The defendant is here on an amended bill of exceptions after conviction under an indictment charging robbery. He was also tried and found not guilty under indictments charging him with the commission of an unnatural and lascivious act and assault and battery. We overrule the exceptions.

In this case, we are required once again to consider the scope and applicability of the United States Supreme Court’s holding in Ham v. South Carolina, 409 U. S. 524 (1973). In Commonwealth v. Ross, 363 Mass. 665 (1973), cert. den. 414 U. S. 1080 (1973), we said that “ [w]e do not believe that the Ham case announced a new broad constitutional principle requiring that questions, designed to discover possible racial prejudice, be put to prospective jurors in all State criminal trials when the defendant is black.” Id. at 671. We went on to say that such questions are constitutionally mandated only when the defendant was a “special target for racial prejudice,” (id. at 672) as the defendant in the Ham case had been. Our holding in the Ross case has been followed consistently by this court. See Commonwealth v. Ryles, 363 Mass. 674, 676 (1973), cert. den. 414 U. S. 980 (1973); Commonwealth v. Rodriquez, 364 Mass. 87, 92-93 (1973); Commonwealth v. Bumpus, 365[*215] Mass. 66, 67 (1974); Commonwealth v. Pinckney, 365 Mass. 70, 73 (1974). Today we reaffirm that holding.

The circumstances in the Ham case were novel. The defendant, a young black man, was well known as a civil rights activist in the small community where he had resided for most of his life. At the time of his trial, he had no prior record of convictions. His principal defense was that the local law enforcement authorities were “out to get him” because of his civil rights activities and had “framed” him on the charge of marihuana possession. With this factual background, the United States Supreme Court reversed his conviction. The court held that the trial judge in the voir dire improperly failed to examine potential jurors on the issue of racial bias. Mr. Justice Rehnquist, writing for the court, carefully limited the holding to the facts in the case: “The State having created this statutory framework for the selection of juries, the essential fairness required by the Due Process Clause of the Fourteenth Amendment requires that under the facts shown by this record the petitioner be permitted to have the jurors interrogated on the issue of racial bias” (emphasis supplied). Ham v. South Carolina, 409 U. S. 524, 527 (1973).

Racial issues infected the entire Ham trial. The issues were inescapably and powerfully before the jurors. Bias formed the heart of the defense. The defendant rightfully contended that bias, official and covert, was the sole cause and foundation for the prosecution. The defendant fought bias in his civil rights activities, undoubtedly known to jurors drawn from the locality. Any latent bias harbored by the jurors would likely have been activated by the case and would have defeated the defendant’s efforts to achieve acquittal. When the racial issues were so salient and Ham, himself, was a special target for prejudice, the due process clause plainly entitled Ham to have the judge examine jurors for racial prejudice.

[*216] Yet, in the light of the language of Mr. Justice Rehnquist quoted above, we do not believe that the due process clause mandates such examination in every case in which there is a black defendant. ^[1] We adhere to our prior holdings, cited above, that the defendant must be a special target for prejudice before the constitutional guaranties are invoked.

In the ordinary case, inquiries beyond the statutory questions, which raise generally the issue of bias, rest in the sound discretion of the trial judge. Commonwealth v. Nassar, 354 Mass. 249, 253 (1968). Absent the above mentioned factors which make the defendant a special target for racial prejudice, there is no constitutional compulsion to ask questions beyond the statutory questions. “ [T]he statutory questions . . . [are] sufficient to insure the ‘essential demands of fairness’ required by the Fourteenth Amendment.” Commonwealth v. Ryles, 363 Mass. 674, 676-677 (1973), cert. den. 414 U. S. 980 (1973). However, as a practical matter, when a motion that prospective jurors be interrogated as to possible prejudice is presented, we believe the trial judge should grant that motion. ^[2] Such a motion, raising as it does difficult issues of jury psychology and potential injury to[*217] the defendant’s case, should come from the defendant himself. Before granting the motion, the trial judge should carefully ascertain that the defendant’s decision to insist on specific questions regarding racial bias was a knowing and voluntary one, made with an understanding that such specific questions may activate latent racial bias in certain prospective jurors or may insult others without uncovering evidence of bias in hard-core bigots who refuse to acknowledge their prejudice. ^[3] If, thereafter, the defendant insists that specific questions concerning bias be asked, the judge should propound such questions to the veniremen. The decision then has been the defendant’s to make. Granting the request for special interrogation may avoid needless appeals which lack constitutional substance under our interpretation of the Ham case. ^[4]

This court’s interpretation of the Ham case was before the United States Court of Appeals for the First Circuit[*218] recently in Ross v. Ristaino, 508 F. 2d 754 (1st Cir. 1974), an application for a writ of habeas corpus filed by the defendant in Commonwealth v. Ross. The Court of Appeals, by a divided court, did not attempt to “resolve . . . [the] ambiguity” it found in the Ham opinion and, for purposes of argument, accepted the requirement that the defendant be a special target for prejudice. Id. at 756. The court, with Judge Moore dissenting, then approved an implicit finding of the Federal District Court that “a black defendant charged with violent crimes against a white security officer would be likely to be a special target of racial prejudice.” Ibid.

“[Although we give respectful consideration to such lower Federal court decisions as seem persuasive,” we are, of course, “not concluded by decisions of . . . [lower] Federal courts.” Commonwealth v. Masskow, 362 Mass. 662, 667 (1972). We cannot agree that the mere accusation of a black defendant in a crime with a white victim or the fact that the victim is a security guard constitutes “circumstances which reasonably present the issue of racial prejudice” (Commonwealth v. Ryles, 363 Mass. 674, 676 [1973], cert. den. 414 U. S. 980 [1973]), and make the defendant a special target for racial prejudice. See Commonwealth v. Ross, 363 Mass. 665, 672 (1973), cert. den. 414 U. S. 1080 (1973); Commonwealth v. Bumpus, 365 Mass. 66 (1974). “We have several times indicated that the fact that the defendant is black and the victim white does not suffice to bring a case within the Ham rule and to require specific questions by the trial judge as to possible prejudice among the veniremen.” Commonwealth v. Bumpus, supra, at 67. The ethnic identities of the defendant and victim, without other factors underscoring the racial elements of the case and their specific application to the defendant, are insufficient to invoke the special precautions of the Ham case. The victim’s occupation alone is not one such factor.

[*219] It is appropriate at this point to note that the expansive construction of the Ham holding adopted by the United States Court of Appeals for the First Circuit would have a calamitous impact on the criminal justice systems of many States if the construction were accepted as good constitutional law and applied retroactively ^[5] to all prior trials. Reliance on former constitutional standards, which left the specific content of voir dire questions in State courts to the trial judge, for many years was widespread in this and other jurisdictions. See, e.g., Commonwealth v. Ross, 361 Mass. 665 (1972), judgment vacated 410 U. S. 901 (1973), affd. on rehearing 363 Mass. 665 (1973), cert. den. 414 U. S. 1080 (1973); State v. Ham, 256 S. C. 1 (1971), revd. 409 U. S. 524 (1973). The prior case law and Supreme Court decisions gave no forewarning that certain specific questions concerning racial bias might be obligatory as a matter of Fourteenth Amendment due process. If the First Circuit’s construction of the Ham case were given retroactive, general application, many of those convicted and incarcerated after otherwise fair trials, which had resulted in deserved convictions, would be able to come before State and[*220] Federal courts seeking relief from those convictions. While we lack precise statistics as to the number of convicted defendants potentially affected (cf. Tehan v. United States ex rel. Shott, 382 U. S. 406, 418 [1966]), our experience suggests that the number is significant. Prior to any amplifying construction of the Ham case or any ruling of retroactivity, seven convicted defendants ^[6] have asked us to reverse their convictions because, they contended, failure to interrogate jurors specifically about racial prejudice abridged their rights under the due process clause. Without doubt, many more will surface if the First Circuit’s construction of the Ham case is accepted and given retroactive effect. Each claimant would be entitled to a hearing on the issue whether he had requested that a question as to racial bias be put to potential jurors. Each claimant who had been successful in that initial stage of the hearing would then attempt to prove that the circumstances of his case fit within the enlarged Ham rule. The hearings and consequent appeals alone ^[7] would severely exacerbate the intolerable congestion of our already congested criminal sessions. The plethora of proceedings would disrupt the orderly administration of criminal justice and preclude consideration of other cases in our criminal courts. These practical considerations buttress our belief that, as a matter of constitutional principle, the Ham holding is properly restricted quite narrowly to the special circumstances presented by that case and similar cases.

With this view of the law in mind, we turn now to the evidence in the instant case, before us on the defendant’s[*221] amended bill of exceptions. The Commonwealth’s evidence tended to show the following. On February 19, 1972, the victim, a white woman, working as a cocktail waitress, canvassed the Prudential Center area of Boston in search of new employment. Unsuccessful in her search, she was walking along Boylston Street when she was accosted by the defendant. He asked her why she looked so depressed. On being told of her failure to find a new job, he offered to help and suggested that they repair to his apartment to discuss the matter. The victim at first refused, but then acquiesced.

There was further evidence that at the defendant’s apartment the two engaged in general conversation for some time. As the conversation progressed, the victim became increasingly uneasy. When she stood up to leave, the defendant began to caress her body. She protested, but was ultimately forced to disrobe and engage in unnatural acts with the defendant.

The victim remained in the defendant’s apartment overnight. At one point, she attempted to escape ^[8] and was apprehended by the defendant. He then barricaded the door with a chest. Later, the victim was again forced to engage in sexual acts with the defendant.

The following morning the victim was permitted to leave. However, before her departure the defendant searched her belongings and removed $47. This money was recovered by the police when they arrested the defendant shortly after the victim’s release.

At trial, the defendant was convicted of robbery, but was acquitted of assault and battery and commission of an unnatural and lascivious act. Notwithstanding his acquittal on the charges involving sex and violence, the defendant argues ^[9] forcefully that the sexual overtones of the case present a special circumstance which entitled[*222] him to have questions concerning racial bias ^[10] put to the venire in the voir dire. We cannot agree that the refusal of the judge so to interrogate the prospective jurors required reversal in this case.

We cannot say that the facts of this case made the defendant more a special target for racial prejudice than any other black defendant who allegedly committed a crime of violence against a white victim. This case does not present the racial issues more vividly than a case involving a “brutal and unprovoked attack” on a white security guard who “received serious, multiple stab wounds” (Commonwealth v. Ross, 361 Mass. 665, 668 [1972], judgment vacated 410 U. S. 901 [1973], affd. on rehearing 363 Mass. [1973], cert. den. 414 U. S. 1080 [1973] ), or a murder of a white bank officer in the course of a bank robbery (Commonwealth v. Bumpus, 365 Mass. 66 [1974]). The defendant did not allege any racial motivation on the part of arresting officers or specify any circumstances beyond the facts of the crime which would have led the jurors to think particularly of the racial context. There was no allegation or proof, as there had been in the Ham case, that the defendant’s[*223] arrest and prosecution had been undertaken in reaction to civil rights organizing or racially provocative activities. We note here that the jury acquitted the defendant of the sexual charges which, he alleged, were highly inflammatory and potentially prejudicial. Though obviously the acquittal cannot establish the constitutional sufficiency of the voir dire interrogation, it is strong evidence that the jurors were, in fact, impartial and that the voir dire conducted by the trial judge was appropriate in these circumstances. Would the result have been the same if the judge had underscored the racial issue by putting pointed questions to the potential jurors? “[A trial] judge might well conclude that specific questions would be counter-productive and serve to inject racial bias into the trial rather than to remove it.” Commonwealth v. Bumpus, 365 Mass. 66, 67 (1974).

There is no merit in the defendant’s further contention that the Ham case is applicable here on the ground that the key issue in the instant case was the victim’s credibility. It is true that in Commonwealth v. Ross, 363 Mass. 665 (1973), cert. den. 414 U. S. 1080 (1973), we said: “The posture of the [Ham] case thus placed great emphasis on the issue of the credibility of the defendant in light of his reputation as opposed to that of the credibility of the police.” Id. at 666. However, a conflict of testimony alone is insufficient to bring a case within the doctrine of the Ham case. In Commonwealth v. Pinckney, 365 Mass. 70 (1974), we held that the fact that “the defendant took the stand and that his credibility as opposed to that of white witnesses was the crux of the case is not enough to create special circumstances requiring that specific questions on racial prejudice be put to the venire.” Id. at 73. In addition, even if a conflict of testimony by the black defendant and white witnesses would be sufficient to “requir[e] that specific questions on racial prejudice be put to the venire” (ibid.), no such conflict arose in the instant case. The defendant did not .take the stand to testify. Commonwealth v.[*224] Ryles, 363 Mass. 674, 676 (1973), cert. den. 414 U. S. 980 (1973). The jurors had to decide only whether they credited the testimony of the victim in the light of the other evidence.

The denial of the defendant’s motion to put the special questions to the prospective jurors was not a denial of due process under the Fourteenth Amendment.

Exceptions overruled.