(concurring, with whom Abrams and Greaney, JJ., join). The defendant was convicted by a Superior Court jury of aggravated rape, kidnapping, and assault and battery. He was sentenced to serve from seven to ten years on the aggravated rape charge, and from three to five years on the kidnapping charge, to run concurrently; and the assault and battery conviction was placed on file with the defendant’s consent. The Appeals Court affirmed the aggravated rape conviction and reversed the kidnapping charge, set aside the kidnapping verdict and dismissed that indictment.1 Commonwealth v. Houston, 46 Mass. App. Ct. 378, 383 (1999). We granted the defendant’s application for further appellate review.
The defendant maintains that the judge erred when he prohibited the defendant from impeaching the rape victim with her five prior convictions for prostitution-related offenses. In Commonwealth v. Joyce, 382 Mass. 222, 231 n.8 (1981), the court left open the question whether, in a case like this, a defendant could introduce in evidence under G. L. c. 233, § 21, records of conviction of prostitution, or other sex-related crimes, to impeach a rape complainant’s credibility. We believe that, pursuant to the rape-shield statute, G. L. c. 233, § 21B, evidence of convictions of a rape complainant involving sexual conduct *618with others, including prostitution, is not generally admissible for the purpose of impeachment of the credibility of the testifying complainant, notwithstanding the provisions of G. L. c. 233, § 21.2 A complainant’s convictions involving sexual conduct could be admissible if they are relevant to motive to lie or bias, see Commonwealth v. Joyce, supra at 229, 231, or fall within the two statutory exceptions to the rape-shield statute. See G. L. c. 233, § 21B, and notes 7 & 8, infra.
I
The victim testified that in the early hours of July 2, 1995, she walked to a gasoline station in Brockton to buy cigarettes. The defendant drew his vehicle to within a couple of feet from her, and offered her a ride. When she declined, he grabbed her, pulled her into the vehicle, and, with a gun, threatened her with death if she tried to scream or flee. The victim testified he drove to an abandoned building on West Chestnut Street in Brockton, ordered her to undress, and threatened to cut off her clothes with his knife. The defendant forced her to perform oral sex on him, then raped her repeatedly, vaginally and anally, until approximately one hour after daybreak. She testified that she never had any conversation with the defendant about performing sexual acts with him for money.
The victim further testified that a few minutes after the defendant left her and drove away, as she walked down a nearby street, an unmarked police car pulled up to her and the officer asked her what had happened. She told the officer she had just been raped. Another officer who arrived on the scene testified that the victim was crying, confused, incoherent, and very upset. She was transported to a hospital by ambulance sometime around 6:30 a.m. The emergency room examining nurse observed fresh bruises on the victim, and testified that she was disheveled, rambling, crying, and upset.
In his testimony, the defendant admitted having oral and vaginal sexual intercourse with the victim from sometime after 1:30 a.m. that morning until sometime after 2 a.m. But he gave *619the following, very different account of the incident: He testified he was looking for a prostitute, as he had done in the past. After making eye contact with the victim at an intersection, she approached him in his car and offered to perform oral sex and have intercourse with him for $40. He suggested $30, which was agreed to. He testified the victim then directed him to drive to an abandoned building on West Chestnut Street where they had oral and vaginal intercourse until he told the victim to get out of the car. He refused to give the victim a ride home and an argument ensued. The defendant then pulled the victim out of the car by her arm. Before driving off, he pretended to give her $30, but in fact gave her only three dollars.
II
Prior to trial, the prosecutor filed a motion in limine to preclude defense counsel from impeaching the rape victim with her prior convictions for prostitution-related offenses. The motion also sought to obtain the judge’s permission to impeach the defendant with his prior conviction of indecent assault and battery.3
Defense counsel argued that evidence of the victim’s prostitution-related convictions did not fall within the rape-shield exclusion, see G. L. c. 233, § 21B, nor into the category of impermissible reputation or bad acts evidence. He argued the victim’s convictions were admissible because of the statutory provision allowing impeachment of a witness with prior convictions. See G. L. c. 233, § 21. He made no constitutional claim.4 The judge initially decided that the prostitution-related convictions would be admissible for impeachment purposes, despite the danger that the jury might use the convictions as propensity evidence concerning the victim, reasoning that the convictions showed the victim’s “supreme indifference” to conducting herself in accordance with law. However, when he learned that the prosecution intended to introduce the defendant’s prior conviction to impeach the defendant, the judge excluded evidence of both the defendant’s prior assault and battery conviction and the victim’s prior prostitution-related convic-*620tians. The judge did permit impeachment of the victim by means of her prior convictions for cocaine possession and a violation of a G. L. c. 209A protective order. Defense counsel objected immediately to the exclusion of the prostitution-related convictions.
At trial the victim’s estranged son testified that his mother had told him she had falsely claimed she was raped because a man had not paid her for an act of prostitution. He also stated that he did not know if his mother’s comment referred to the defendant or to someone else. The son was impeached with several prior convictions.5 Defense counsel did not object to this impeachment evidence, nor did he renew at that point his earlier objections to the exclusion of the victim’s prior prostitution-related convictions.
III
This case takes us into the ill-mapped area where the mandate to shield rape victims, see G. L. c. 233, § 21B, and the discretionary authority of judges to admit prior convictions to impeach witnesses, see G. L. c. 233, § 21, have unsettled or overlapping borders. The defendant argued that impeachment of the complainant with her five prior prostitution-related convictions was statutorily permissible.6 See G. L. c. 233, § 21. The Commonwealth argued that the judge should exercise his discretion to exclude the convictions and asserted that the convictions were excludable under the provisions of the rape-shield statute, G. L. c. 233, § 21B.7
*621A
We discuss first the mandate of the rape-shield statute, because the Commonwealth’s legitimate interest in protecting rape victims sets an important limit on a judge’s discretionary authority to admit prior convictions submitted generally to impeach a complainant witness. The rape-shield statute, G. L. c. 233, § 21B, prevents a defendant in a rape case who claims consent from putting the complainant on trial by raising collateral issues of little or no probative value concerning the complainant’s alleged predisposition for promiscuity.8 The statute governs the admissibility of evidence of the complainant’s sexual conduct with others and generally requires exclusion of this type of evidence, with several recognized exceptions. See G. L. c. 233, § 21B; Commonwealth v. Joyce, 382 Mass. 222, 225-229 (1981). We recently reaffirmed that “[t]he rape-shield statute is principally designed to prevent defense counsel from eliciting evidence of the victim’s promiscuity as part of a general credibility attack.” Commonwealth v. Pearce, 427 Mass. 642, 647 (1998), quoting Commonwealth v. Fitzgerald, 412 Mass. 516, 523 (1992). The policy rationale for this law is that evidence of the victim’s prior sexual conduct might divert attention from the alleged criminal acts of the defendant, inappropriately putting the victim on trial. See Commonwealth v. Joyce, supra at 227. Moreover, such evidence often has little relevance in rape cases where consent is the issue: the “victim’s *622consent to intercourse with one man does not imply her consent in the case of another.” Id., quoting Commonwealth v. McKay, 363 Mass. 220, 227 (1973). See Commonwealth v. Vanden-hecke, 248 Mass. 403, 404 (1924) (“[t]he rule is well established that the fact that a female witness is a prostitute ... is not admissible to impeach her”).
We have acknowledged, however, that evidence of the complainant’s prior sexual conduct may be admissible to show the complainant’s bias or motive to lie. See, e.g., Commonwealth v. Pearce, supra at 647-648; Commonwealth v. Stockhammer, 409 Mass. 867, 875-876 (1991); Commonwealth v. Domaingue, 397 Mass. 693, 699 (1986). The victim’s prior prostitution-related convictions were not admissible under that exception here because they were not submitted to show motive to lie. The defendant instead argued only generally that the convictions were relevant, as convictions, to impeach the victim’s credibility. Nonetheless, the defendant’s arguments touch closely, if not directly, on the victim’s possible motive to lie, and we find it necessary to discuss the possibility that her prostitution-related convictions were admissible as relevant to some motive to lie.
The circumstances of this case differ markedly from those in Commonwealth v. Joyce, supra, where we recognized error in the exclusion of evidence of prostitution charges relevant to a showing of bias or motive to lie. See id. at 223, 225-226, 231. In the Joyce case, the prostitution charges were relevant to whether the complainant might have had a motive to he about a rape. See id. at 224, 230. See also Commonwealth v. Elder, 389 Mass. 743, 750-751 (1983); Commonwealth v. Joyce, supra at 232 (Hennessey, C.J., concurring) (admissibility of prostitution charges confined to cases “where the disputed evidence is clearly relevant to a showing of bias or motive to lie by the complaining witness”). Cf. Commonwealth v. Allen, 29 Mass. App. Ct. 373, 375-376, 378-379 (1990). In the Joyce case, the complainant had been charged twice with prostitution — the second time when she had allegedly been discovered undressed in a car engaged in sexual acts. According to the account the defendant offered of the night of the alleged rape, he and the complainant were engaging in consensual sexual intercourse in his car when he saw a police cmiser approaching and told the complainant to get dressed. In offering the prior prostitution charges, the defendant “intended to show that the complainant, *623having been found in a similar situation on two prior occasions, had been arrested on each occasion and charged with prostitution.” Commonwealth v. Joyce, supra at 230. We consequently concluded that “[w]e cannot say that this [prostitution charge] evidence has no rational tendency to prove that the complainant was motivated falsely to accuse the defendant of rape by a desire to avoid further prosecution” (emphasis added). Id.
In contrast, the defendant here has presented no particular circumstances involved in the victim’s prior prostitution convictions that would point to a motive to he about the rape. When the police arrived, the victim was clothed and alone; she was not discovered in a compromising position. There is also no suggestion here that the victim feared she might again be arrested for prostitution if she did not fabricate a rape complaint. Cf. Commonwealth v. Joyce, supra at 230. There was no basis for admitting the victim’s prostitution convictions as relevant to a motive to lie.
B
We now consider whether the victim’s prostitution-related convictions should have been admitted pursuant to G. L. c. 233, § 21. Evidence of prior convictions may be admissible to impeach any witness where the convictions meet the statutory provisions of § 21. See Commonwealth v. Drumgold, 423 Mass. 230, 249 (1996); Commonwealth v. Maguire, 392 Mass. 466, 470 (1984). The rationale is that “a defendant’s earlier disregard for the law may suggest to the fact finder similar disregard for the courtroom oath.” Commonwealth v. Drumgold, supra, quoting Commonwealth v. Fono, 400 Mass. 296, 302-303 (1987). Admission of evidence of prior convictions of a witness for impeachment purposes is at the discretion of the trial judge.9 See G. L. c. 233, § 21; Commonwealth v. Maguire, supra at *624470. The judge must balance the danger of unfair prejudice against the probative value of the evidence for the purpose of impeachment. See Commonwealth v. Drumgold, supra at 249.
There is potential conflict between the application of G. L. c. 233, § 21, and the rape-shield statute, § 21B, in the handling of prior prostitution convictions submitted to impeach the complaining witness’s credibility in a rape trial. Section 21 apparently gives a judge discretionary authority to admit such convictions, whereas § 21B, read literally, would generally bar their admission.10 The legislative intent behind the later-enacted rape-shield provision, § 21B, is not definitive concerning whether it was meant to modify the application of § 21 when rape trials are involved.11 See Joyce, supra at 228 & n.6, citing Bumim, Massachusetts Rape-Shield Law — An Over-Step in the Right Direction, 64 Mass. L. Rev. 61, 63 (1979) (discussing legislative history of rape-shield statute and noting it “is limited”).
Four alternative versions of the bill that eventually became the rape-shield statute expressly provided that the shield provisions were not meant to limit the right to impeach credibility of the victim by use of prior convictions, but this language was dropped in the legislation that was enacted.12 See 1977 . House Doc. No. 4133; 1977 House Doc. No. 2586; 1977 House Doc. *625No. 2228; 1976 Senate Doc. No. 678. See also Bumim, supra at 64-65. Compare G. L. c. 233, § 21B, with 1977 Senate Doc. No. 1433. The fact the Legislature dropped language expressly allowing admission of prior convictions of the complainant suggests the Legislature did not want such convictions to be admissible for the impeachment of a rape complainant’s credibility. Moreover, the legislative purpose of the rape-shield statute is to protect rape victims. See, e.g., St. 1977, c. 110, Preamble (arguing for the smallest number of judicially recognized exceptions to its general bar on admission of evidence of the victim’s sexual conduct).
In his concurrence, Justice Lynch suggests that our view “amounts to an implied repeal” of G. L. c. 233, § 21. We do not agree. The later enacted rape-shield statute addresses the admissibility of a special category of evidence, a complaining witness’s prior sexual conduct, while G. L. c. 233, § 21, is framed in very general terms. Our conclusion reads the two statutes harmoniously. However, to the extent a conflict between the two statutes exists, “the more specific statute controls over the more general one.” See 2B Singer, Sutherland Statutory Construction § 51.02 (5th ed. 1992). Finally, § 21 significantly predates the rape-shield statute. See note 11, supra. If provisions of those two statutes are irreconcilable, the later enacted rape-shield provision should control. See id.
We conclude that the rape-shield provisions excluding most evidence of the complainant’s sexual conduct were intended to exclude this kind of evidence even when it involves the complainant’s convictions submitted to impeach the complainant’s credibility generally. Thus, despite G. L. c. 233, § 21, the trial judge generally does not have discretion to admit such convictions. A contrary rule, allowing a judge discretion on the point, infuses a substantial measure of illogic into the logical and fair conclusion that follows from reflection on the purposes of the rape-shield statute and the import of the court’s statements in Commonwealth v. McKay, 363 Mass. 220, 227 (1973), and Commonwealth v. Vandenhecke, 248 Mass. 403, 404 (1924), *626among others. Our conclusion takes into account that the need to exclude evidence of prostitution or prostitution-related convictions should not be overridden by a theoretical argument that the evidence may be admissible under G. L. c. 233, § 21 (but not under the rape-shield statute), because the statutes have different purposes. Surely, a jury, no matter how much effort the judge makes to purge their mindsets by admonitory instructions, are more likely to conclude that the impeaching convictions show that the complainant should not be believed, not because she is untruthful, but because she has been, and thus continues to be, indiscriminate in sexual relations.13
A complainant’s convictions involving sexual conduct could be admissible if they are clearly relevant to a motive to lie or to bias, see Commonwealth v. Joyce, supra at 229, 231, or fall within the two statutory exceptions of the rape-shield statute. See G. L. c. 233, § 21B. In this case, evidence of the prostitution-related convictions of the complainant did not fall into any of these exceptions, and was properly excluded.
The Appeals Court dismissed the kidnapping conviction as duplicative of the aggravated rape conviction in the circumstances of the case. Commonwealth v. Houston, 46 Mass. App. Ct. 378, 383 (1999).
In Commonwealth v. Joyce, 382 Mass. 222, 231 (1981), we emphasized that prostitution was not, itself, relevant to credibility. Our views here are consistent with the holding in that case. There, unlike here, evidence involving charges of the complainant’s prior prostitution was admissible because it clearly touched on her possible motive to lie, not on her general credibility. See id. at 224-226, 230-231.
The motion requested in the alternative that the defendant’s and the victim’s prior convictions be either both allowed or both precluded.
Because the defendant raised no constitutional objection at trial, we decline to address the constitutional argument he made on appeal. See, e.g., Commonwealth v. Pares-Ramirez, 400 Mass. 604, 609 (1987).
The son’s convictions were of breaking and entering in the nighttime with intent to commit a felony, breaking and entering in the daytime to commit a misdemeanor, breaking and entering in the daytime with intent to commit a felony, and two convictions of larceny of property.
General Laws c. 233, § 21, begins: “The conviction of a witness of a crime may be shown to affect his credibility ....’’
General Laws c. 233, § 21B, provides in relevant part:
“Evidence of specific instances of a victim’s sexual conduct in such an investigation or proceeding shall not be admissible except evidence of the victim’s sexual conduct with the defendant or evidence of recent conduct of the victim alleged to be the cause of any physical feature, characteristic, or condition of the victim; provided, however, that such evidence shall be admissible only after an in camera hearing on a written motion for admission of same and an offer of proof. If, after said hearing, the court finds that the weight and relevancy of said evidence *621is sufficient to outweigh its prejudicial effect to the victim, the evidence shall be admitted; otherwise not.”
The common law of Massachusetts has also long held evidence of instances of a complainant’s sexual conduct with others to be inadmissible in such rape proceedings. See, e.g., Commonwealth v. Domaingue, 397 Mass. 693, 698 (1986) (at common law, evidence of prior sexual conduct of victim with persons other than defendant inadmissible to impeach victim’s credibility); Commonwealth v. Elder, 389 Mass. 743, 751 n.12 (1983), and cases cited; Commonwealth v. Regan, 105 Mass. 593, 594 (1870).
The rape-shield statute applies to trials and proceedings for a violation of, inter alla, G. L. c. 265, § 22. See G. L. c. 233, § 21B. The defendant’s trial for aggravated rape came under the provisions of the rape-shield statute, and evidence of the victim’s prior sexual conduct with others generally would be statutorily excluded, unless governed by a recognized exception, such as evidence showing bias or motive to lie. The rape-shield law statutorily recognizes two exceptions where specific instances of the victim’s sexual conduct are admissible: (1) where the conduct was with the defendant, and (2) where the conduct is alleged to be the cause of a condition of the victim. See G. L. c. 233, § 21B. Neither of these exceptions applies in this case.
In Commonwealth v. West, 357 Mass. 245, 249 (1970), we held that G. L. c. 233, § 21, gave judges no discretion to exclude such prior convictions. We overruled West in Commonwealth v. Maguire, 392 Mass. 466, 470 (1984), and recognized the discretion of judges to exclude prior conviction impeachment evidence. We did so in the context of a prior conviction of a defendant. Id. at 469-470. Our language suggested, without expressly holding, that this discretion also applied to witnesses other than defendants. Id. at 470. Judicial discretion to admit or exclude prior convictions of any witness submitted for impeachment purposes is clearly consistent with the statutory language. See G. L. c. 233, § 21 (conviction “of a witness . . . may be shown” [emphasis added]); Commonwealth v. Drumgold, 423 Mass. 230, 249 (1996); Com*624monwealth v. Maguire, supra; Commonwealth v. Bucknam, 20 Mass. App. Ct. 121, 123-124 (1985). See also Commonwealth v. Burnett, 417 Mass. 740, 743 n.l (1994), citing Commonwealth v. Bucknam, supra (we have not adopted role that would provide that judge does not have discretion to exclude evidence of conviction of witness other than defendant). But see Proposed Mass. R. Evid. 609 (a), quoted in Commonwealth v. Maguire, supra at 469 n.7 (there “shall be no discretion to exclude” prior conviction offered to impeach witness who is not the accused).
Our decision in Commonwealth v. Joyce, 382 Mass. 222 (1981), did not resolve this issue in favor of admissibility of such convictions under § 21, see Commonwealth v. Houston, 46 Mass. App. Ct. 378, 381 (1999), because in Joyce we faced the question of prostitution charges against the rape complainant admissible to show possible bias or motive to lie, not convictions admitted to impeach credibility generally. See Commonwealth v. Joyce, supra at 224 & n.2, 225-227, 231.
Section 21B was enacted in 1977. St. 1977, c. 110. Section 21 significantly predates § 21B. Rev. St. (1836) c. 94, § 56.
1977 House Doc. Nos. 2228 and 2586 both contained the following language: “Nothing in this section shall limit the right of either the state or the accused to impeach credibility by the showing of prior felony convictions.” 1977 House Doc. No. 4133 and 1976 Senate Doc. No. 678 similarly provided that certain evidence would remain admissible under their rape-*625shield provisions, including “evidence of conviction of a crime of the victim, solely to impeach her credibility.” In contrast, 1977 Senate Doc. No. 752, and the bill that was finally enacted as the rape-shield statute, 1977 Senate Doc. No. 1433, did not contain the exception allowing evidence of convictions of the victim for impeachment purposes. See Commonwealth v. Joyce, supra at 228 n.6 (discussing bills considered); 1977 Senate J. 102, 375-376, 399, 423 (giving procedural history of 1977 Senate Doc. No. 1433).
We cannot agree with the defendant’s assertion that rape complainants are, in effect, “[ojrdinary witnesses” who cannot be prejudiced by the admission of prior convictions in a manner similar to that risked by defendants. While the risk of prejudice is not the same for the rape complainant as for the defendant, the rape complainant faces dangers of harassment and unnecessary invasions of privacy different from an ordinary witness, a difference justifying the need for heightened protection of the complainant’s interests. See, e.g., Michigan v. Lucas, 500 U.S. 145, 149-150 (1991); G. L. c. 233, § 21B.