Justice White
announced the judgment of the Court and delivered an opinion, in which Justice Stewart, Justice Blackmun, and Justice Powell joined.
The question here is whether it was reversible error for a federal trial court in a criminal case to reject the defendant’s request that the court’s voir dire of prospective jurors inquire further into the possibility of racial or ethnic prejudice against the defendant.
I
Petitioner is of Mexican descent. In February 1979, he was tried before a jury in the United States District Court for the Southern District of California for his alleged participation in a plan by which three Mexican aliens were illegally brought into the country.
The Government’s evidence at trial described the following events. On the night of December 10, 1978, three aliens were led across the Mexican-American border and taken to a car, previously left for them on the American side. They drove to Imperial Beach, Cal., a town about eight miles inside the border. Early in the morning of December 11, they reached the home of Virginia Hendricks Bowling, where they were admitted into the garage of the house by petitioner. Bowling was an American citizen, apparently Caucasian, living in Imperial Beach with her 19-year-old daughter. Petitioner had been living with Bowling’s daughter in her mother’s house since July 1978.
Later in the morning, petitioner hid the three aliens and their guide in the trunk of a green Oldsmobile. Bowling drove the Oldsmobile north, through the San Clemente checkpoint, while petitioner followed in a grey Ford. After passing through the checkpoint, Bowling and petitioner exchanged cars. Petitioner proceeded to Los Angeles in the Oldsmobile and Bowling returned to Imperial Beach in the Ford. In Los Angeles, petitioner went to an apartment, which agents of the Immigration and Naturalization Service had had under surveillance for several weeks because they suspected that it was a drop site for illegal aliens. Upon arrival, the aliens were let out of the trunk and told to go into the apartment by petitioner. Shortly thereafter, petitioner was arrested when he left the apartment with one of the aliens.
At trial, the INS agents, Bowling, the three illegal aliens, and David Falcon-Zavala, another named principal in the smuggling arrangement who was arrested with petitioner, testified for the Government. Petitioner did not testify; his defense was principally to challenge the credibility of the Government witnesses. The jury convicted him of all the charges and the Court of Appeals for the Ninth Circuit affirmed. 617 F. 2d 1349 (1980).
Prior to trial, petitioner’s counsel formally requested that he be allowed personally to voir dire the prospective members of the jury. At the same time, he filed a list of 26 questions that he requested the trial judge to ask, if the court denied his first motion. Among the questions submitted was one directed toward possible prejudice toward Mexicans:
“Would you consider the race or Mexican descent of Humberto Rosales-Lopez in your evaluation of this case? How would it affect you?”
As permitted by Rule 24 of the Federal Rules of Criminal Procedure and pursuant to the practice in the Southern District of California, the trial judge conducted the voir dire himself. He asked about half of the questions submitted by petitioner. Although he did not ask any question directed specifically to possible racial or ethnic prejudice, he did ask a question directed to attitudes toward the substantive charges involved: “Do any of you have any feelings about the alien problem at all?” He subsequently rephrased this: “Do any of you have any particular feelings one way or the other about aliens or could you sit as a fair and impartial juror if you are called upon to do so?” App. 17-18. The judge began the voir dire with the following general statement to the panel:
“In order that this defendant shall have a fair and impartial jury to try the charges against him, it is necessary that we address certain questions to the panel to make sure that there are no underlying prejudices, there are no underlying reasons why you can’t sit as a fair and impartial juror if chosen to do so in this case.” Id., at 14.
He ended his general questioning with the following:
“Does any reason occur to anyone'of you why you could not sit in this case as a fair and impartial juror, any reason whatsoever?” Id., at 21.
Following the voir dire, defense counsel restated his request with respect to six of the submitted questions, including the one directed toward racial or ethnic prejudice. He argued at sidebar that under Aldridge v. United States, 283 U. S. 308 (1931), a federal court “must explore all racial antagonism against my client because he happens to be of Mexican descent.” App. 25. The judge declined to ask any further questions of the jury panel. Peremptory challenges were then exercised and the jury was sworn.
Petitioner appealed, unsuccessfully challenging the refusal of the trial judge to question the jurors about possible racial or ethnic bias. The Court of Appeals for the Ninth Circuit noted that there is
“[a] longstanding rule of criminal justice in the federal courts . . . that questions regarding possible racial prejudice should be put to the venire in prosecutions of minority defendants, at least where ‘special circumstances’ indicate that the defendant’s race may be a factor in the trial.” 617 F. 2d, at 1354.
The court noted that “[t]he extent of the federal rule is unclear.” Ibid. It concluded, however, that this case did not contain such “special circumstances.”
The Courts of Appeals have adopted conflicting rules as to when the failure to ask such questions will constitute reversible error. Some Circuits have adopted a per se rule, requiring reversal whenever the trial judge fails to ask a question on racial or ethnic prejudice requested by a defendant who is a member of a minority group. See United States v. Bowles, 574 P. 2d 970 (CA8 1978); United States v. Robinson, 485 P. 2d 1157 (CA3 1973); United States v. Carter, 440 P. 2d 1132 (CA6 1971); United States v. Gore, 435 P. 2d 1110 (CA4 1970); Frasier v. United States, 267 F. 2d 62 (CA1 1959). Other Circuits, including the Ninth, have rejected such a per se rule, holding that a trial judge is required to pose such a question only where there is some indication that the particular case is likely to have racial overtones or involve racial prejudice. See United States v. Polk, 550 F. 2d 1265 (CA10 1977); United States v. Perez-Martinez, 525 F. 2d 365 (CA9 1975). In light of this diversity of views, we granted certiorari. 449 U. S. 819.
II
Voir dire plays a critical function in assuring the criminal defendant that his Sixth Amendment right to an impartial jury will be honored. Without an adequate voir dire the trial judge’s responsibility to remove prospective jurors who will not be able impartially to follow the court’s instructions and evaluate the evidence cannot be fulfilled. See Connors v. United States, 158 U. S. 408, 413 (1895). Similarly, lack of adequate voir dire impairs the defendant’s right to exercise peremptory challenges where provided by statute or rule, as it is in the federal courts.
Despite its importance, the adequacy of voir dire is not easily subject to appellate review. The trial judge’s function at this point in the trial is not unlike that of the jurors later on in the trial. Both must' reach conclusions as to impartiality and credibility by relying on their own evaluations of demeanor evidence and of responses to questions. See Ristaino v. Ross, 424 U. S. 589, 595 (1976), quoting Rideau v. Louisiana, 373 U. S. 723, 733 (1963) (Clark, J., dissenting). In neither instance can an appellate court easily second-guess the conclusions of the decisionmaker who heard and observed the witnesses.
Because the obligation to impanel an impartial jury lies in the first instance with the trial judge, and because he must rely largely on his immediate perceptions, federal judges have been accorded ample discretion in determining how best to conduct the voir dire. In Aldridge v. United States, 283 U. S. 308 (1931), the Court recognized the broad role of the trial court: “[T]he questions to the prospective jurors were put by the court, and the court had a broad discretion as to the questions to be asked.” Id., at 310. See also Ham v. South Carolina, 409 U. S. 524, 528 (1973) (recognizing “the traditionally broad discretion accorded to the trial judge in conducting voir dire . . .”). Furthermore, Rule 24 (a), Federal Rules of Criminal Procedure, provides that the trial court may decide to conduct the voir dire itself or may allow the parties to conduct it. If the court conducts it, the parties may “supplement the examination by such further inquiry as [the court] deems proper”; alternatively, the court may limit participation to the submission of additional questions, which the court must ask only “as it deems proper.”
There are, however, constitutional requirements with respect to questioning prospective jurors about racial or ethnic bias. The “special circumstances” under which the Constitution requires a question on racial prejudice were described in Ristaino v. Ross, supra, by contrasting the facts of that case with those in Ham v. South Carolina, supra, in which we held it reversible error for a state court to fail to ask such a question.
Ham involved a black defendant charged with a drug offense. His defense was that the law enforcement officers had “framed” him in retaliation for his active, and widely known, participation in civil rights activities. The critical factor present in Ham, but not present in Ristaino, was that racial issues were “inextricably bound up with the conduct of the trial,” and the consequent need, under all the circumstances, specifically to inquire into possible racial prejudice in order to assure an impartial jury. Ristaino, supra, at 596, 597. Although Ristaino involved an alleged criminal confrontation between a black assailant and a white victim, that fact pattern alone did not create a need of “constitutional dimensions” to question the jury concerning racial prejudice. 424 U. S., at 596, 597. There is no constitutional presumption of juror bias for or against members of any particular racial or ethnic groups. As Ristaino demonstrates, there is no per se constitutional rule in such circumstances requiring inquiry as to racial prejudice. Id., at 596, n. 8. Only when there are more substantial indications of the likelihood of racial or ethnic prejudice affecting the jurors in a particular case does the trial court’s denial of a defendant’s request to examine the jurors’ ability to deal impartially with this subject amount to an unconstitutional abuse of discretion.
Absent such circumstances, the Constitution leaves it to the trial court, and the judicial system within which that court operates, to determine the need for such questions. In the federal court system, we have indicated that under our supervisory authority over the federal courts, we would require that questions directed to the discovery of racial prejudice be asked in certain circumstances in which such an inquiry is not constitutionally mandated. Ristaino, supra, at 597, n. 9.
Determination of an appropriate nonconstitutional standard for the federal courts does not depend upon a comparison of the concrete costs and benefits that its application is likely to entail. These are likely to be slight: some delay in the trial versus the occasional discovery of an unqualified juror who would not otherwise be discovered. There is, however, a more significant conflict at issue here — one involving the appearance of justice in the federal courts. On the one hand, requiring an inquiry in every case is likely to create the impression “that justice in a court of law may turn upon the pigmentation of skin [or] the accident of birth.” Ristaino, supra, at 596, n. 8. Trial judges are understandably hesitant to introduce such a suggestion into their courtrooms. See Aldridge, supra, at 310; Ristaino, supra, at 591. Balanced against this, however, is the criminal defendant’s perception that avoiding the inquiry does not eliminate the problem, and that his trial is not the place in which to elevate appearance over reality.
We first confronted this conflict in Aldridge, supra, and what we said there remains true today:
“The argument is advanced on behalf of the Government that it would be detrimental to the administration of the law in the courts of the United States to allow questions to jurors as to racial or religious prejudices. We think that it would be far more injurious to permit it to be thought that persons entertaining a disqualifying prejudice were allowed to serve as jurors and that inquiries designed to elicit the fact of disqualification were barred. No surer way could be devised to bring the processes of justice into disrepute.” 283 U. S., at 314^315.
In our judgment, it is usually best to allow the defendant to resolve this conflict by making the determination of whether or not he would prefer to have the inquiry into racial or ethnic prejudice pursued. Failure to honor his request, however, will be reversible error only where the circumstances of the case indicate that there is a reasonable possibility that racial or ethnic prejudice might have influenced the jury.
In Ristaino, the Court indicated that under the circumstances of that case, a federal trial court would have been required to “propound appropriate questions designed to identify racial prejudice if requested by the defendant.” 424 U. S., at 597, n. 9. In Ristaino, the Court also made clear that the result reached in Aldridge, was based on this Court’s supervisory power over the federal courts. 424 U. S., at 598, n. 10. In Aldridge, which Ristaino embraced, the Court held that it was reversible error for a federal trial court to fail to inquire into racial prejudice in a case involving a black defendant accused of murdering a white policeman. The circumstances of both cases indicated that there was a “reasonable possibility” that racial prejudice would influence the jury.
Aldridge and Ristaino together, fairly imply that federal trial courts must make such an inquiry when requested by a defendant accused of a violent crime and where the defendant and the victim are members of different racial or ethnic groups. This supervisory rule is based upon and consistent with the “reasonable possibility standard” articulated above. It remains an unfortunate fact in our society that violent crimes perpetrated against members of other racial or ethnic groups often raise such a possibility. There may be other circumstances that suggest the need for such an inquiry, but the decision as to whether the total circumstances suggest a reasonable possibility that racial or ethnic prejudice will affect the jury remains primarily with the trial court, subject to case-by-case review by the appellate courts.
Ill
Evaluated against these standards, there was no reversible error in the voir dire afforded petitioner. At no point has petitioner argued that the matters at issue in his trial involved allegations of racial or ethnic prejudice: neither the Government’s case nor his defense involved any such allegations. There were, then, no “special circumstances” of constitutional dimension in this case. Neither did the circumstances of the case reveal a violent criminal act with a victim of a different racial or ethnic group. In fact, petitioner was accused of a victimless crime: aiding members of his own ethnic group to gain illegal entry into the United States. Petitioner, therefore, falls within that category of cases in which the trial court must determine if the external circumstances of the case indicate a reasonable possibility that racial or ethnic prejudice will influence the jury’s evaluation of the evidence. For two reasons, we do not believe that such a reasonable possibility has been demonstrated in this case.
First, the trial court reasonably determined that a juror’s prejudice toward aliens might affect his or her ability to serve impartially in this case. The court, therefore, questioned the prospective jurors as to their attitudes toward aliens. There can be no doubt that the jurors would have understood a question about aliens to at least include Mexican aliens. The trial court excused two jurors for cause, based on their responses to this question. Removing these jurors eliminated, we believe, any reasonable possibility that the remaining jurors would be influenced by an undisclosed racial prejudice toward Mexicans that would have been disclosed by further questioning.
Second, petitioner contends that “any latent racial antagonism” of the jurors toward Mexicans was likely to be exacerbated by Bowling’s testimony concerning the relationship between petitioner and her daughter. Petitioner, however, failed to make this argument to the trial court in support of his requested question. Even if he had, however, it would not create a reasonable possibility that the jury’s determination would be influenced by racial prejudice. Bowling’s testimony as to petitioner’s role in the particular smuggling operation involved in this trial was substantially corroborated by the other witnesses presented by the Government, including Falcon-Zavala and the three illegal aliens. Under the circumstances of this case, the racial or ethnic differences between the defendant and a key Government witnesss did not create a situation meeting the standard set out above. The judge was not, therefore, required to inquire further than he did.
Under these circumstances, we cannot hold that there was a reasonable possibility that racial or ethnic prejudice would affect the jury. Therefore, the trial court did not abuse its discretion in denying petitioner’s request, and the judgment of the Court of Appeals is affirmed.
So ordered.
Petitioner was charged with one count of conspiracy to conceal, harbor and shield, and illegally transport aliens, in violation of 18 U. S. C. § 371 and 8 U. S. C. § 1324; three counts of aiding and abetting the illegal transportation of aliens, in violation of 8 U. S. C. § 1324 (a) (2) and 18 U. S. C. §2, and three counts of concealing, harboring, and shielding aliens, in violation of 8 U. S. C. § 1324 (a) (3).
The trial court asked the panel as a group questions concerning the following: knowledge of the participants in the trial; outside knowledge of the case; physical impairments that would interfere with their responsibilities as jurors; legal training; possible disagreement with the principle that a criminal defendant is presumed to be innocent. Each juror was asked to state some basic facts about himself or herself, including name, occupation, and spouse’s occupation.
Two jurors were excused because of their responses to this question.
The other five questions were:
1. “Have you ever employed or have friends that have employed illegal aliens?”
2. “Have you ever worked for the federal Government? If so, as what? How long?”
3. “Have you ever been the victim of a crime?”
4. “Have you ever sat as a juror in a civil or criminal case? What was the nature of the case and the verdict?”
5. “Are you able to speak Spanish? If so, how well? Would you be willing to accept the interpreter’s translation?”
On appeal, petitioner also challenged the failure of the trial court to provide him a free copy of the transcript of a suppression hearing, the sentencing procedure applied to him, the denial of an evidentiary hearing on possible prosecutorial vindictiveness, the trial court’s refusal to give an instruction on a lesser-included offense, the propriety of imposing consecutive sentences, and the constitutionality of 8 U. S. C. § 1324. ’ The Court of Appeals rejected all of these contentions.
In Swain v. Alabama, 380 U. S. 202 (1965), we noted the connection between voir dire and the exercise of peremptory challenges: “The voir dire in American trials tends to be extensive and probing, operating as a predicate for the exercise of peremptories . . . .” Id., at 218-219. We also noted there that although there is no federal constitutional requirement that peremptory challenges be permitted, the challenge is widely used in federal and state courts pursuant to statute or rule and is deemed to be an important aspect of trial by jury. Id., at 219.
Of course, the judge need not defer to a defendant’s request where there is no rational possibility of racial prejudice. But since the courts are seeking to assure the appearance and reality of a fair trial, if the defendant claims a meaningful ethnic difference between himself and the victim, his voir dire request should ordinarily be satisfied.
We also note that the trial court asked generally whether there were any grounds which might occur to the jurors as to why they could not sit as “fair and impartial” jurors. Coupled with the question concerning aliens, there is little reason to believe that a juror who did not answer this general question would have answered affirmatively a question directed narrowly at racial prejudice.