Whenever the terms of an agreement with a criminal witness provide for him or her to serve a period of incarceration in the state, his or her confinement shall be either at the adult correctional institutions (ACI) or at a facility maintained and supervised by the state police. The court by order shall set forth whether custody of the criminal witness shall be maintained by the department of corrections or the state police. If the place of confinement is other than at the ACI, the witness shall be under guard by law enforcement officials at all times. He or she shall not be permitted to leave the place of confinement unless escorted by a law enforcement guard. The officers selected to guard the witness shall have no other involvement in the case or cases in which the witness is providing evidence.