Wе granted the defendant’s application for further appellate review to consider his claim that the trial judge committed reversible error by admitting expert testimony that deoxyribonucleic acid (DNA) tests could not exclude the defendant as the source of DNA taken from the scene of the crime without accompanying testimony explaining the statistical import of those results. 1 The defendant also claims that there was insufficient evidence to convict him of home invasion and assault by means of a dangerous weapon because the duct tape used in the attack was not a “dangerous weapon” 2 ; that his constitutional *842 rights to confrontation were impermissibly restricted when the judge limited the scope of certain cross-examination; and that he received ineffective assistance of counsel. 3 We reject the defendant’s sufficiency of the evidence claim. We conclude, however, that expert testimony that DNA tests could not exclude the defendant as a potential source of DNA found at the crime scene, absent testimony regarding statistical findings explaining the import of such a result, was likely to confuse and mislead the jury such that any probative value of the test results was substantially outweighed by their prejudicial effect. Because the error in admitting such evidence was prejudicial, we remand for a new trial and provide guidance on issues that may then arise.* ** 4
1.
Facts.
The facts as they properly could have been found by the jury are set forth in the decision of the Appeals Court,
Commonwealth
v.
Mattei,
At approximately 1 p.m., on April 26, 2002, the thirty-six year old victim returned to her apartment in a housing complex operated by the Andover Housing Authority (housing authority). As she walked down the stairs to her basement apartment, she saw the defendant — a man she did not recognize — mopping the floor in the basement hallway. After a brief exchange, the victim entered her apartment, locking the door behind her. Shortly thereafter, through the locked door, 5 the defendant warned her to be careful if she left the apartment because the floor in the hall was wet and slippery.
One to five minutes later, while she was standing near her *843 bed facing away from her front door, a man grabbed the victim from behind. A struggle ensued, during which the assailant repeatedly pressed his hand over the victim’s mouth and nose, making it difficult for her to breathe. During the struggle the assailant tried to place duct tape over the victim’s mouth, 6 but was unsuccessful in doing so. Eventually, as she testified, the victim could struggle no more. The assailant then attempted to rape the victim anally, but stopped after ten or fifteen minutes and left the apartment. The victim was unable to see the assailant’s face, and could not identify her attacker. She later described the assailant as “white,” 7 and reported that he was wearing a white or light gray sweatshirt.
2.
Sufficiency of the evidence.
The defendant argues that the judge erred in denying his motion for required findings of not guilty of home invasion and assault by means of a dangеrous weapon because the jury could not properly have found that the duct tape as used by the assailant was a “dangerous weapon” within the meaning of those statutes.
8
See
Commonwealth
v.
Doucette,
We agree with the Appeals Court that resolution of this claim is determined in large part by
Commonwealth
v.
Cruz,
Our reliance on
Commonwealth
v.
Cruz, supra,
is based not entirely on the fact that the object at issue here, as in that case, is duct tape. As we noted in
Commonwealth
v.
Appleby, supra
at 307 n.5, the use of a particular object in one case “should not be construed to mean that any intentional unjustified touching with an object previously held in a different case to have been
capable
of being a dangerous weapon constitutes a crime .... A reasonable jury might well reach a different conclusion as to [an object] when used in different circumstances.” (Emphasis in original.) Thus the “essential question” is “whether the object, as used by the defendant, is capable of producing serious bodily harm.”
Commonwealth
v.
Tevlin,
That the victim in this case did not die or suffer serious bodily harm from the attempted use of the duct tape to cover her mouth is not dispositive.
11
The “relevant behavior” for the offense of assault by means of a dangerous weapon “is an outward demonstration of force,” and requires “only apparent ability to injure.”
Commonwealth
v.
Appleby, supra
at 305, citing
Commonwealth
v.
Henson,
3. Admissibility of evidence that defendant could not be excluded by a DNA test without accompanying statistics. The defendant argues that it was error to admit expert testimony that the defendant could not be excluded as a potential source of DNA found on the interior doorknob of the victim’s apartment, and that the victim could not be excluded as a potential source of DNA found on the defendant’s sweatpants, without accompanying testimony explaining the statistical relevance of those nonexclusion results. For the reasons that follow, we agree. 13
At trial, the Commonwealth presented expert testimony from a forensic chemist from the DNA unit at the State police crime *847 laboratory, who testified that she had conducted DNA tests on various pieces of evidence collected from the crime scene. The test results fell intо two groups: tests of DNA taken from a sweatshirt showed a “match” with DNA samples from the defendant and the victim; 14 other tests did not result in “matches” but “[could not] .exclude” the defendant or the victim as a possible contributor to the sample. There were no “matches” between the defendant and DNA from any samples taken from inside the victim’s apartment, and there were no matches between the victim and DNA from samples taken from the defendant’s clothes when apprehended.
Turning to the evidence of a “match,” the expert first testified, without objection, that DNA from a sample taken from the sleeve of a white sweatshirt found in a trash barrel in the basement laundry room across the hall from the victim’s apartment “matched” the DNA in a sample taken from the victim, and that DNA from a sample taken from the front of the sweatshirt “matched” the DNA in a sample taken from the defendant. 15 The expert explained that the DNA tests she used assigned numbers to particular locations, or allele sites, on the DNA molеcule belonging to the profile being tested. 16 A “match” occurred when the results from all thirteen allele sites and a gender test in the two samples being compared were identical. The expert further testified as to the probability that a randomly selected member of *848 the population would have a DNA profile that “matched” the DNA profiles in the samples from the sweatshirt. 17 The defendant does not challenge the “match” testimony.
The defendant’s challenge focuses on the expert’s testimony concerning two other samples, one taken from the defendant’s sweatpants and the second from an interior doorknob within the victim’s apartment. As to the sample taken from the defendant’s sweatpants, the expert first testified that this was a “mixture” that contained DNA from at least two sources. 18 Over the defendant’s objection, the expert then testified that the victim was “included” or “could not be excluded” as a potential source of DNA in the sample taken from the defendant’s sweatpants. 19 As to the swabbing of blood found on the interior doorknob of the door to the victim’s apartment, the expert testified that this also showed the presence of DNA from more than one source, and a DNA test showed the mixture was “consistent with” DNA from the victim and from the defendant. According to the expert, the victim and the defendant were both “included” as “potential contributor[s]” to the mixture, i.e., neither the victim nor the defendant “were excluded as a potential contributor to the DNA mixture on the interior of the doorknob.” 20 The expert explained that a result that certain profiles were “not excluded” meant that *849 “the numbers that are present in those profiles are also present in the [sample profile] being compared.” The nonexclusion results here were not “matches,” she explained, because either not enough DNA was available to test all thirteen allele sites or it was not possible to distinguish the major from the minor profile at one allele site. 21 , 22 The expert did not testify as to the probability that an individual randomly selеcted from the population would also “not be excluded” by these tests, nor did she provide any other indication as to the meaning of a “not excluded” result. She merely displayed charts to the jury illustrating the numerical results of the tests at each tested location and stated generally that the alleles at the sites she tested “are extremely variable between people.” 23
*850
We now consider the defendant’s objection to this testimony. A judge generally is accorded substantial discretion in deciding whether evidence is relevant, and if so, whether it nevertheless should be excluded as less probative than prejudicial. See
Commonwealth
v. Mathews,
We have also held that in a criminal trial we will “not permit the admission of test results showing a DNA match (a positive result) without telling the jury anything about the likelihood of that matсh occurring.”
Commonwealth
v.
Curnin,
The same reasoning applies to evidence that a DNA test, although resulting in less than a complete “match,” could not exclude a particular individual as a potential contributor.
25
,
26
*852
Without reliable accompanying evidence as to the likelihood that the test could not exclude other individuals in a given population, the jury have no way to evaluate the meaning of the result.
27
As the dissent in
Commonwealth
v.
Mattei,
Further, admitting evidence of a failure to exclude without accompanying evidence that properly interprets that result creates a greater risk of misleading the jury and unfairly prejudicing the defendant than admission of a “match” without accompanying statistics. As to “matches,” it is “generally well known that DNA testing often allows scientists to identify a particular individual from among millions.”
Peters
v.
State,
The Commonwealth’s reliance on
Commonwealth
v.
Mathews,
The Commonwealth’s reliance on
Commonwealth
v.
McNickles,
The challenged expert testimony concerning the nonexclusion results should not have been admitted without accompanying statistical explanation of the meaning of nonexclusion. We therefore must determine whether the error “did not influence the jury, or had but very slight effect,” in other words whether we can say, “with fair assurance, after pondering all that happened without stripping the erroneous action from the whole, that the judgment was not substantially swayed by the error.”
Commonwealth
v.
Flebotte,
The error was prejudicial. First, the prosecutor emphasized the importance of the nonexclusion DNA evidence in her closing argument. She described the evidence as “very important in this case.” It “create[d] links in the chain,” and “help[ed] to put all of those pieces of other evidence together,” into “a big, clear picture.” The prosecutor specifically encouraged the jury to “draw an inference” from the evidence that the defendant could not be excluded as a potential source of DNA on the doorknob inside the victim’s apartment that the defendant was *856 “in fact, the assailant in this case.” 33 She pointed specifically to the “different areas of concordance” linking the defendant to the interior doorknob. Her emphasis on the doorknob DNA was hardly surprising, as no other evidence placed the defendant inside the victim’s apartment; the victim twice told the dispatcher in her 911 call that she had locked her door; the defendant did not have a key to the apartment; 34 and there were no signs of a break-in. The prosecutor focused on the nonexclusion of the victim as a potential source of DNA on the defendant’s sweatpants, telling the jury that the DNA profile found on the sweatpants was “consistent at numerous locations on the DNA with [the victim’s] DNA profile.” Her emphasis on this evidence is similarly unsurprising, as no other evidence linked the victim to the defendant through clothing that the defendant was wearing when apprehended. Cf. note 16, supra. That linkage was crucial to the Commonwealth’s case because the victim could not identify her assailant. The Commonwealth concedes in its brief that the nonexclusion DNA results were the “most damaging” DNA results for the defense.
The lack of statistical evidence concerning the nonexclusion test results was particularly harmful to the defendant because the prosecutor, in effect, encouraged the jury to act as their own experts, arguing to them that the results from tests of the defendant’s sweatpants (which could not exclude the victim as a potential contributor) were “consistent” at “numerous locations on the DNA” with the victim’s DNA profile. “You can look at that chart,” she said, “and you can think about what that means, when you analyze the evidence. Those were the defendant’s sweatpants.”
The “matches” between DNA from both the defendant and the victim and DNA samples on the sweatshirt discovered by the police in the trash barrel outside the victim’s apartment does not mandate a contrary result. The defendant’s DNA could have *857 been deposited on the sweatshirt before the attack (there was testimony that he had beеn given the sweatshirt earlier in the week). Although there was testimony that the defendant had been seen wearing the sweatshirt on the morning of the attack, there was also testimony that a photograph from a bank surveillance camera showed the defendant later that morning, before the attack, without the sweatshirt. We therefore cannot say that the jury were not substantially swayed by the nonexclusion DNA results into discounting the possibility that someone other than the defendant wore the sweatshirt during the attack. 35 A new trial is warranted.
4. Limit on cross-examination. Because a similar issue may recur at any new trial, we address the defendant’s claim that his rights to confront witnesses under the Sixth Amendment to the United States Constitution and art. 12 of the Declaration of Rights of the Massachusetts Constitution were violated by limitations placed by the judge on his cross-examination of certain witnesses. The defendant was one of four inmates from the Correctional Alternative Center in Lawrence assigned to work that day doing maintenance and cleaning for the housing authоrity. At trial, the defendant sought to show that the police had focused on him prematurely because he was a convict on work release, and that the police had conducted a flawed investigation by failing to fingerprint, conduct DNA testing, or investigate the background of three employees of the housing authority, two of whom had significant criminal records. 36 The judge permitted defense counsel to elicit from the investigating police officers that they had not asked the housing authority employees whether they had *858 criminal records, that they had not run criminal background checks on the employees, and that the lead police investigator had learned only after the investigation that two of the employees had criminal records. The judge did not allow defense counsel to ask the officers whether it would have been important to them to know that one housing authority employee had been convicted of murder in the second degree and another charged with аggravated rape. 37
Both the Sixth Amendment and art. 12 “guarantee a criminal defendant’s right to confront the witnesses against him through cross-examination.”
Commonwealth
v.
Farley,
One focus of the defense was on the inadequacy of the police investigation, and we have concluded that, in such circumstances, a limitation on cross-examination such as occurred here is not proper. See
Commonwealth
v.
Miles, supra
at 72-73. In that case, we concluded that a restriction on the defendant’s cross-examinatian of the police about their “investigation of other suspects”
38
was error because “testimony about the police investigation that led to the defendant’s arrest” after an attack in which the victim did not see her assailant’s face was “highly material to one of the most important issues at trial, the identification of the defendant as the perpetrator of the crimes.”
Id.
at 72, 73 n.1. We recognize that the judge in this case did accommodate in part the defendant’s “legitimate purpose in seeking to inquire about other suspects.”
Id.
at 72.
39
Nevertheless, the judge’s refusal to permit
*859
the defendant to question
the police
about their knowledge of the criminal histories of the housing authority employees denied the defendant the opportunity to show that a central defense — that the police investigation was inadequate in that the police prematurely focused on him to the exclusion of investigating other potential suspects — was not based purely on speculation. The limitations prevented the defendant from establishing that the housing authority employees — Dion in particular — may have had an incentive to misdirect the police during the investigation to deflect attention away from themselves.
40
Dion and Roman both gave their names and dates of birth to police at the outset of the investigation. It would be reasonable to infer that each knew it was likely that the police could learn of their criminal records, that each may have feared becoming a suspect in the investigation, and that each may have had an incentive to deflect police
*860
attention away from himself during the immediate investigation. Cf.
Commonwealth
v.
Graziano,
5.
Ineffective assistance of counsel.
The defendant claims ineffective assistance of counsel because trial counsel failed to “seek either dismissal of the charges or some other appropriate remediation” for the Commonwealth’s failure to take possession of a roll of duct tape found in the victim’s bedroom, an omission that the defendant claims constituted a loss of potentially exculpatory evidence. We agree with the Appeals Court that the “situation was not one calling for sanctions,” and that the defendant was not deprived of effective assistance of counsel.
Commonwealth
v.
Mattei,
6. Conclusion. For the foregoing reasons, the defendant’s convictions cannot stand. The judgments are reversed, the verdicts are set aside, and the cases are remanded to the Superior Court for a new trial.
So ordered.
Notes
The defendаnt was found guilty by a jury of home invasion, in violation of G. L. c. 265, § 18C; breaking and entering with intent to commit a felony, in violation of G. L. c. 266, § 17; assault with intent to rape, in violation of G. L. c. 265, § 24; indecent assault and battery on a person fourteen years of age or older, in violation of G. L. c. 265, § 13H; and assault by means of a dangerous weapon, in violation of G. L. c. 265, § 15B
(b).
The defendant was also found guilty of assault and battery, in violation of G. L. c. 265, § 13A; that indictment was placed on file with the defendant’s consent. The Appeals Court affirmed.
Commonwealth
v.
Mattel,
The home invasion statute, G. L. c. 265, § 18C, provides: “Whoever knowingly enters the dwelling place of another knowing or having reason to know that one or more persons are present within or knowingly enters the dwelling place of another and remains in such dwelling place knowing or having reason to know that one or more persons are present within while armed with a dangerous weapon, uses force or threatens the imminent use of force upon any person within such dwelling place whether or not injury occurs, or intentionally causеs any injury to any person within such dwelling place shall be punished by imprisonment in the state prison for life or for any term of not less than twenty years” (emphasis added).
The statute prohibiting assault by means of a dangerous weapon, G. L. *842 c. 265, § 15B (b), provides: “Whoever, by means of a dangerous weapon, commits an assault upon another shall be punished by imprisonment in the state prison for not more than five years or by a fine of not more than one thousand dollars or imprisonment in jail for not more than two and one-half years” (emphasis added).
The Appeals Court rejected the defendant’s arguments concerning a recording of a 911 telephone call made by the victim that was admitted in evidence and played for the jury. See Commonwealth v. Mattei, supra at 513-514. The defendant does not pursue those claims before this court.
We acknowledge the amicus curiae brief filed by the Committee for Public Counsel Services.
There was testimony that would permit the jury to infer that the victim had failed to lock the door properly on this occasion. There was also evidence that cеrtain employees of the Andover Housing Authority (housing authority) had “master” keys that could open her apartment door.
Two pieces of duct tape found at the scene were admitted in evidence. The duct tape was two to two and one-half inches wide.
The victim described her attacker as “white” and “Caucasian,” but also said that he “may or may not have been Spanish.” During the voir dire of the jurors, the judge described the defendant as Hispanic, and defense counsel stated in his opening statement that the defendant was Hispanic. At trial there was no testimony as to the defendant’s ethnicity. See note 17, infra.
The defendant argues that “there was only a single attempt to place one piece of tape across only the mouth of the victim, and no attempt to replace it when it fell off.” The defendant also argues that the victim was not “bound by tape,” that there was “no attempt to wrap the tape around the victim’s mouth,” and that the victim was “not threatened with the tаpe, nor did she hear it being ripped prior to its use.”
The judge denied the defendant’s motion for required findings of not guilty on all counts at the close of the Commonwealth’s case, and the defendant’s renewed motion at the close of the evidence. The defendant challenges here only the denial of his motions for a required finding as to his convictions of home invasion and assault by means of a dangerous weapon.
The defendant does not challenge the instructions.
The defendant argues that no Massachusetts case concerning home invasion has upheld a conviction “on the basis of a neutral object serving as a dangerous weapon where the object was not used to cause serious harm to a victim.” The defendant’s focus is misplaced. He cites to no case, and we are aware of'none, where the issue was
not
submitted to the jury. Cf.
Commonwealth
v.
Howard,
The “meaning of ‘dangerous weapon’ depends to a certain extent on the context in which it is used.”
Commonwealth
v.
Appleby,
Contrary to the Commonwealth’s claim, the objection was preserved at trial. Defense counsel objected to the expert witness’s testimony regarding nonexclusion results, arguing that testimony that a DNA test “cannot exclude” the defendant “would be too confusing to this jury. They may use the failure *847 to exclude as inculpatory of Mm when that is not. . . .” Defense counsel did not argue explicitly that the nonexclusion results would be too confusing because they were not accompamed by statistical evidence to explain their import, but the defendant’s claim to that effect on appeal was fairly encompassed by his objection at trial.
There were other “matches” to the victim’s DNA on a mattress and two cuttings from a bedspread in her apartment; and there was a “match” to the defendant’s DNA on the T-shirt he was wearing when he was arrested. Those “matches” are not at issue in tMs appeal.
A housing authority employee identified the sweatshirt as one he had given to the defendant earlier in the week. The defendant had been seen wearing the sweatsMrt the morning of the attack, but he had also been seen later that same morning, before the attack, without the sweatsMrt.
The expert explained that each location on an mdividual’s DNA molecule has two alleles. The test results thus show two numbers for each location, each number representing one of the alleles. For descriptions of DNA testing, see
Commonwealth
v.
Rosier,
The expert testified that the probability of a randomly selected person having a DNA profile that, like the victim’s, matched the profile of the DNA in the sample from the sweatshirt sleeve was one in 1.373 quadrillion for the Caucasian population, one in 135.9 quadrillion for the African-American population, and one in 662.3 quadrillion for the Hispanic population. The probability of a randomly selected person having a DNA profile that, like the defendant’s, matched the profile of the DNA in the sample from the sweatshirt front was one in 631.7 quadrillion for the Caucasian population, one in 5.152 quintillion for the African-American population, and one in 13.51 quintillion for the Hispanic population.
The expert testified that the tests she used could distinguish between profiles in a mixture because one contributor (the major profile contributor) contributed more DNA to the mixture than the other contributor (the minor profile contributor).
The expert testified that the victim was “included as a potential source of the major female profile in the DNA mixture.” When asked by the prosecutor if “it would be fair to say that [the victim] could not be excluded as a source of that profile,” the expert responded, “That’s correct.”
Again, the expert used the term “included” in her testimony, and then answered affirmatively when asked by the prosecutor whether it was “fair to say” that neither the victim nor the defendant “were excluded.” See note 19, supra.
The expert testified that the results of the test of the swab of the interior doorknob showed that at all thirteen tested allele sites, and at the gender site, the major profile in the swab was “concordant with” the defendant’s profile, and the numbers at each allele site in the victim’s profile were “represented” in the minor profile. However, at one allele site the major and minor profiles in the swab could not be distinguished. Concerning the expert’s use of the term “concordant with,” see note 23, infra.
There was some inconsistency in the expert’s testimony regarding the results of the test of the sample from the defendant’s sweatpants. During direct examination, the expert testified that she tested the DNA from the sweatpants at only nine allele sites plus the gender site, because only “a small amount of DNA . . . was extracted from the sample.” Further, according to the expert there was not enough DNA from the minor profile contributor in the sample to be able to compare that profile to a known exemplar. On redirect, however, the expert testified that she tested thirteen allele sites on the sweatpants, found twelve “consistent” with the victim’s DNA profile, and could not distinguish the major and minor profiles at one allele site.
The charts submitted in evidence suggest that the expert’s initial testimony was correct, and that she mistakenly testified as to the results from the doorknob swab on redirect when she was in fact being questioned about the sweatpants. In an appendix, the Commonwealth’s brief reproduces the charts that were submitted in evidence, together with an affidavit of the assistant district attorney that the reproductions are identical to the charts that were used at trial. The defendant makes no objection to our consideration of the reproductions.
The expert distinguished nonexclusion results from “inconclusive” results. For example, while the victim “could not be excluded” as a potential source of the major DNA profile found on the defendant’s sweatpants, there was not enough DNA from the minor profile contributor in that sample to be able to compare that profile to the defendant’s, or anyone else’s, DNA profile. Thus, “the minor profile in the DNA mixture yielded inconclusive results for comparison with” the defendant (emphasis added); in other words, according to the expert, as to the minor profile in the sample, “there has been no conclusion made.”
At various points in her testimony, the expert used the word “concordant” *850 to describe both a “match” and a result of “not excluded.” The expert stated that “the samples that are concordant with [the known sample from the defendant] . . . include the sweatshirt front" (a match); “the numbers [on the profile from the sweatpants] are concordant with [the victim’s] profile” (a nonexclusion); and the results from the doorknob swab are “concordant” with the defendant’s profile (a nonexclusion). The expert earlier testified that “checking] for concordance” between the two profiles being compared in a DNA test means “seepng] if there is a match between all the locations, from the evidence profile and the known profile” (emphasis added).
As to
inconclusive
results, in
Commonwealth
v.
Curnin,
With the exception of the jurisprudence of the State of Washington, see
State
v.
Bander,
Other jurisdictions that have rejected claims that DNA test results should not be admitted without accompanying statistics have similarly not distinguished between tests resulting in a “match” and those resulting in a failure to exclude. See
State
v.
Boles,
In
Commonwealth
v.
Gaynor,
The Commonwealth argues that requiring the presentation of statistical analysis as an accompaniment to testimony that DNA test results could not exclude an individual as a potential source “could prove highly damaging to defendants as a class,” given advancements in technology allowing results short of a complete “match” nevertheless to be strongly discriminating among potential contributors. There is nothing in the record to support the claim, and our own precedents reveal that not all DNA tests result in extremely low random match probabilities. See, e.g.,
Commonwealth
v.
O’Laughlin,
The Commonwealth’s expert in this case distinguished between nonexclusion and inconclusive results, using the term “inconclusive” the same way the term was used in
Commonwealth
v.
Mathews,
Some confusion may have been caused by our use of the term “inconclusive” in, for еxample,
Commonwealth
v.
O’Laughlin, supra
at 208, and
Commonwealth
v.
Benoit,
In
Commonwealth
v.
Nesbitt,
In Commonwealth v. McNickles, supra, the Commonwealth’s expert testified that tests showed that the contributor to DNA taken from swabs from a rape victim was homozygous at a particular allele site (i.e., that each of the contributor’s two alleles at that site were identical). See id. at 851. The defendant challenged the reliability of the underlying technology and the reliability of the results because the sample size was too small. See id. at 849. The defendant also presented an expert who testified that the test did not show that the contributor was homozygous, but who agreed that the test showed that “at least one of the contributor’s alleles at that site was a 4.2/3, and that the defendant therefore could not be excluded.” Id. at 852. We concluded that the test results were relevant and admissible, even if the defense expert’s view were accepted, because “the test still provided descriptive information about the perpetrator.” Id. at 854.
The prosecutor encouraged the jury to look at the charts showing the non-exclusion results, which were in evidence, and to “see how those numbers line up.”
As the defendant points out, while there was uncontroverted evidence that the defendant had been outside the apartment immediately before the attack, there was also uncontroverted evidence that at least two housing authority employees were in the vicinity, one of whom had a master key and both of whom had criminal records.
The Commonwealth argues that there can be no prejudice because the defendant “has avoided every opportunity to bring to light what the relevant statistics would or might be,” and thus this court may infer that any such statistics would be “highly unfavorable” to him, citing
Commonwealth
v.
Little,
Francisco Roman was convicted in Puerto Rico of murder in the second degree in 1995. Robert Dion was charged with aggravated rape in 1986 in Essex County, and ultimately pleaded guilty to the lesser included offense of assault and battery. The judge permitted the jury to consider Francisco Roman’s conviction in their evaluation of his credibility as a witness.
The judge did not permit defense counsel to elicit Robert Dion’s criminal history.
In
Commonwealth
v.
Miles,
The judge permitted the defendant to establish that the police did not investigate the criminal backgrounds of other individuals working at the hous *859 ing complex on the day of the attack and to establish that, unknown to the investigating police, two of the three housing authority employees working there on the day of the assault did in fact have criminal records. Although the jury also learned that one of those employees, Francisco Roman, had been convicted of murder in the second degree, the judge instructed the jury that the stipulation of the parties as to Roman’s conviction was admitted “solely insofar as it affect[ed] his credibility” as a witness, and therefore could not be considered by the jury on the defense of an inadequate police investigation.
We reject the defendant’s argument that evidence of Dion’s criminal records was admissible to show the potential for bias in his testimony at trial. Defense counsel conceded that Dion’s conviction of assault and battery in 1986 was “beyond the statutory scheme for impeaching him.” See G. L. c. 233, § 21 (imposing limits on when “[t]he conviction of a witness of a crime may be shown to affect his credibility . . .”).
We also reject the defendant’s related argument — not made at trial — that the judge should have allowed the admission of Roman’s and Dion’s convictions as “evidence to show that another person committed the crime or had the motive, intent and opportunity to commit it.”
Commonwealth
v.
Graziano,
Dion and Roman both testified that the defendant looked “nervous” just before the police arrived. Dion testified further that as the police arrived, the defendant “grabbed a broom, like he was working,” which Dion found “very suspicious.” Roman testified that the defendant had blood on his right hand and was covering his right hand with his left hand while the police were asking questions of the maintenance workers at the housing complex.
