N.J. Stat. § 53:1-21
The superintendent may, with the approval of the governor, and if in his opinion the detective work of the state police so demands, create a state detective bureau, under his immediate supervision. The bureau shall maintain facilities for the detection of crime by the state police, and shall co-operate with and afford central information and fingerprints and other records for the various counties. For this purpose, the superintendent may, with the approval of the governor, utilize the services of not more than five of the members of the state police force as assistant state detectives.
All applicants for detective work shall first be given a special examination by the superintendent to determine their qualifications and experience for such work.
N.J.S. § 53:1-21