N.J. Stat. § 30:4A-6
If the person, for whom the diagnosis is sought, is confined by virtue of any type of criminal or other process, then admission to the diagnostic center may be secured upon application to the Commissioner of the Department of Institutions and Agencies, who may, after examination of the facts and circumstances, arrange for the transfer of such person from his place of confinement to the diagnostic center. Such person shall remain in the diagnostic center for a period not exceeding ninety days, during which time a complete diagnosis shall be made and a report and recommendation thereon in writing given to the agency requesting the service. Upon completion of the diagnosis, the commissioner shall order the retransfer of the person to his former place of confinement, there to be dealt with in accordance with the statutes in such case made and provided. If necessary, the center may make said retransfer to the former place of confinement.
N.J.S. § 30:4A-6