Justice Scalia
delivered the opinion of the Court.
This case requires us to determine whether either the Confrontation Clause of the Sixth Amendment or Rule 802 of the Federal Rules of Evidence bars testimony concerning a prior, out-of-court identification when the identifying witness is unable, because of memory loss, to explain the basis for the identification.
I
On April 12, 1982, John Foster, a correctional counselor at the federal prison in Lompoc, California, was attacked and brutally beaten with a metal pipe. His skull was fractured, and he remained hospitalized for almost a month. As a result of his injuries, Foster’s memory was severely impaired. When Thomas Mansfield, an FBI agent investigating the assault, first attempted to interview Foster, on April 19, he found Foster lethargic and unable to remember his attacker’s name. On May 5, Mansfield again spoke to Foster, who was much improved and able to describe the attack. Foster named respondent as his attacker and identified respondent from an array of photographs.
Respondent was tried in Federal District Court for assault with intent to commit murder under 18 U. S. C. § 113(a). At trial, Foster recounted his activities just before the attack, and described feeling the blows to his head and seeing blood on the floor. He testified that he clearly remembered identifying respondent as his assailant during his May 5th interview with Mansfield. On cross-examination, he admitted that he could not remember seeing his assailant. He also admitted that, although there was evidence that he had received numerous visitors in the hospital, he was unable to remember any of them except Mansfield, and could not remember whether any of these visitors had suggested that respondent was the assailant. Defense counsel unsuccessfully sought to refresh his recollection with hospital records, including one indicating that Foster had attributed the assault to someone other than respondent. Respondent was convicted and sentenced to 20 years’ imprisonment to be served consecutively to a previous sentence.
On appeal, the United States Court of Appeals for the Ninth Circuit considered challenges based on the Confrontation Clause and Rule 802 of the Federal Rules of Evidence. By divided vote it upheld both challenges (though finding the Rule 802 violation harmless error), and reversed the judgment of the District Court. 789 F. 2d 750 (1986). We granted certiorari, 479 U. S. 1084 (1987), to resolve the conflict with other Circuits on the significance of a hearsay declarant’s memory loss both with respect to the Confrontation Clause, see, e. g., United States ex rel. Thomas v. Cuyler, 548 F. 2d 460, 462-463 (CA3 1977), and with respect to Rule 802, see, e. g., United States v. Lewis, 565 F. 2d 1248, 1252 (CA2 1977), cert. denied, 435 U. S. 973 (1978).
II
The Confrontation Clause of the Sixth Amendment gives the accused the right “to be confronted with the witnesses against him.” This has long been read as securing an adequate opportunity to cross-examine adverse witnesses. See, e. g., Mattox v. United States, 156 U. S. 237, 242-243 (1895); Douglas v. Alabama, 380 U. S. 415, 418 (1965). This Court has never held that a Confrontation Clause violation can be founded upon a witness’ loss of memory, but in two cases has expressly left that possibility open.
In California v. Green, 399 U. S. 149, 157-164 (1970), we found no constitutional violation in the admission of testimony that had been given at a preliminary hearing, relying on (as one of two independent grounds) the proposition that the opportunity to cross-examine the witness at trial satisfied the Sixth Amendment’s requirements. We declined, however, to decide the admissibility of the same witness’ out-of-court statement to a police officer concerning events that at trial he was unable to recall. In remanding on this point, we noted that the state court had not considered, and the parties had not briefed, the possibility that the witness’ memory loss so affected the petitioner’s right to cross-examine as to violate the Confrontation Clause. Id., at 168-169. Justice Harlan, in a scholarly concurrence, stated that he would have reached the issue of the out-of-court statement, and would have held that a witness’ inability to “recall either the underlying events that are the subject of an extra-judicial statement or previous testimony or recollect the circumstances under which the statement was given, does not have Sixth Amendment consequence.” Id., at 188.
In Delaware v. Fensterer, 474 U. S. 15 (1985) (per curiam), we determined that there was no Confrontation Clause violation when an expert witness testified as to what opinion he had formed, but could not recollect the basis on which he had formed it. We said:
“The Confrontation Clause includes no guarantee that every witness called by the prosecution will refrain from giving testimony that is marred by forgetfulness, confusion, or evasion. To the contrary, the Confrontation Clause is generally satisfied when the defense is given a full and fair opportunity to probe and expose these infirmities through cross-examination, thereby calling to the attention of the factfinder the reasons for giving scant weight to the witness’ testimony.” Id., at 21-22.
Our opinion noted that a defendant seeking to discredit a forgetful expert witness is not without ammunition, since the jury may be persuaded that “his opinion is as unreliable as his memory.” Id., at 19. We distinguished, however, the unresolved issue in Green on the basis that that involved the introduction of an out-of-court statement. 474 U. S., at 18. Justice Stevens, concurring in the judgment, suggested that the question at hand was in fact quite close to the question left open in Green. 474 U. S., at 23-24.
Here that question is squarely presented, and we agree with the answer suggested 18 years ago by Justice Harlan. “[T]he Confrontation Clause guarantees only ‘an opportunity for effective cross-examination, not cross-examination that is effective in whatever way, and to whatever extent, the defense might wish.’” Kentucky v. Stincer, 482 U. S. 730, 739 (1987), quoting Fensterer, supra, at 20 (emphasis added); Delaware v. Van Arsdall, 475 U. S. 673, 679 (1986); Ohio v. Roberts, 448 U. S. 56, 73, n. 12 (1980). As Fensterer demonstrates, that opportunity is not denied when a witness testifies as to his current belief but is unable to recollect the reason for that belief. It is sufficient that the defendant has the opportunity to bring out such matters as the witness’ bias, his lack of care and attentiveness, his poor eyesight, and even (what is often a prime objective of cross-examination, see 3A J. Wigmore, Evidence § 995, pp. 931-932 (J. Chadbourn rev. 1970)) the very fact that he has a bad memory. If the ability to inquire into these matters suffices to establish the constitutionally requisite opportunity for cross-examination when a witness testifies as to his current belief, the basis for which he cannot recall, we see no reason why it should not suffice when the witness’ past belief is introduced and he is unable to recollect the reason for that past belief. In both cases the foundation for the belief (current or past) cannot effectively be elicited, but other means of impugning the belief are available. Indeed, if there is any difference in persuasive impact between the statement “I believe this to be the man who assaulted me, but can’t remember why” and the statement “I don’t know whether this is the man who assaulted me, but I told the police I believed so earlier,” the former would seem, if anything, more damaging and hence give rise to a greater need for memory-testing, if that is to be considered essential to an opportunity for effective cross-examination. We conclude with respect to this latter example, as we did in Fensterer with respect to the former, that it is not. The weapons available to impugn the witness’ statement when memory loss is asserted will of course not always achieve success, but successful cross-examination is not the constitutional guarantee. They are, however, realistic weapons, as is demonstrated by defense counsel’s summation in this very case, which emphasized Foster’s memory loss and argued that his identification of respondent was the result of the suggestions of people who visited him in the hospital.
Our constitutional analysis is not altered by the fact that the testimony here involved an out-of-court identification that would traditionally be categorized as hearsay. See Advisory Committee’s Notes on Fed. Rule Evid. 801(d)(1)(C), 28 U. S. C. App., p. 717. This Court has recognized a partial (and somewhat indeterminate) overlap between the requirements of the traditional hearsay rule and the Confrontation Clause. See Green, 399 U. S., at 155-156; id., at 173 (Harlan, J., concurring). The dangers associated with hearsay inspired the Court of Appeals in the present case to believe that the Constitution required the testimony to be examined for “indicia of reliability,” Dutton v. Evans, 400 U. S. 74, 89 (1970), or “particularized guarantees of trustworthiness,” Roberts, supra, at 66. We do not think such an inquiry is called for when a hearsay declarant is present at trial and subject to unrestricted cross-examination. In that situation, as the Court recognized in Green, the traditional protections of the oath, cross-examination, and opportunity for the jury to observe the witness’ demeanor satisfy the constitutional requirements. 399 U. S., at 158-161. We do not think that a constitutional line drawn by the Confrontation Clause falls between a forgetful witness’ live testimony that he once believed this defendant to be the perpetrator of the crime, and the introduction of the witness’ earlier statement to that effect.
Respondent has argued that this Court’s jurisprudence concerning suggestive identification procedures shows the special dangers of identification testimony, and the special importance of cross-examination when such hearsay is proffered. See, e. g., Manson v. Brathwaite, 432 U. S. 98 (1977); Neil v. Biggers, 409 U. S. 188 (1972). Respondent has not, however, argued that the identification procedure used here was in any way suggestive. There does not appear in our opinions, and we decline to adopt today, the principle that, because of the mere possibility of suggestive procedures, out-of-court statements of identification are inherently less reliable than other out-of-court statements.
HH
Respondent urges as an alternative basis for affirmance a violation of Federal Rule of Evidence 802, which generally excludes hearsay. Rule 801(d)(1)(C) defines as not hearsay a prior statement “of identification of a person made after perceiving the person,” if the declarant “testifies at the trial or hearing and is subject to cross-examination concerning the statement.” The Court of Appeals found that Foster’s identification statement did not come within this exclusion because his memory loss prevented his being “subject to cross-examination concerning the statement.” Although the Court of Appeals concluded that the violation of the Rules of Evidence was harmless (applying for purposes of that determination a “more-probable-than-not” standard, rather than the “beyond-a-reasonable-doubt” standard applicable to the Confrontation Clause violation, see Delaware v. Van Arsdall, 475 U. S., at 684), respondent argues to the contrary.
It seems to us that the more natural reading of “subject to cross-examination concerning the statement” includes what was available here. Ordinarily a witness is regarded as “subject to cross-examination” when he is placed on the stand, under oath, and responds willingly to questions. Just as with the constitutional prohibition, limitations on the scope of examination by the trial court or assertions of privilege by the witness may undermine the process to such a degree that meaningful cross-examination within the intent of the Rule no longer exists. But that effect is not produced by the witness’ assertion of memory loss — which, as discussed earlier, is often the very result sought to be produced by cross-examination, and can be effective in destroying the force of the prior statement. Rule 801(d)(1)(C), which specifies that the cross-examination need only “concer[n] the statement,” does not on its face require more.
This reading seems even more compelling when the Rule is compared with Rule 804(a)(3), which defines “[unavailability as a witness” to include situations in which a declarant “testifies to a lack of memory of the subject matter of the declarant’s statement.” Congress plainly was aware of the recurrent evidentiary problem at issue here — witness forgetfulness of an underlying event — but chose not to make it an exception to Rule 801(d)(1)(C).
The reasons for that choice are apparent from the Advisory Committee’s Notes on Rule 801 and its legislative history. The premise for Rule 801(d)(1)(C) was that, given adequate safeguards against suggestiveness, out-of-court identifications were generally preferable to courtroom identifications. Advisory Committee’s Notes on Rule 801, 28 U. S. C. App., p. 717. Thus, despite the traditional view that such statements were hearsay, the Advisory Committee believed that their use was to be fostered rather than discouraged. Similarly, the House Report on the Rule noted that since, “[a]s time goes by, a witness’ memory will fade and his identification will become less reliable,” minimizing the barriers to admission of more contemporaneous identification is fairer to defendants and prevents “cases falling through because the witness can no longer recall the identity of the person he saw commit the crime.” H. R. Rep. No. 94-355, p. 3 (1975). See also S. Rep. No. 94-199, p. 2 (1975). To judge from the House and Senate Reports, Rule 801(d)(1)(C) was in part directed to the very problem here at issue: a memory loss that makes it impossible for the witness to provide an in-court identification or testify about details of the events underlying an earlier identification.
Respondent argues that this reading is impermissible because it creates an internal inconsistency in the Rules, since the forgetful witness who is deemed “subject to cross-examination” under 801(d)(1)(C) is simultaneously deemed “unavailable” under 804(a)(3). This is the position espoused by a prominent commentary on the Rules, see 4 J. Weinstein & M. Berger, Weinstein’s Evidence 801-120 to 801-121, 801-178 (1987). It seems to us, however, that this is not a substantive inconsistency, but only a semantic oddity resulting from the fact that Rule 804(a) has for convenience of reference in Rule 804(b) chosen to describe the circumstances necessary in order to admit certain categories of hearsay testimony under the rubric “Unavailability as a witness.” These circumstances include not only absence from the hearing, but also claims of privilege, refusals to obey a court’s order to testify, and inability to testify based on physical or mental illness or memory loss. Had the rubric instead been “unavailability as a witness, memory loss, and other special circumstances” there would be no apparent inconsistency with Rule 801, which is a definition section excluding certain statements entirely from the category of “hearsay.” The semantic inconsistency exists not only with respect to Rule 801(d)(1)(C), but also with respect to the other subparagraphs of Rule 801(d)(1). It would seem strange, for example, to assert that a witness can avoid introduction of testimony from a prior proceeding that is inconsistent with his trial testimony, see Rule 801(d)(1)(A), by simply asserting lack of memory of the facts to which the prior testimony related. See United States v. Murphy, 696 F. 2d 282, 283-284 (CA4 1982), cert. denied, 461 U. S. 945 (1983). But that situation, like this one, presents the verbal curiosity that the witness is “subject to cross-examination” under Rule 801 while at the same time “unavailable” under Rule 804(a)(3). Quite obviously, the two characterizations are made for two entirely different purposes and there is no requirement or expectation that they should coincide.
For the reasons stated, we hold that neither the Confrontation Clause nor Federal Rule of Evidence 802 is violated by admission of an identification statement of a witness who is unable, because of a memory loss, to testify concerning the basis for the identification. The decision of the Court of Appeals is reversed, and the case is remanded for proceedings consistent with this opinion.
So ordered.
Justice Kennedy took no part in the consideration or decision of this case.
This case has been argued, both here and below, as though Federal Rule of Evidence 801(d)(1)(C) were the basis of the challenge. That is substantially but not technically correct. If respondent’s arguments are accepted, it is Rule 802 that would render the out-of-court statement inadmissible as hearsay; but as explained in Part III, it is ultimately Rule 801(d)(1)(C) that determines whether Rule 802 is applicable.
On remand, the California Supreme Court concluded that the Confrontation Clause was not violated by the out-of-court statement, because the declarant testified under oath, subject to cross-examination, and the jury was able to observe his demeanor. People v. Green, 3 Cal. 3d 981, 479 P. 2d 998, cert. dism’d, 404 U. S. 801 (1971).