Victims or witnesses who have been subpoenaed to testify shall not be discharged or penalized or so threatened by his employer by reason of his attendance as a witness at a criminal proceeding. A victim or witness who notifies his employer of his subpoena to appear as a witness prior to his attendance, shall not be discharged or suffer other penalties by his employer. Any employer who discharges or disciplines or so threatens a subpoenaed victim or witness who must attend court to give testimony may be subject to the sanctions stated in section fourteen A of chapter two hundred and sixty-eight.