Judgment unanimously reversed on the law and indictment dismissed. Memorandum: Upon the exercise of our factual review powers (CPL 470.15 [1]; 470.20 [5]), we conclude that the People failed to meet their burden of disproving defendant’s alibi defense beyond a reasonable doubt (see, People v Victor, 62 NY2d 374, 377-378). Defendant’s *954proof established that between 8:00 and 8:30 a.m. on October 6, 1987, the time of the alleged assault, defendant was confined to a locked psychiatric ward at the Buffalo Psychiatric Center. Employees of the Center testified, and the Center’s records showed, that defendant was present at the 7:30 and 9:00 a.m. roll calls in his ward and was administered medication between 7:45 and 8:15 a.m. on October 6, 1987. Additionally, the Center’s records indicate that defendant was never reported missing from this locked ward. The mere possibility that defendant could have escaped from the ward, committed the assault and returned is, in our opinion, insufficient to disprove defendant’s alibi beyond a reasonable doubt. We further note that the credibility of claimant’s identification of defendant was substantially weakened by the fact that she failed to indicate to the authorities that her assailant was the same person with whom she had a heated and lengthy confrontation a month earlier. (Appeal from judgment of Supreme Court, Erie County, Kubiniec, J. — assault, second degree.) Present — Callahan, J. P., Denman, Green, Pine and Lawton, JJ.