As used in this chapter:
"State" includes any state, territory, or possession, of the United States, the Commonwealth of Puerto Rico, and the District of Columbia.
"Summons" includes a subpoena ad testificandum and subpoena duces tecum, order, or other notice requiring the appearance of a witness.
"Witness" includes a person whose testimony is desired in any proceeding or investigation by a grand jury or in a criminal action, prosecution, or proceeding.