(1) "Penal institution" means a jail, prison, penitentiary, house of correction, or other place of penal detention.
(2) "State" means any state or territory of the United States and the District of Columbia.
(3) "Summons" means a subpoena, order, or other notice requiring the appearance of a witness.
(4) "Witness" means a person whose testimony is desired in any proceeding or investigation by a grand jury or in a criminal prosecution or proceeding held by the prosecution or the defense, including a person who is confined in a penal institution in any state.