Appeal from a judgment of the County Court of Tioga County (Siedlecki, J.), rendered June 17, 1988, upon a verdict convicting defendant of the crime of sexual abuse in the first degree.
Seeking reversal of his conviction, defendant contends that (1) County Court erred when it permitted a psychotherapist to testify on behalf of the prosecution with regard to the behavior of sexually abused children without ever interviewing the victim of the alleged abuse, (2) it was improper to permit the People to amend the indictment to conform to the proof as to the date of the alleged crime, and (3) the evidence was, as a matter of law, insufficient to establish defendant’s guilt beyond a reasonable doubt. In our view, the conviction should be affirmed.
The expert opinion evidence offered by the psychotherapist was to assist the jury in an area beyond the ordinary knowledge of the average juror, i.e., the psychological reactions of a child who is the victim of sexual abuse by a family member. Accordingly, there being a proper foundation for this testimony, the action of County Court was in the sound exercise of its discretion (see, People v Keindl, 68 NY2d 410, 422). We also find.no error in permitting the amendment of the indictment to conform to the proof of a two-day difference between the date alleged in the indictment and the date proven at trial (see, CPL 200.70 [1]). We note that defendant failed to seek an adjournment and was not prejudiced by the amendment (see, People v Johnson, 115 AD2d 794).
Finally, in our view the evidence in this record establishes defendant’s guilt beyond a reasonable doubt (see, CPL 60.20 [2] ; Penal Law § 130.16; People v Sinatra, 134 AD2d 738, lv denied 70 NY2d 1011).
*996Judgment affirmed. Mahoney, P. J., Kane, Levine, Mercure and Harvey, JJ., concur.