Cordy, J.
Following a jury trial, Rhonda Adjutant, a woman employed by an escort service, was found guilty of voluntary manslaughter for killing Stephen Whiting, a client of the service. In this appeal, Adjutant argues that evidence of Whiting’s violent reputation and past conduct, even though unknown to her at the time of the killing, should have been admitted at her trial because it was relevant to her claim that Whiting was the [650]*650“first aggressor” in the altercation that resulted in his death, and that she acted in self-defense.
After surveying the state of the law in jurisdictions throughout the country, we are persuaded that evidence of a victim’s prior violent conduct may be probative of whether the victim was the first aggressor where a claim of self-defense has been asserted and the identity of the first aggressor is in dispute.1 Consequently, when such circumstances are present, we hold, as a matter of common-law principle, that trial judges have the discretion to admit in evidence specific incidents of violence that the victim is reasonably alleged to have initiated. While there is potential for confusion and prejudice inherent in the admission of this type of evidence, trial judges are well equipped to decide whether the probative value of the evidence proffered outweighs its prejudicial effect in the context of the facts and issues presented in specific cases.
In the present case, relying on language in past decisions of this court, see, e.g., Commonwealth v. Graham, 431 Mass. 282, 291 (2000); Commonwealth v. Dilone, 385 Mass. 281, 285-286 (1982), the judge ruled that she lacked the discretion to admit evidence of prior violent acts committed by Whiting but unknown to Adjutant. Because we conclude that the judge’s ruling, while understandable, was prejudicial to Adjutant’s claim that she acted in self-defense, we reverse the judgment and remand the case for a new trial.
1. Background. The evidence at trial was as follows. Adjutant worked as an escort for Newbury Cosmopolitan International Escort Service (Newbury). In the early morning of September 25, 1999, Whiting telephoned Newbury and requested an escort. The Newbury dispatcher told Whiting that he could receive a full body massage and one hour of an escort’s company for $175. Whiting agreed to these terms, and arrangements were made for Adjutant to visit Whiting’s home in Revere. Shortly thereafter, Adjutant was dropped off there by a driver and the dispatcher’s boy friend (drivers). Whiting met her outside his building and accompanied her to his basement apartment.
Once inside, Whiting paid Adjutant, who then telephoned [651]*651Newbury to report that she had received payment. Adjutant testified that during and after the call Whiting snorted two lines of cocaine. Adjutant then offered to begin a massage. Whiting replied that he wanted intercourse and believed that he had paid for it. Adjutant denied that she was sent to have intercourse with him, and telephoned the Newbury dispatcher on her cellular telephone to inform her that Whiting wanted more than a massage. Adjutant then handed the phone to Whiting, and the dispatcher reminded him of the original terms. Whiting demanded a total refund, which neither the dispatcher nor Adjutant offered. When Whiting returned the telephone to Adjutant, the dispatcher told her to leave and agreed to stay on the line until Adjutant was out of the apartment.
There was conflicting testimony as to when the defendant and the victim armed themselves for their fatal confrontation. Adjutant testified that when she attempted to leave, Whiting pushed her onto his bed and retrieved a crowbar from the kitchen, at which point Adjutant picked up a knife that was lying on the bedside table, next to a plate of cocaine. The dispatcher, on the other hand, testified that while she was talking to Whiting, he said that Adjutant had a knife, and that when Adjutant then got back on the telephone with her, Adjutant said that Whiting was picking up a crowbar.
In any event, after arming himself, Whiting first slammed the crowbar on a counter and then swung it at Adjutant, striking her in the leg. She responded by nicking him in the face with the knife, drawing blood. Adjutant testified that she next tried to avert further confrontation by offering to begin again with a massage, but Whiting refused. Meanwhile, at Adjutant’s urging, the dispatcher alerted Adjutant’s drivers to return to Whiting’s apartment. At this point, Adjutant testified that she attempted to run toward the door, but Whiting tackled her. During the struggle, Adjutant stabbed Whiting in the shoulder with the knife and moved away. Whiting, however, continued to block Adjutant’s exit, while Adjutant screamed at him to stay back and threatened to cut him again if he came any closer.2
Within minutes, Adjutant’s drivers returned to the scene, [652]*652heard her screams, and kicked in the door to the apartment. According to Adjutant, the moment one of the drivers kicked in the door, Whiting advanced on her with the crowbar raised, at which point she stabbed him in the neck, inflicting the fatal wound. Whiting did not immediately drop the crowbar or move away from the door. When he eventually did, Adjutant fled the apartment with the drivers, throwing down the knife and her telephone.3 One of the drivers provided a different account of the fatal stabbing. He testified that after the door was kicked open, Whiting turned to face the drivers, at which point he saw Adjutant move toward Whiting and stab him in the neck in a straightforward thrusting motion. The medical examiner’s testimony concerning the likely manner in which the fatal knife wound was inflicted was not entirely consistent with the driver’s testimony.
Adjutant maintained at trial that all her actions were defensive and intended to help her escape the apartment. The jury’s main task was determining whether Adjutant acted in self-defense. That inquiry required the jury to weigh Adjutant’s credibility, as well as that of the dispatcher and the driver, and decide who moved first to attack the other during the last moments of the standoff. See Commonwealth v. Kendrick, 351 Mass. 203, 210-212 (1966).
In her defense, Adjutant focused on Whiting’s intoxication and drug use that evening. The medical examiner testified at trial that Whiting had cocaine in his bloodstream, and that his blood alcohol level reflected his consumption of the equivalent of sixty ounces of beer or five ounces of whiskey. Two of Whiting’s neighbors testified that, earlier that evening, Whiting appeared intoxicated and had made unsuccessful sexual advances toward women near the apartment building. Adjutant testified that she became terrified when her initial blows to Whiting did not seem to faze him, apparently because of his drugged condition.
During the trial, Adjutant’s counsel sought to cross-examine [653]*653Whiting’s neighbors about his previous violent behavior and reputation for violence. The judge sustained the prosecutor’s objections to these questions and also barred testimony about Whiting’s behavior while intoxicated, ruling that Whiting’s violent past or reputation for violence was only relevant if Adjutant had been aware of them at the time of the stabbing.4 When the prosecution subsequently elicited testimony that Whiting was “calm,” “talked . . . very softly,” and “sounded like a nice person” on the night of the incident, defense counsel moved for permission to “impeach” this testimony by evidence of Whiting’s prior acts of aggression. The judge denied the motion, except insofar as to permit Adjutant to introduce percipient witness testimony to Whiting’s previous use of a crowbar. No such witnesses were called.5
At the conclusion of the trial, the jury convicted Adjutant of voluntary manslaughter.6 She appealed and the Appeals Court affirmed the conviction. Commonwealth v. Adjutant, 60 Mass. App. Ct. 1107 (2003). We granted her application for further appellate review limited to whether the trial judge erred in [654]*654concluding that she had no discretion to admit Adjutant’s proffered evidence and consequently excluding it.
2. Discussion. In almost every American jurisdiction, evidence of a victim’s violent character may be admitted to support an accused’s claim of self-defense under two distinct theories. First, it may be admitted to prove that at the time of the assault the defendant was reasonably apprehensive for his safety, and used a degree of force that was reasonable in light of the victim’s violent tendencies. Because such evidence is relevant to the defendant’s state of mind (the subjective reasonableness of his apprehension and actions), a predicate to its admissibility is the defendant’s prior knowledge of it. Second, it may be admitted as tending to prove that the victim and not the defendant was likely to have been the “first aggressor,” where there is a dispute as to who initiated the attack. Under the first theory, the evidence is not admitted for the purpose of showing that the victim acted in conformance with his character for violence; under the second theory, it is.
Massachusetts has long followed the evidentiary rule that permits the introduction of evidence of the victim’s violent character, if known to the defendant, as it bears on the defendant’s state of mind and the reasonableness of his actions in claiming to have acted in self-defense. See Commonwealth v. Edmonds, 365 Mass. 496, 502 (1974) (victim’s reputation as violent person admissible). See also Commonwealth v. Fontes, 396 Mass. 733, 735-736 (1986) (instances of victim’s prior acts of violence admissible). This court has not, however, had occasion to rule on the second theory, raised in this case, regarding the use of such evidence to prove who was the first aggressor. Id. at 736 n.1 (“It should be recognized that we are not considering here the admission of evidence of general reputation or of specific incidents of violence to show that the victim was, or was likely to have been, the aggressor”).
Under Rules 404 and 405 of the Federal Rules of Evidence, all Federal courts now permit the introduction of evidence of the victim’s violent character to support a defendant’s self-[655]*655defense claim that the victim was the first aggressor.7 Similarly, appellate courts in forty-five of the forty-eight State jurisdictions that have considered the issue have decided that some form of such evidence is properly admissible on the first aggressor issue, regardless whether the victim’s violent character was known to the defendant at the time of the assault.8 The two [656]*656States that have not considered the matter have both adopted versions of Federal Rules of Evidence9 that would appear to permit the introduction of such evidence. Of the three State appellate courts that have declined to follow the modern trend, two did so over vigorous dissents.10
The basis of the overwhelming trend toward admitting some form of this evidence can be found in the view that evidence reflecting the victim’s propensity for violence has substantial probative value and will help the jury identify the first aggressor when the circumstances of the altercation are in dispute. People v. Lynch, 104 Ill. 2d 194, 200 (1984). See, e.g., United States v. Burks, 470 F.2d 432, 434-435 (D.C. Cir. 1972) (evidence of deceased’s violent character relevant and admissible where evidence “inconsistent” on identity of aggressor [657]*657“[i]n order to corroborate” defendant’s account); State v. Griffin, 99 Ariz. 43, 46-47 (1965), quoting Mendez v. State, 27 Ariz. 82, 84 (1924), (“It is the rule that where it is questionable as to which was the aggressor . . . the general reputation of the deceased as a dangerous, turbulent, and violent man may always be shown”). “Evidence probative of the victim’s reputation for violence is highly relevant and admissible to show . . . that the victim was the aggressor in a case in which self-defense is raised.” State v. Soto, 477 A.2d 945, 949 (R.I. 1984). See United States v. Greschner, 647 F.2d 740, 741 (7th Cir. 1981) (“ ‘violent character’ line of proof is relevant to the defendant’s theory of self-defense in that it makes his version that the victim attacked him ‘more probable’ ”). See also State v. Dellay, 687 A.2d 435, 438 n.1 (R.I. 1996) (noting scientific evidence for and against “premise for character evidence is that personality may be defined in terms of traits that produce consistent forms of behavior”); Lolley v. State, 259 Ga. 605, 609-610 (1989) (Weltner, J., concurring), quoting Henderson v. State, 234 Ga. 827, 830 (1975) (“It is more probable that a person will act in accordance with his character [disposition] than that he will act contrary to it”); United States v. Keiser, 57 F.3d 847, 853 (9th Cir.), cert. denied, 516 U.S. 1029 (1995) (whether victim was man with history and reputation for violence makes it “more likely that his behavior on the night of the [incident] was violent — which supports the defendant’s defense. . . — than it would be if [the victim] were peaceable”). In the words of Professor Wigmore, “When the issue of self-defense is made in a trial for homicide, and thus a controversy arises whether the deceased was the aggressor, one’s persuasion will be more or less affected by the character of the deceased; it may throw much light on the probabilities of the deceased’s action.” 1 J. Wigmore, Evidence § 63, at 467 (3d ed. 1940).
There can be no doubt that at least some of the proffered evidence in this case was relevant to Adjutant’s self-defense claim.11 Whether Whiting was a violent man, prone to aggression when intoxicated or under the influence of drugs, “throws [658]*658light” on the crucial question at the heart of Adjutant’s self-defense claim — who attacked first in the final moments before the fatal stabbing. Commonwealth v. Woods, 414 Mass. 343, 356, cert. denied, 510 U.S. 815 (1993), quoting Commonwealth v. Palladino, 346 Mass. 720, 726 (1964). The evidence, if admitted, would have supported the inference that Whiting, with a history of violent and aggressive behavior while intoxicated, probably acted in conformity with that history by attacking Adjutant, and that the defendant’s story of self-defense was truthful. State v. Miranda, 176 Conn. 107, 113-114 (1978).12
The Commonwealth argues that juries invariably will be distracted by information about the victim’s unrelated prior violence. We disagree. This court has previously approved the admission of evidence of a victim’s history of violence, when known to the defendant. Commonwealth v. Fontes, 396 Mass. 733, 736 n.1 (1986). If juries are capable of receiving such evidence for the limited purpose of evaluating the reasonableness of a defendant’s apprehension, they are capable of weighing similar evidence relevant to the first aggressor issue. While we acknowledge that there is a possibility that juries may misunderstand the purpose for which the evidence is offered, and agree that they should be specifically instructed on that point, the greater danger here is prejudice to the defendant’s case. We share the preference of the Supreme Court of Illinois that the jury should have as complete a picture of the (often [659]*659fatal) altercation as possible before deciding on the defendant’s guilt:
“[T]he evidence of what happened here, as is often the case where self-defense is raised, is both incomplete and conflicting. Everything happened in an instant .... The witnesses could hardly analyze the scene in any great detail, or remember and describe it with precision. They could only form quick impressions. To decide what really occurred the jury needed all the available facts, including evidence of [the victim’s prior violence]. We hold that when the theory of self-defense is raised, the victim’s aggressive and violent character is relevant to show who was the aggressor, and the defendant may show it by appropriate evidence, regardless of when he learned of it.”
People v. Lynch, 104 Ill. 2d 194, 200 (1984).
Moreover, admission of evidence showing the victim’s prior violent acts on the first aggressor issue reflects the principle that “in criminal cases there is to be greater latitude in admitting exculpatory evidence than in determining whether prejudicial potentialities in proof offered to show guilt should result in its exclusion.” Matter of Robert S., 52 N.Y.2d 1046, 1053 (1981) (Fuchsberg, J., dissenting), citing 1 J. Wigmore, Evidence § 194 (3d ed. 1940) (criticizing New York rule excluding victim’s specific acts of violence to show propensity).13 “Where the victim’s propensity for violence is in question . . . the danger of prejudice to the defendant lies in refusing to admit such evidence.” People v. Lynch, supra at 201. See State v. Wilson, 236 Iowa 429, 443 (1945) (“The admission of this testimony was especially important to the [defendant], and for that reason its rejection was especially prejudicial to him. For if the homicide was justifiable because [the defendant] struck in self-defense, no crime was committed”). In this case, the judge’s exclusion of evidence of Whiting’s prior acts of violence kept from the jury relevant and [660]*660potentially exculpatory information about the probability that Whiting attacked Adjutant first in their final altercation.
Notwithstanding our usual hesitation to allow the admission of character evidence to prove conduct, see P.J. Liacos, M.S. Brodin, & M. Avery, Evidence § 4.4.1, at 130 (7th ed. 1999),14 we are persuaded that some form of evidence tending to show the victim’s violent character should be admissible for the limited purpose of supporting the defendant’s self-defense claim that the victim was the first aggressor. We now turn to the separate question of the permissible form of such evidence.
The defendant urges the court to allow the admission of [661]*661evidence both of the victim’s violent reputation and of his specific violent acts. The Commonwealth argues that if the court permits character evidence to be admitted, it should be limited to specific acts of violence committed by the victim. All other State jurisdictions that admit character evidence in these circumstances admit reputation evidence. Some of these States also admit evidence of specific violent acts.15
The arguments against admitting specific violent acts include (1) the danger of ascribing character traits to a victim with proof of isolated incidents, (2) the worry that jurors will be invited to acquit the defendant on the improper ground that the victim deserved to die, (3) the potential for wasting time trying collateral questions surrounding the victim’s past conduct, (4) the unfair difficulty of rebuttal by the prosecution, and (5) the strategic imbalance that flows from the inability of prosecutors to introduce similar evidence of the defendant’s prior bad acts. See Chandler v. State, 261 Ga. 402, 409 (1991) (Benham, J., concurring specially); Henderson v. State, 234 Ga. 827, 829 (1975); State v. Jacoby, 260 N.W.2d 828, 838 (Iowa 1977); Williams v. State, 565 S.W.2d 503, 505 (Tenn. 1978). See also Note, A New Understanding of Specific Act Evidence in Homicide Cases Where the Accused Claims Self-Defense: Striking the Proper Balance Between Competing Policy Goals, 32 Ind. L. Rev. 1437, 1447-1448 (1999). Many courts that follow the Federal Rules of Evidence rely on the Federal Rules [662]*662advisory committee’s note’s succinct rationale for exclusion: “Of the three methods of proving character [reputation, opinion, and specific instances of conduct,] evidence of specific instances of conduct is the most convincing. At the same time it possesses the greatest capacity to arouse prejudice, to confuse, to surprise, and to consume time.” Advisory Committee’s Note, Fed. R. Evid. 405, 56 F.R.D. 183, 222 (1972). See United States v. Smith, 230 F.3d 300, 308 (7th Cir. 2000), cert. denied, 531 U.S. 1176 (2001); United States v. Keiser, 57 F.3d 847, 855 n.16 (9th Cir. 1995); Daniel v. State, 78 P.3d 890, 901 (Nev. 2003).
While we acknowledge the validity of these concerns, we disagree that they require an unbending rule excluding all of the victim’s specific acts of violence when relevant to the identity of the first aggressor.16 This court rejected similar arguments in Commonwealth v. Fontes, 396 Mass. 733, 736-737 (1986), and approved the admission of such evidence when relevant to the defendant’s reasonable apprehension of imminent bodily harm.17 Testimony about the victim’s prior acts of violence can be convincing and reliable evidence of the victim’s propensity for violence. See, e.g., State v. Miranda, 176 Conn. 107, 113-114 (1978); Lolley v. State, 259 Ga. 605, 608-610 (1989) (Weltner, J., concurring); People v. Lynch, 104 Ill. 2d 194, 201-202 [663]*663(1984); Commonwealth v. Beck, 485 Pa. 475, 478-479 (1979). Such evidence becomes relevant to the first aggressor issue when the prior acts of violence demonstrate a propensity for initiating violence. “Such instances may be very significant; their number can be controlled by the trial court’s discretion; and the prohibitory considerations applicable to an accused’s character . . . have here little or no force.” 1A J. Wigmore, Evidence § 63.1, at 1382 (Tillers rev. ed. 1983). See Annot., 1 A.L.R.3d 571, 601 (1965).
In general, “[Relevant evidence is admissible unless unduly prejudicial, and, ‘[i]n weighing the probative value of evidence against any prejudicial effect it might have on a jury, we afford trial judges great latitude and discretion ....’” Commonwealth v. Arroyo, 442 Mass. 135, 144 (2004), quoting Commonwealth v. Sicari, 434 Mass. 732, 752 (2001), cert. denied, 534 U.S. 1142 (2002). When the prosecution seeks to introduce evidence of the defendant’s prior bad acts to show a common scheme, pattern of operation, absence of accident or mistake, identity, intent, or motive, the trial judge must weigh the acts’ probative value and the potential for prejudice to the defendant. Commonwealth v. Marshall, 434 Mass. 358, 366 (2001). Commonwealth v. Snell, 428 Mass. 766, 777, cert. denied, 527 U.S. 1010 (1999). Similarly, when the prosecution seeks to impeach a defendant’s testimony with his prior convictions, the trial judge has discretion to admit those convictions, so long as they are noncumulative and probative of the defendant’s truthfulness. Commonwealth v. Leftwich, 430 Mass. 865, 869 (2000).
We are persuaded that the sound discretion of trial judges to exclude marginally relevant or grossly prejudicial evidence can prevent the undue exploration of collateral issues. See, e.g., State v. Miranda, supra at 114; State v. Baca, 114 N.M. 668, 673 (1992). It is for the trial judge to evaluate the proffered evidence’s probative value and admit so much of that evidence as is noncumulative and relevant to the defendant’s self-defense claim.18 See People v. Wright, 39 Cal. 3d 576, 587 (1985) (upholding judge’s discretionary exclusion of specific acts when [664]*664“of little if any probative value”); State v. Miranda, supra; State v. Basque, 66 Haw. 510, 515 (1983); State v. Baca, supra (notwithstanding rule allowing admission of victim’s specific acts of violence, “trial court could very well have excluded the evidence based on its relative lack of probative value”). In addition, through their instructions, trial judges should mitigate the dangers of prejudice and confusion inherent in introducing evidence of the victim’s specific acts of violence by delineating the precise purpose for which the evidence is offered.
For these reasons, where the identity of the first aggressor is in dispute and the victim has a history of violence, we hold that the trial judge has the discretion to admit evidence of specific acts of prior violent conduct that the victim is reasonably alleged to have initiated, to support the defendant’s claim of self-defense.
With respect to the usefulness of reputation evidence in the context of establishing who was the first aggressor, we are presently of a different view. While such evidence may be quite probative in evaluating a defendant’s subjective state of mind, and the reasonableness of the actions thereby taken to defend himself, it is far less reliable in the present context. Reputation evidence is often “opinion in disguise.” Advisory Committee’s Note, Fed. R. Evid. 405, 56 F.R.D. 183, 222 (1972). We do not allow the admission of the private opinions of individual witnesses as character evidence. See Commonwealth v. Connolly, 356 Mass. 617, 626, cert. denied, 400 U.S. 843 (1970). See also Commonwealth v. Belton, 352 Mass. 263, 269, cert. denied, 389 U.S. 872 (1967) (defendant prohibited from introducing character evidence of his peacefulness in form of private opinions). Reputations or opinions are often formed based on rumor or other unreliable hearsay sources, without any personal knowledge on the part of the person holding that opinion. See Advisory Committee’s Note, Fed. R. Evid. 405, supra, quoting [665]*6657 J. Wigmore, Evidence § 1986 (describing reputation evidence as “secondhand, irresponsible product of multiplied guesses and gossip”). In this case, had Adjutant offered the testimony of Whiting’s neighbors that Whiting was known to be a violent man, without the corroborating details of the victim’s specific acts, such evidence would have been little more than a few neighbors’ accumulated opinions. Juries should have the ability to draw their own inferences in assessing the bearing of the victim’s prior violent conduct on the probability that he was the first aggressor.
Jurisdictions that exclude the victim’s specific acts of violence and admit reputation evidence make that choice because reputation evidence is filtered, general in nature, with less potential to inflame or sidetrack the proceedings than evidence of the victim’s specific acts — in essence, because such evidence is less “convincing” and thus less controversial. See Advisory Committee’s Note, Fed. R. Evid. 405, supra (“When character is used circumstantially and hence occupies a lesser status in the case, proof may be only by reputation and opinion”); McCormick, Evidence § 186, at 650 (5th ed. 1999) (“As one moves from the specific to the general in this fashion, the pungency and persuasiveness of the evidence declines ... .”). Given our rationale for allowing the admission of prior acts of violent conduct initiated by the victim, we favor the admission of concrete and relevant evidence of specific acts over more general evidence of the victim’s reputation for violence. Evidence of specific acts also lends itself more readily to the necessary weighing of probative value against prejudicial effect in the factual context of particular cases.
While constrained by the trial judge’s sound discretion, the defendant’s ability to introduce evidence of the victim’s prior history as a violent aggressor should also be matched with safeguards for prosecutors. See, e.g., 1A J. Wigmore, Evidence § 63, at 1369-1373 (Tillers rev. ed. 1983); Chandler v. State, 261 Ga. 402, 407-408 (1991). A defendant who intends to introduce evidence of the victim’s specific acts of violence to support a claim that the victim was the first aggressor must provide notice to the court and the Commonwealth of such intent and of the specific evidence he intends to offer. This [666]*666notice must come sufficiently prior to trial to permit the Commonwealth to investigate and prepare a rebuttal. The prosecutor, in turn, must provide notice to the court and the defendant of whatever rebuttal evidence he or she intends to offer at trial.19
Applying these rules to the proceedings in this case could have led to the introduction of some of the proffered evidence of Whiting’s prior acts of violence. “Nonconstitutional errors, preserved or resurrected below, are reviewed according to a nonprejudicial error standard.” Commonwealth v. Vinnie, 428 Mass. 161, 163, cert. denied, 525 U.S. 1007 (1998). We cannot say that the judge’s exclusion of the evidence was nonprejudicial. See Commonwealth v. Flebotte, 417 Mass. 348, 353 (1994). “The essential question is whether the [erroneously admitted evidence] had, or might have had, an effect on the jury and whether [it] contributed to or might have contributed to the verdicts.” Commonwealth v. Perrot, 407 Mass. 539, 549 (1990). Here, the proffered evidence went directly to the heart of the case’s central dispute — whether Whiting was the initial aggressor in his final altercation with Adjutant. Given the probative value of the excluded evidence, it may have been enough to create reasonable doubt of the defendant’s guilt. Although the judge might properly have excluded the evidence within her discretion after weighing its probative value against its prejudicial effect, we do not speculate as to what the judge would have done had she recognized her discretion. “Where the record shows that the judge has failed to exercise discretion, there exists an error of law requiring reversal.” Commonwealth v. Boyer, 400 Mass. 52, 57 (1987).
[667]*6673. Conclusion. This opinion adopts a new common-law rule of evidence. Because the defendant alleged the error and argued for the rule on direct appeal, she should have the benefit of this decision. Otherwise, it shall apply only prospectively. Commonwealth v. Dagley, 442 Mass. 713, 721 n.10 (2004).
The judgment against the defendant is reversed, the verdict is set aside, and the case is remanded to the Superior Court for a new trial and further proceedings consistent with this opinion.
So ordered.