).
The special grand jury has a duty under 18 U.S.C. § 3332(a) "to inquire into offenses against the criminal laws of the United States alleged to have been committed within that district." Such alleged offenses may be brought to the jury's attention by the court or by any attorney appearing for the United States to present evidence to the jury. It is incumbent upon any such government attorney to whom it is reported that a Federal offense was committed within the district, if the source of information so requests, to refer the information to the special grand jury, naming the source and apprising the jury of the attorney's action or recommendation regarding the information.