New Jersey Statutes Title 2C. The New Jersey Code of Criminal Justice 2C § 104-5

a. A law enforcement officer may arrest an alleged material witness without a warrant only if the arrest occurs prior to the filing of an indictment, accusation or complaint for a crime or the initiation of a criminal investigation before a grand jury, and if the officer has probable cause to believe that:

b. Following the warrantless arrest of an alleged material witness, the law enforcement officer shall bring the person immediately before a judge. If court is not in session, the officer shall immediately bring the person before the emergency-duty Superior Court judge. The judge shall determine whether there is probable cause to believe that the person is a material witness of a crime and, if an indictment, accusation or complaint for that crime has not issued or if a grand jury has not commenced a criminal investigation of that crime, the judge shall determine whether there is probable cause to believe that, within 48 hours of the arrest, an indictment, accusation or complaint will issue or a grand jury investigation will commence. The judge then shall proceed as if an application for a warrant has been made under N.J.S. 2C:104-4.