N.J. Stat. Ann. § 33:1-58

The officer or officers to whom the search warrant is directed may break open any outer or inner door or window of any premises, building, vehicle or other place, or anything contained therein, to execute the warrant if, after pronouncement of his authority and purpose, he does not receive admission, and also when necessary for his own liberation or that of any person aiding him in the execution of the warrant.