During respondent's murder trial in a Delaware court, the State
sought to prove that a cat leash was the weapon used in strangling
the victim, and that a hair found on the leash was similar to the
victim's hair, and had been forcibly removed. The State's expert
witness testified that, in his opinion, the hair had been forcibly
removed, but stated, on both direct examination and
cross-examination, that he could not recall which of three methods
he had employed in determining that the hair had been forcibly
removed. The trial court overruled respondent's objection that the
admission of the expert's testimony precluded adequate
cross-examination unless he could testify as to which of the
methods he relied upon. The defense offered its own expert, who
testified that he had talked earlier with the State's expert and
had been informed as to the method employed by the State's expert
in reaching his "forcible removal" conclusion. The defense's expert
then proceeded to challenge the premise of that method. Respondent
was convicted, but the Delaware Supreme Court reversed, holding
that, because the State's expert was unable to recall the method he
used in arriving at his opinion, the admission of the opinion
violated respondent's rights under the Confrontation Clause of the
1. The admission of the State's expert's opinion did not offend
the Confrontation Clause, despite his inability to recall the basis
for that opinion. This case does not fall within the category of
Confrontation Clause cases involving the admission of out-of-court
statements as substantive hearsay evidence against the defendant
and his literal right to "confront" the witness at the time of
trial. The State made no attempt to introduce an out-of-court
statement by its expert for any purpose, let alone as hearsay. Nor
does this case fall within the category of Confrontation Clause
cases involving restrictions imposed by law or by the trial court
on the scope of cross-examination of prosecution witnesses. The
trial court here did not limit the scope or nature of defense
counsel's cross-examination of the State's expert. Generally
speaking, the Confrontation Clause guarantees an
for effective cross-examination (as in this
case), not cross-examination that is effective in whatever way, and
to whatever extent, the defense might wish.
Page 474 U. S. 16
2. The prosecution's foreknowledge that its expert would be
unable to give the precise basis for his opinion did not impose an
obligation on it, as a matter of due process, to refrain from
introducing the expert's testimony unless the basis for that
testimony could definitely be ascertained. Whether or not, under
state law, the State's expert's opinion should have been admitted,
the Federal Constitution does not forbid the trial court's
conclusion that the expert's inability to recall the basis for his
opinion went to the weight of the evidence, not its admissibility.
The testimony of the defense's expert, suggesting the actual basis
for the State's expert's opinion and disputing its validity,
dispels any possibility of a claim that the introduction of the
State's expert's opinion was so lacking in reliability and so
prejudicial as to deny respondent a fair trial.
Certiorari granted; 493
, reversed and remanded.
In this case, the Delaware Supreme Court reversed respondent
William Fensterer's conviction on the grounds that the admission of
the opinion testimony of the prosecution's expert witness, who was
unable to recall the basis for his opinion, denied respondent his
Sixth Amendment right to confront the witnesses against him.
(1985). We conclude that the Delaware Supreme Court
misconstrued the Confrontation Clause as interpreted by the
decisions of this Court.
Respondent was convicted of murdering his fiancée, Stephanie Ann
Swift. The State's case was based on circumstantial evidence, and
proceeded on the theory that respondent had strangled Swift with a
cat leash. To establish that the cat leash was the murder weapon,
the State sought to prove that two hairs found on the leash were
similar to Swift's hair, and that one of those hairs had been
forcibly removed. To prove these theories, the State relied on the
testimony of Special Agent Allen Robillard of the Federal Bureau of
At trial, Robillard testified that one of the hairs had been
forcibly removed. He explained that, in his opinion, there are
three methods of determining that a hair has forcibly
Page 474 U. S. 17
been removed: (1) if the follicular tag is present on the hair,
(2) if the root is elongated and misshaped, or (3) if a sheath of
skin surrounds the root. However, Robillard went on to say that
"I have reviewed my notes, and I have no specific knowledge as
to the particular way that I determined the hair was forcibly
removed other than the fact that one of those hairs was forcibly
at 963. On cross-examination, Agent Robillard was
again unable to recall which method he had employed to determine
that the hair had forcibly been removed. He also explained that
what he meant by "forcibly removed" was no more than that the hair
could have been removed by as little force as is entailed in
"brushing your hand through your head or brushing your hair.'"
Pet. for Cert. 7. The trial court overruled respondent's objection
that the admission of Robillard's testimony precluded adequate
cross-examination unless he could testify as to which of the three
theories he relied upon, explaining that, in its view, this
objection went to the weight of the evidence, rather than its
The defense offered its own expert in hair analysis, Dr. Peter
DeForest, who agreed with Agent Robillard that the hairs were
similar to Swift's. Doctor DeForest testified that he had observed
that one of the hairs had a follicular tag. He also testified that
he had spoken by telephone with Robillard, who advised him that his
conclusion of forcible removal was based on the presence of the
follicular tag. App. to Pet. for Cert. D-2. Doctor DeForest then
proceeded to challenge the premise of Robillard's theory -- that
the presence of a follicular tag indicates forcible removal.
According to Dr. DeForest, no adequate scientific study supported
that premise, and a follicular tag could be attached to hairs that
naturally fall out.
On appeal, the Delaware Supreme Court reversed respondent's
conviction on the authority of the Confrontation Clause. Noting
that "[t]he primary interest secured by the Clause is the right of
cross-examination," 493 A.2d at 963,
Page 474 U. S. 18
the court reasoned that
"[e]ffective cross-examination and discrediting of Agent
Robillard's opinion at a minimum required that he commit himself to
the basis of his opinion."
at 964 (footnote omitted). Absent such an
acknowledgment of the basis of his opinion, the court believed that
"defense counsel's cross-examination of the Agent was nothing more
than an exercise in futility." Ibid.
Since the court could
not rule out the possibility that Robillard could have been
"completely discredited" had he committed himself as to the theory
on which his conclusion was based, it held that respondent "was
denied his right to effectively cross-examine a key state witness."
Accordingly, the court reversed without reaching
respondent's additional claim that Robillard's testimony was
inadmissible under the pertinent Delaware Rules of Evidence. We now
reverse the Delaware Supreme Court's holding that Agent Robillard's
inability to recall the method whereby he arrived at his opinion
rendered the admission of that opinion violative of respondent's
rights under the Confrontation Clause.
This Court's Confrontation Clause cases fall into two broad
categories: cases involving the admission of out-of-court
statements and cases involving restrictions imposed by law or by
the trial court on the scope of cross-examination. The first
category reflects the Court's longstanding recognition that the
"literal right to confront' the witness at the time of trial .
. . forms the core of the values furthered by the Confrontation
Clause." California v. Green, 399 U.
S. 149, 399 U. S. 157
(1970). Cases such as Ohio v. Roberts, 448 U. S.
56 (1980), and Dutton v. Evans, 400 U. S.
74 (1970), gave rise to Confrontation Clause issues
"because hearsay evidence was admitted as substantive evidence
against the defendants." Tennessee v. Street, 471 U.
S. 409, 471 U. S. 413
(1985). Cf. Bruton v. United States, 391 U.
S. 123 (1968).
Page 474 U. S. 19
The second category of cases is exemplified by Davis v.
Alaska, 415 U. S. 308
415 U. S. 318
(1974), in which, although some cross-examination of a prosecution
witness was allowed, the trial court did not permit defense counsel
"expose to the jury the facts from which jurors, as the sole
triers of fact and credibility, could appropriately draw inferences
relating to the reliability of the witness."
As the Court stated in Davis, supra,
at 415 U. S. 315
"[c]onfrontation means more than being allowed to confront the
witness physically." Consequently, in Davis,
as in other
cases involving trial court restrictions on the scope of
cross-examination, the Court has recognized that Confrontation
Clause questions will arise because such restrictions may
"effectively . . . emasculate the right of cross-examination
itself." Smith v. Illinois, 390 U.
, 390 U. S. 131
This case falls in neither category. It is outside the first
category, because the State made no attempt to introduce an
out-of-court statement by Agent Robillard for any purpose, let
alone as hearsay. Therefore, the restrictions the Confrontation
Clause places on "the range of admissible hearsay," Roberts,
at 448 U. S. 65
are not called into play.
The second category is also inapplicable here, for the trial
court did not limit the scope or nature of defense counsel's
cross-examination in any way. The Court has recognized that "the
cross-examiner is not only permitted to delve into the witness'
story to test the witness' perceptions and memory, but [also] . . .
allowed to impeach, i.e.,
discredit, the witness."
415 U.S. at 415 U. S. 316
But it does not follow that the right to cross-examine is denied by
the State whenever the witness' lapse of memory impedes one method
of discrediting him. Quite obviously, an expert witness who cannot
recall the basis for his opinion invites the jury to find that his
opinion is as unreliable as his memory. That the defense might
prefer the expert to embrace a particular theory, which it is
prepared to refute with special vigor, is irrelevant. "The main
and essential purpose of confrontation is to
Page 474 U. S.
for the opponent the opportunity of
at 415 U. S.
-316 (quoting 5 J. Wigmore, Evidence § 1395, p. 123
(3d ed.1940) (emphasis in original)). Generally speaking, the
Confrontation Clause guarantees an opportunity for effective
cross-examination, not cross-examination that is effective in
whatever way, and to whatever extent, the defense might wish.
448 U.S. at 448 U. S. 73
12 (even where the only opportunity the defense has to
cross-examine the declarant is at a preliminary hearing, except in
"extraordinary cases" where defense counsel provided ineffective
representation at the earlier proceeding, "no inquiry into
effectiveness' is required"). This conclusion is confirmed by
the fact that the assurances of reliability our cases have found in
the right of cross-examination are fully satisfied in cases such as
this one, notwithstanding the witness' inability to recall the
basis for his opinion: the factfinder can observe the witness'
demeanor under cross-examination, and the witness is testifying
under oath and in the presence of the accused. See id. at
448 U. S. 63, n.
We need not decide whether there are circumstances in which a
witness' lapse of memory may so frustrate any opportunity for
cross-examination that admission of the witness' direct testimony
violates the Confrontation Clause. In this case, defense counsel's
cross-examination of Agent Robillard demonstrated to the jury that
Robillard could not even recall the theory on which his opinion was
based. Moreover, through its own expert witness, the defense was
able to suggest to the jury that Robillard had relied on a theory
which the defense expert considered baseless. The Confrontation
Clause certainly requires no more than this.
Although Green, supra,
involved a witness who professed
a lapse of memory on the stand, that case lends no support to
respondent. In pertinent part, Green
was a case in which a
minor named Porter informed a police officer of a transaction in
which he claimed Green supplied him with drugs. At trial, Porter
professed to be unable to recall how he obtained
Page 474 U. S. 21
the drugs. The prosecution then introduced Porter's prior
inconsistent statements as substantive evidence. Green,
399 U.S. at 399 U. S. 152
This Court held that
"the Confrontation Clause does not require excluding from
evidence the prior statements of a witness who concedes making the
statements, and who may be asked to defend or otherwise explain the
inconsistency between his prior and his present version of the
events in question, thus opening himself to full cross-examination
at trial as to both stories."
at 399 U. S. 164
However, the Court also concluded that, in the posture of that
case, it would be premature to reach the question
"[w]hether Porter's apparent lapse of memory so affected Green's
right to cross-examine as to make a critical difference in the
application of the Confrontation Clause. . . ."
at 399 U. S. 168
In this connection, the Court noted that even some who argue that
"prior statements should be admissible as substantive evidence"
believe that this rule should not apply to "the case of a witness
who disclaims all present knowledge of the ultimate event," because
"in such a case the opportunities for testing the prior statement
through cross-examination at trial may be significantly
at 399 U. S. 169
n. 18 (citations omitted).
We need not decide today the question raised but not resolved in
framing of that question
indicates, the issue arises only where a "prior statement," not
itself subjected to cross-examination and the other safeguards of
testimony at trial, is admitted as substantive evidence. Since
there is no such out-of-court statement in this case, the adequacy
of a later opportunity to cross-examine, as a substitute for
cross-examination at the time the declaration was made, is not in
Under the Court's cases, then, Agent Robillard's inability to
recall on the stand the basis for his opinion presents none of the
perils from which the Confrontation Clause protects defendants in
criminal proceedings. The Confrontation Clause includes no
guarantee that every witness called by the
Page 474 U. S. 22
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. Accordingly, we hold that the admission
into evidence of Agent Robillard's opinion did not offend the
Confrontation Clause despite his inability to recall the basis for
The Delaware Supreme Court also appears to have believed that
the prosecution breached its "serious obligation not to obstruct a
criminal defendant's cross-examination of expert testimony," 493
A.2d at 963, seemingly because the prosecution knew in advance that
Agent Robillard would be unable to recall the basis for his opinion
when he testified at trial. While we would agree that Robillard's
testimony at the voir dire
examination must be taken to
have alerted both the prosecution and the defense to his lapse of
App. to Brief in Opposition A-1, we do not
think the prosecution was obliged to refrain from calling Robillard
unless it could somehow refresh his recollection. Whether or not,
under state law, Robillard's opinion should have been admitted into
evidence, nothing in the Federal Constitution forbids the
conclusion reached by the trial court in this case: that the
expert's inability to recall the basis for his opinion went to the
weight of the evidence, not its admissibility. See United
States v. Bastanipour,
697 F.2d 170, 176-177 (CA7 1982),
460 U.S. 1091 (1983). That being so, the
prosecution's foreknowledge that its expert would be unable to give
the precise basis for his opinion did not impose an obligation on
it, as a matter of due process, to refrain from introducing the
expert's testimony unless the basis for that testimony could
definitely be ascertained. We need not decide whether the
introduction of an expert opinion with no basis could ever be so
lacking in reliability, and so prejudicial, as to
Page 474 U. S. 23
deny a defendant a fair trial. The testimony of Dr. DeForest,
suggesting the actual basis for Robillard's opinion and vigorously
disputing its validity, utterly dispels any possibility of such a
claim in this case.
The petition for certiorari is granted, the judgment of the
Delaware Supreme Court is reversed, and the case is remanded to
that court for further proceedings not inconsistent with this
It is so ordered.
JUSTICE MARSHALL dissents from this summary disposition, which
has been ordered without affording the parties prior notice or an
opportunity to file briefs on the merits. See Maggio v.
Fulford, 462 U. S. 111
462 U. S.
-121 (1983) (MARSHALL, J., dissenting); Wyrick v.
Fields, 459 U. S. 42
459 U. S. 51
(1982) (MARSHALL, J., dissenting).
JUSTICE BLACKMUN would grant certiorari and give this case
JUSTICE STEVENS, concurring in the judgment.
Summary reversal of a state supreme court's application of
federal constitutional strictures to its own police and prosecutors
in novel cases of this kind tends to stultify the orderly
development of the law. Because I believe this Court should allow
state courts some latitude in the administration of their criminal
law, [Footnote 1
] I voted to
deny certiorari. Cf. California v. Carney, 471 U.
, 471 U. S. 395
(1985) (STEVENS, J., dissenting).
On the merits, I find the issue much closer to the question
reserved in California v. Green, 399 U.
, 399 U. S.
Page 474 U. S. 24
(1970), than does the Court. The question reserved in
concerned the admissibility of an earlier
out-of-court statement by the witness Porter of which Porter
disclaimed any present recollection at the time of trial. [Footnote 2
] The question decided by the
Court today concerns the admissibility of an earlier out-of-court
conclusion reached by a witness who disclaims any present
recollection of the basis
for that conclusion. The reasons
for carefully reserving the question in Green
that this case should not be decided without full argument.
Nevertheless, because the Court has granted certiorari and decided
to act summarily, because I am not persuaded that the Federal
Constitution was violated, and because the State Supreme Court
remains free to reinstate its judgment on the basis of its
interpretation of state law, I reluctantly concur in the
In California v. Green, 399 U.
, 399 U. S. 171
(1970), THE CHIEF JUSTICE wrote separately "to emphasize the
importance of allowing the States to experiment and innovate,
especially in the area of criminal justice." He correctly observed
"neither the Constitution as originally drafted, nor any
amendment, nor indeed any need, dictates that we must have absolute
uniformity in the criminal law in all the States."
at 399 U. S.
"Whether Porter's apparent lapse of memory so affected Green's
right to cross-examine as to make a critical difference in the
application of the Confrontation Clause in this case is an issue
which is not ripe for decision at this juncture."
(Footnote omitted.) Id.
at 399 U. S.
-169. See also id.
at 399 U. S. 169