N.J. Stat. § 2A:67-28
In all cases in which the mental capacity of the party is to be determined, the testimony shall be taken orally and the judge may hear the matter without a jury or may direct that the action be tried by a jury called from the general panel or, if not available, by a jury specially summoned as in other actions.
In all other cases, the judge may hear the matter summarily on the complaint, return and answer to the return, or require that testimony be offered orally and, on its own motion, may summon witnesses and require any person to produce documents, records, or other writings.
In a proceeding under subsection d. of N.J.S. 2A:67-13, the judge may take testimony concerning the truth of affidavits and proofs upon which the order for process was made and process issued.
N.J.S. § 2A:67-28