N.J. Stat. Ann. § 2C:4-10

A statement made by a person subjected to psychiatric or psychological examination or treatment pursuant to section 2C:4-5, 2C:4-6 or 2C:4-9 for the purposes of such examination or treatment shall not be admissible in evidence against him in any criminal proceeding on any issue other than that of his mental condition but it shall be admissible upon that issue, whether or not it would otherwise be deemed a privileged communication. When such a statement constitutes an admission of guilt of the crime charged or of an element thereof, it shall only be admissible where it appears at trial that conversations with the examining psychiatrist or licensed psychologist were necessary to enable him to form an opinion as to a matter in issue.