New Jersey Statutes Title 2A. Administration of Civil and Criminal Justice 2A § 81-17.2a2

If any public employee, having claimed the privilege against self-incrimination, testifies before any court, grand jury or the State Commission of Investigation after having been informed that his failure to appear and testify would subject him to removal from his office, position or employment, such testimony and the evidence derived therefrom shall not be used against such public employee in a subsequent criminal proceeding under the laws of this State; provided that no such public employee shall be exempt from prosecution or punishment for perjury or false swearing committed while so testifying.