Judgment, Supreme Court, New York County (William Wetzel, J.), rendered May 4, 2000, convicting defendant, after a jury trial, of assault in the second degree and criminal possession of a weapon in the fourth degree, and sentencing him to concurrent terms of 2 years and 1 year, respectively, unanimously affirmed.
The verdict was based on legally sufficient evidence and was not against the weight of the evidence. The People established, through eyewitness testimony, that defendant cut the victim’s forehead with a box cutter. There is no basis upon which to disturb the jury’s determinations concerning credibility.
The court properly exercised its discretion in permitting the victim’s treating doctor, a first-year resident in emergency medicine with 10 months experience in that field, to also testify as an expert on that subject (see, People v Rogers, 163 AD2d 157, lv denied 76 NY2d 943; see also, Price v New York City Hous. Auth., 92 NY2d 553, 559).
The court properly permitted the People to introduce evidence which rebutted defendant’s claim that the victim’s injury resulted from blunt trauma rather than from a sharp instrument (see, People v Harris, 57 NY2d 335, 345, cert denied 460 US 1047). To the extent this evidence could have been introduced on the People’s direct case, the court properly exercised its discretion in permitting it to be introduced in rebuttal (see, CPL 260.30 [7]; People v Brown, 240 AD2d 281, lv denied 91 NY2d 870). Concur — Rosenberger, J. P., Mazzarelli, Ellerin, Wallach and Buckley, JJ.