—[*1] Elisa Barnes, New York, for appellant.

Michael A. Cardozo, Corporation Counsel, New York (Daniel A. Pollak of counsel), for presentment agency.

Order, Family Court, New York County (Mary E. Bednar, J.), entered on or about August 4, 2011, which adjudicated appellant a juvenile delinquent upon a fact-finding determination that he committed acts that, if committed by an adult, would constitute the crimes of robbery in the second degree, grand larceny in the fourth degree, criminal possession of stolen property in the fifth degree, jostling and menacing in the third degree, revoked appellant's probation and placed him with the Office of Children and Family Services for a period of 18 months, unanimously affirmed, without costs.

The court's finding was not against the weight of the evidence (see People v Danielson, 9 NY3d 342, 348-349 [2007]). There is no basis for disturbing the court's credibility determinations. Appellant's participation in the robbery was established by the testimony of police officers who observed the incident, and the victim's nonidentification of appellant was satisfactorily explained by the circumstances of the robbery.

The court properly exercised its discretion in qualifying a police witness as an expert on youth gangs and receiving his testimony at the dispositional hearing (see generally People v Lee, 96 NY2d 157, 162 [2001]). In [*2]any event, even without reference to the expert testimony, the disposition was appropriate, given that appellant committed a serious offense while already on probation. Concur—Tom, J.P., Mazzarelli, Moskowitz, Renwick and Abdus-Salaam, JJ.