As used in this act:

1. “Penal institution” means a jail, prison, penitentiary, house of correction, or other place of penal detention or place where the prisoner is required to reside or report in lieu of penal detention, including, but not limited to house arrest, half-way houses, community or treatment centers;

2. “State” means a state of the United States, the District of Columbia, the Commonwealth of Puerto Rico, or any territory of the United States;

3. “Witness” means a person who is confined in a penal institution in a state and whose testimony is desired in another state by a grand jury or other criminal proceeding before a court.