New York Consolidated Laws, Family Court Act - FCT § 344.1. Rules of evidence;  proof of previous conviction or delinquency finding

1. If in the course of a juvenile delinquency proceeding, any witness, including a respondent, is properly asked whether he was previously convicted of a specified offense and answers in the negative or in an equivocal manner, the party adverse to the one who called him may independently prove such conviction.  If in response to proper inquiry whether he has ever been convicted of any offense the witness answers in the negative or in an equivocal manner, the adverse party may independently prove any previous conviction.

2. If a respondent in a juvenile delinquency proceeding, through the testimony of a witness other than respondent called by him, offers evidence of his good character, the presentment agency may independently prove any previous finding of delinquency of the respondent for a crime the commission of which would tend to negate any character trait or quality attributed to the respondent in such witness' testimony.