(1) The district courts are hereby vested with power to call grand juries.
(2) A grand jury may be called and summoned in the manner provided by law on such day of a regular term of the district court in each year in each county of the state as the district court may direct and at such other times and upon such notice as the district court may deem necessary.
(3) District courts shall call a grand jury in each case that a petition meets the requirements of section 32-628, includes a recital as to the reason for requesting the convening of the grand jury and a specific reference to the statute or statutes which are alleged to have been violated, and is signed not more than ninety days prior to the date of filing under section 29-1401.02 by not less than ten percent of the registered voters of the county who cast votes for the office of Governor in such county at the most recent general election held for such office.
(4) District courts shall call a grand jury in each case upon certification by the county coroner or coroner's physician that a person has died while being apprehended by or while in the custody of a law enforcement officer or detention personnel. In each case subject to this subsection:
(a) Law enforcement personnel from the jurisdiction in which the death occurred shall immediately secure the scene, preserve all evidence, and investigate the matter as in any other homicide. The case shall be treated as an open, ongoing matter until all evidence, reports, and other relevant material which has been assembled are transferred to a prosecuting attorney selected pursuant to subdivision (b) of this subsection;
(b) The county attorney or a member of his or her staff shall be the prosecuting attorney. Except as provided in subdivision (d) of this subsection, the prosecuting attorney shall, as soon as practicable, select a team of three peace officers trained to investigate homicides. At least two of such investigators shall be from agencies other than the agency under which the death occurred. The team shall examine all evidence concerning the cause of death and present the findings of its investigation to the prosecuting attorney;
(c) A grand jury shall be impaneled within thirty days after the certification by the county coroner or coroner's physician, unless the court extends such time period upon the showing of a compelling reason; and
(d) In those cases in which the death has been certified by a licensed practicing physician to be from natural causes, the county attorney or a member of his or her staff may present such finding to a grand jury without selecting a three-member team of peace officers to investigate.