In an action to recover damages for psychiatric malpractice, the plaintiff appeals from a judgment of the Supreme Court, Rockland County (Lefkowitz, J.), entered May 4, 1993, which, upon a jury verdict, is in favor of the defendants and against her dismissing the complaint.
*573Ordered that the judgment is affirmed, with costs.
The plaintiff commenced this action to recover damages from the defendants, alleging, inter alia, that the individual defendant psychiatrist (hereinafter the defendant) committed malpractice by engaging in a sexual relationship with her while she was his patient. The defendant essentially conceded that engaging in sexual relations with a patient would constitute malpractice, but denied that any sexual or otherwise improper relationship existed between the parties. After a lengthy trial, the jury rendered a verdict in favor of the defendant, specifically determining, inter alia, that an improper relationship between the parties had not existed. This appeal by the plaintiff ensued.
Contrary to the plaintiff’s contention, the Supreme Court properly rejected her requests during her case-in-chief to present the testimony of other women who would allege that the defendant also engaged in sexual relations with them while they were his patients. "A general rule of evidence, applicable in both civil and criminal cases, is that it is improper to prove that a person did an act on a particular occasion by showing that he did a similar act on a different, unrelated occasion. (See Richardson, Evidence [10th ed], §§ 170, 184.)” (Matter of Brandon, 55 NY2d 206, 210-211; see, Kourtalis v City of New York, 191 AD2d 480). While evidence of previous similar conduct may be admissible in a given case upon proof that one of the narrow exceptions to the general rule applies (see, Matter of Brandon, supra; People v Molineux, 168 NY 264), no such showing was made in the matter before us. The plaintiff’s suggestion that the proffered testimony should have been permitted pursuant to the common scheme or plan exception is without merit. Indeed, it is clear that these alleged similar instances, assuming they actually occurred, "were no more than 'separate and independent transaction^] entered into as the occasion arose and not in pursuance of any preconcerted general plan or design’ (People v Grutz, 212 NY 72, 79, supra)” (Matter of Brandon, supra, at 213). Moreover, the proffered testimony failed to satisfy any other exception to the rule precluding the admission of such evidence, and our dissenting colleagues concede that this ruling by the trial court was correct.
Similarly, the Supreme Court did not err in permitting the defendant to exhibit the surgical scars on his abdomen to the jury during the presentation of his direct case. The plaintiff had previously testified that even though she had engaged in a multiyear sexual relationship with the defendant, that she had *574seen him without his shirt on, and that she had performed countless acts of fellatio on him, she never observed the presence of any scar above his waist. While "it is axiomatic that a witness may not be contradicted by the introduction of extrinsic evidence regarding collateral matters for the sole purpose of impeaching his credibility” (People v Strawder, 106 AD2d 672, 673), "the question of whether a matter is collateral or not must be determined under the particular circumstances of each case” (People v Medina, 130 AD2d 515, 516). Contrary to the plaintiffs contention, the defendant’s physical appearance was not a mere collateral matter; rather, this evidence went to the central issue in this case — whether the parties engaged in a sexual relationship (see generally, People v Knight, 80 NY2d 845). Accordingly, the defendant was properly permitted to exhibit his torso to the jury and to thereby attempt to cast doubt on the plaintiff’s assertion that such a relationship existed.
The plaintiff and the dissent further maintain that the trial court erred in refusing to reopen the case to permit the plaintiff to call the alleged former patients as rebuttal witnesses. However, it is well settled that "[t]he question of whether to permit the introduction of rebuttal evidence rests within the sound discretion of the trial court and the court’s decision in that regard should not be disturbed on appeal absent a clear abuse or improvident exercise of discretion” (Capone v Gannon, 150 AD2d 749, 750; see, Saleh v Sears, Roebuck & Co., 119 AD2d 652). The plaintiff contends that these witnesses would have testified that they also had sexual relations with the defendant and did not observe his scars. However, as accurately noted by the trial court, the question of whether these other alleged former patients observed the defendant’s scars on other occasions is clearly collateral to the issue of whether the plaintiff observed them. Furthermore, the plaintiff had already attempted to explain her lack of observation in this regard by testifying that the defendant always kept his boxer shorts on during their alleged hurried sexual trysts in his office. Unlike the dissent, we do not find this particular aspect of the plaintiff’s testimony inherently incredible or contrary to human knowledge and experience, especially in view of the surreptitious nature of these purported sexual encounters and the unusual physical setting in which they allegedly occurred. More significantly, the proffered rebuttal testimony simply would not have rehabilitated the plaintiff’s credibility or rendered her account of her particular relationship with the defendant any more likely. Rather, the proposed evidence would only have unduly prejudiced the defendant by improp*575erly suggesting that he had a propensity for engaging in sexual relationships with patients (see generally, Matter of Brandon, 55 NY2d 206, supra), a suggestion which the trial court accurately found could not be avoided by the mere administration of a limiting instruction to the jury. Moreover, in evaluating the proffered testimony, the jurors would first have been required to determine whether these other alleged sexual relationships actually existed. Hence, introduction of the proffered testimony would have transformed the trial into a complex series of mini-trials regarding the validity of the rebuttal witnesses’ accounts, all for the legally impermissible purpose of demonstrating that the defendant purportedly had engaged in improper relationships with other patients on other occasions and therefore must have acted in the same fashion with respect to the plaintiff. Inasmuch as the prejudicial effect of the proposed rebuttal testimony and the unnecessary procedural complications it would have created far outweighed any negligible probative value which it might have had with respect to the genuine issues in this case, the trial court did not improvidently exercise its broad discretion in refusing to reopen the case to permit this collateral evidence (see, e.g., Capone v Gannon, supra; Saleh v Sears, Roebuck & Co., supra). In this regard, the plaintiff’s reliance on Roy v Hartogs (85 Misc 2d 891) is misplaced. The issue sought to be resolved in Roy dealt with the defendant’s claim of impotency, a matter central to the plaintiff’s claim of sexual intimacy because it raised the defense of physical impossibility. On the other hand, in this case the plaintiff sought to produce witnesses merely to buttress her contention that other claimed sexual partners also did not observe certain body scars on the defendant. As previously noted, this is purely a collateral issue.
The trial court did commit an error while marshalling the evidence by incorrectly stating that the defendant had denied ever having sex with other patients in his office. However, the error was clearly harmless. The court carefully instructed the jurors that their recollection of the evidence was controlling and, in any event, no issue regarding whether the defendant engaged in sexual relations with other patients was ever brought to the jury’s attention. Accordingly, the court’s misstatement on this irrelevant matter clearly had no bearing on the jury’s verdict.
The plaintiff’s remaining contentions are unpreserved for appellate review and, in any event, lack merit. Bracken, J. P., Sullivan and Pizzuto, JJ., concur.