(Slip Opinion)              OCTOBER TERM, 2023                                       1

                                       Syllabus

         NOTE: Where it is feasible, a syllabus (headnote) will be released, as is
       being done in connection with this case, at the time the opinion is issued.
       The syllabus constitutes no part of the opinion of the Court but has been
       prepared by the Reporter of Decisions for the convenience of the reader.
       See United States v. Detroit Timber & Lumber Co., 

.


SUPREME COURT OF THE UNITED STATES

                                       Syllabus

                            SMITH v. ARIZONA

      CERTIORARI TO THE COURT OF APPEALS OF ARIZONA,
                       DIVISION ONE

     No. 22–899.     Argued January 10, 2024—Decided June 21, 2024
The Sixth Amendment’s Confrontation Clause guarantees a criminal de-
  fendant the right to confront the witnesses against him. In operation,
  the Clause protects a defendant’s right of cross-examination by limit-
  ing the prosecution’s ability to introduce statements made by people
  not in the courtroom. The Clause thus bars the admission at trial of
  an absent witness’s statements unless the witness is unavailable and
  the defendant had a prior chance to subject her to cross-examination.
  Crawford v. Washington, 

, 53–54. This prohibition “ap-
  plies only to testimonial hearsay,” Davis v. Washington, 

, and in that two-word phrase are two limits. First, in speaking
  about “witnesses”—or “those who bear testimony”—the Clause con-
  fines itself to “testimonial statements,” a category this Court has vari-
  ously described. 

. Second, the Clause bars only the
  introduction of hearsay—meaning, out-of-court statements offered “to
  prove the truth of the matter asserted.” Anderson v. United States,
  

. Relevant here, the Confrontation Clause applies
  in full to forensic evidence. For example, in Melendez-Diaz v. Massa-
  chusetts, 

, prosecutors introduced “certificates of analy-
  sis” stating that lab tests had identified a substance seized from the
  defendant as cocaine. The Court held that the defendant had a right
  to cross-examine the lab analysts who prepared the certificates. In
  Bullcoming v. New Mexico, 

, the Court relied on Melen-
  dez-Diaz to hold that a State could not introduce one lab analyst’s writ-
  ten findings through the testimony of a substitute analyst. Finally, in
  Williams v. Illinois, 

, the Court considered a case where
  one lab analyst related an absent analyst’s findings on the way to stat-
  ing her own conclusion. The state court held that the testimony did
  not implicate the Confrontation Clause because the absent analyst’s
2                           SMITH v. ARIZONA

                                  Syllabus

    statements were introduced not for their truth, but to explain the basis
    for the testifying expert’s opinion. Five Members of the Court rejected
    that reasoning. But because one of those five affirmed the state court
    on alternative grounds, Williams lost.
       This case presents the same question on which the Court fractured
    in Williams. Arizona law enforcement officers found petitioner Jason
    Smith with a large quantity of what appeared to be drugs and drug-
    related items. Smith was charged with various drug offenses, and the
    State sent the seized items to a crime lab for scientific analysis. Ana-
    lyst Elizabeth Rast ran forensic tests on the items and concluded that
    they contained usable quantities of methamphetamine, marijuana,
    and cannabis. Rast prepared a set of typed notes and a signed report
    about the testing. The State originally planned for Rast to testify
    about those matters at Smith’s trial, but Rast stopped working at the
    lab prior to trial. So the State substituted another analyst, Greggory
    Longoni, to “provide an independent opinion on the drug testing per-
    formed by Elizabeth Rast.” At trial, Longoni conveyed to the jury what
    Rast’s records revealed about her testing, before offering his “inde-
    pendent opinion” of each item’s identity. Smith was convicted. On
    appeal, he argued that the State’s use of a substitute expert to convey
    the substance of Rast’s materials violated his Confrontation Clause
    rights. The Arizona Court of Appeals rejected Smith’s challenge, hold-
    ing that Longoni could constitutionally present his own expert opin-
    ions based on his review of Rast’s work because her statements were
    then used only to show the basis of his opinion and not to prove their
    truth.
Held: When an expert conveys an absent analyst’s statements in support
 of the expert’s opinion, and the statements provide that support only
 if true, then the statements come into evidence for their truth. Pp. 11–
 22.
     (a) The parties agree that Smith’s confrontation claim can succeed
 only if Rast’s statements came into evidence for their truth. Smith
 argues that the condition is satisfied here because her statements were
 conveyed, via Longoni’s testimony, to establish that what she said hap-
 pened in the lab did in fact happen. The State contends that Rast’s
 statements came into evidence not for their truth, but to “show the
 basis” of Longoni’s independent opinion. It emphasizes that Arizona’s
 Rules of Evidence authorize the admission of such statements for that
 limited purpose. Evidentiary rules, however, do not control the in-
 quiry into whether a statement is admitted for its truth. Instead,
 courts must conduct an independent analysis of that question.
     Truth is everything when it comes to the kind of basis testimony
 presented here. If an expert conveys an out-of-court statement in sup-
 port of his opinion, and the statement supports that opinion only if
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                                Syllabus

  true, then the statement has been offered for the truth of what it as-
  serts. The truth of the basis testimony is what makes it useful to the
  State; that is what supplies the predicate for—and thus gives value
  to—the state expert’s opinion. And from the factfinder’s perspective,
  the jury cannot decide whether the expert’s opinion is credible without
  evaluating the truth of the factual assertions on which it is based. But
  that is what raises the Confrontation Clause problem. For the defend-
  ant has no opportunity to challenge the veracity of the out-of-court as-
  sertions that are doing much of the work.
     Here, Rast’s statements came in for their truth, and no less because
  they were admitted to show the basis of Longoni’s expert opinions. All
  of Longoni’s opinions were predicated on the truth of Rast’s factual
  statements. And the jury could credit those opinions because it too
  accepted the truth of what Rast reported about her lab work. So the
  State’s basis evidence—more precisely, the truth of the statements on
  which its expert relied—propped up the whole case; yet the maker of
  the statements was not in the courtroom, and Smith could not ask her
  any questions. Pp. 11–19.
     (b) What remains is whether the out-of-court statements Longoni
  conveyed were testimonial. The testimonial issue focuses on the “pri-
  mary purpose” of the statement, and in particular on how it relates to
  a future criminal proceeding. But that issue is not now fit for resolu-
  tion by this Court. The question presented in Smith’s petition for cer-
  tiorari took as a given that Rast’s out-of-court statements were testi-
  monial, and the Arizona Court of Appeals did not decide the issue.
  Indeed, there may not remain a matter to decide, as Smith maintains
  that the State has forfeited any argument that Rast’s statements were
  not testimonial. The testimonial issue, including the threshold forfei-
  ture question, is thus best considered by the state court in the first
  instance. Pp. 19–22.
Vacated and remanded.

  KAGAN, J., delivered the opinion of the Court, in which SOTOMAYOR,
KAVANAUGH, BARRETT, and JACKSON, JJ., joined, and in which THOMAS
and GORSUCH, JJ., joined as to Parts I, II, and IV. THOMAS, J., and GOR-
SUCH, J., filed opinions concurring in part. ALITO, J., filed an opinion
concurring in the judgment, in which ROBERTS, C. J., joined.
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                             Opinion of the Court

     NOTICE: This opinion is subject to formal revision before publication in the
     United States Reports. Readers are requested to notify the Reporter of
     Decisions, Supreme Court of the United States, Washington, D. C. 20543,
     [email protected], of any typographical or other formal errors.


SUPREME COURT OF THE UNITED STATES
                                   _________________

                                   No. 22–899
                                   _________________


        JASON SMITH, PETITIONER v. ARIZONA
  ON WRIT OF CERTIORARI TO THE COURT OF APPEALS OF
                ARIZONA, DIVISION ONE
                                 [June 21, 2024]

   JUSTICE KAGAN delivered the opinion of the Court.
   The Sixth Amendment’s Confrontation Clause guaran-
tees a criminal defendant the right to confront the wit-
nesses against him. The Clause bars the admission at trial
of “testimonial statements” of an absent witness unless she
is “unavailable to testify, and the defendant ha[s] had a
prior opportunity” to cross-examine her. Crawford v. Wash-
ington, 

, 53–54 (2004). And that prohibition
applies in full to forensic evidence. So a prosecutor cannot
introduce an absent laboratory analyst’s testimonial out-of-
court statements to prove the results of forensic testing.
See Melendez-Diaz v. Massachusetts, 

 (2009).
   The question presented here concerns the application of
those principles to a case in which an expert witness re-
states an absent lab analyst’s factual assertions to support
his own opinion testimony. This Court has held that the
Confrontation Clause’s requirements apply only when the
prosecution uses out-of-court statements for “the truth of
the matter asserted.” Crawford, 

.
Some state courts, including the court below, have held that
this condition is not met when an expert recites another an-
alyst’s statements as the basis for his opinion. Today, we
2                     SMITH v. ARIZONA

                      Opinion of the Court

reject that view. When an expert conveys an absent ana-
lyst’s statements in support of his opinion, and the state-
ments provide that support only if true, then the state-
ments come into evidence for their truth. As this dispute
illustrates, that will generally be the case when an expert
relays an absent lab analyst’s statements as part of offering
his opinion. And if those statements are testimonial too—
an issue we briefly address but do not resolve as to this
case—the Confrontation Clause will bar their admission.
                               I
                               A
   The Confrontation Clause provides that “[i]n all criminal
prosecutions, the accused shall enjoy the right . . . to be con-
fronted with the witnesses against him.” In operation, the
Clause protects a defendant’s right of cross-examination by
limiting the prosecution’s ability to introduce statements
made by people not in the courtroom. For a time, this Court
held that the Clause’s “preference for face-to-face” confron-
tation could give way if a court found that an out-of-court
statement bore “adequate indicia of reliability.” Ohio v.
Roberts, 

, 65–66 (1980). But two decades ago,
the Court changed course, to better reflect original under-
standings. In Crawford v. Washington, the Court deemed
it “fundamentally at odds with the right of confrontation”
to admit statements based on judicial determinations of re-
liability. 

. The Clause, Crawford explained,
“commands[ ] not that evidence be reliable, but that relia-
bility be assessed in a particular manner: by testing in the
crucible of cross-examination.” 

 And so the Clause
bars the admission at trial of an absent witness’s state-
ments—however trustworthy a judge might think them—
unless the witness is unavailable and the defendant had a
prior chance to subject her to cross-examination.
   But not always. The Clause’s prohibition “applies only to
testimonial hearsay”—and in that two-word phrase are two
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                      Opinion of the Court

limits. Davis v. Washington, 

 (2006).
First, in speaking about “witnesses”—or “those who bear
testimony”—the Clause confines itself to “testimonial state-
ments,” a category whose contours we have variously de-
scribed. 

; see 

 (statements “made
in the course of police interrogation” were testimonial when
“the primary purpose of the interrogation [was] to establish
or prove past events potentially relevant to later criminal
prosecution”); Michigan v. Bryant, 

(2011) (statements made to police “to meet an ongoing
emergency” were “not procured with a primary purpose of
creating an out-of-court substitute for trial testimony”);
Melendez-Diaz, 

 (testimonial certificates of
the results of forensic analysis were created “under circum-
stances which would lead an objective witness reasonably
to believe that the statement[s] would be available for use
at a later trial”); infra, at 19. Second and more relevant
here, the Clause bars only the introduction of hearsay—
meaning, out-of-court statements offered “to prove the
truth of the matter asserted.” Anderson v. United States,

 (1974). When a statement is admitted
for a reason unrelated to its truth, we have held, the
Clause’s “role in protecting the right of cross-examination”
is not implicated. Tennessee v. Street, 

(1985); see Anderson, 

. That is because the
need to test an absent witness ebbs when her truthfulness
is not at issue. See ibid.; Street, 

; infra, at
13–14, 17.
   Not long after Crawford, the Court made clear that the
Confrontation Clause applies to forensic reports. In Melendez-
Diaz v. Massachusetts, state prosecutors introduced “certif-
icates of analysis” (essentially, affidavits) stating that lab
tests had identified a substance seized from the defendant
as cocaine. 

. But the State did not call as
witnesses the analysts who had conducted the tests and
4                     SMITH v. ARIZONA

                      Opinion of the Court

signed the certificates. We held that a “straightforward ap-
plication” of Crawford showed a constitutional violation.

. The certificates were testimonial: They
had an “evidentiary purpose,” identical to the one served
had the analysts given “live, in-court testimony.” 

. And the certificates were offered to prove the truth of
what they asserted: that the seized powder was in fact co-
caine. See 

 at 310–311. So the defendant had a right
to cross-examine the lab-analyst certifiers. In reaching
that conclusion, we rejected the State’s claim that the re-
sults of so-called “neutral, scientific testing” should be sub-
ject to a different rule. 

. We again underscored
that the Confrontation Clause commanded not reliability
but one way of testing it—through cross-examination. See

 And we thought that method might have plenty to do
in cases involving forensic analysis. After all, lab tests are
“not uniquely immune from the risk of manipulation” or
mistake. 

. The defendant might have used cross-
examination to probe “what tests the analysts performed,”
whether those tests “present[ed] a risk of error,” and
whether the analysts had the right skill set to “interpret[ ]
their results.” 

.
  Two years later, the Court relied on Melendez-Diaz to
hold that a State could not introduce one lab analyst’s writ-
ten findings through the testimony of another. In Bullcom-
ing v. New Mexico, 

, 651–652 (2011), an ana-
lyst tested the blood-alcohol level of someone charged with
drunk driving, and prepared a “testimonial certification” re-
porting that the level was higher than legal. But by the
time the driver’s trial began, that analyst had been placed
on unpaid leave. So the State instead called a different an-
alyst from the same lab to testify as to what the certification
said. The substitute analyst had similar qualifications, and
knew about the type of test performed. But the Court held
that insufficient to satisfy the Confrontation Clause. The
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                     Opinion of the Court

“surrogate testimony,” the Court explained, “could not con-
vey what [the certifying analyst] knew or observed” about
“the particular test and testing process he employed.” Id.,
at 661. Nor could that “testimony expose any lapses or lies
on the certifying analyst’s part,” or offer any insight into
whether his leave-without-pay was the result of miscon-
duct. Id., at 662. Concluded the Court: “[W]hen the State
elected to introduce [the] certification,” its author—and not
any substitute—“became [the] witness [that the defendant]
had the right to confront.” Id., at 663.
   The very next Term brought another case in which one
lab analyst related what another had found—though this
time on the way to stating her own conclusion. In Williams
v. Illinois, 

 (2012), state police sent vaginal
swabs from a rape victim known as L. J. to a private lab for
DNA testing. When the lab sent back a DNA profile, a state
analyst checked it against the police department’s database
and found that it matched the profile of prior arrestee
Sandy Williams. The State charged Williams with the rape,
and he went to trial. The prosecution chose not to bring the
private lab analyst to the stand. Instead, it called Sandra
Lambatos, the state analyst who had searched the police
database and found the DNA match. Lambatos had no
first-hand knowledge of how the private lab had produced
its results; she did not even know whether those results ac-
tually came from L. J.’s vaginal swabs (as opposed to some
other sample). But she spoke repeatedly about comparing
Williams’s DNA to the DNA “found in [L. J.’s] vaginal
swabs.” 

 (plurality opinion); see 

(KAGAN, J., dissenting). So in addition to describing how
she discovered a match, Lambatos became the conduit for
what a different analyst had reported—that a particular
DNA profile came from L. J.’s vaginal swabs. Williams ob-
jected, at trial and later: He thought that, just as in Bull-
coming, crucial evidence had been admitted through a sur-
rogate expert, thus violating his right of confrontation.
6                     SMITH v. ARIZONA

                      Opinion of the Court

   But the Illinois Supreme Court rejected Williams’s claim,
holding that Lambatos’s testimony about the private lab
analyst’s finding did not raise a Confrontation Clause issue.
See People v. Williams, 

, 143–144, 

, 278–279 (2010). The court explained that under
state evidence law, an expert can disclose “underlying facts
and data” for “the purpose of explaining the basis for [her]
opinion.” 

, 939 N. E. 2d, at 274–275, 278.
And when she does so, the court held, the testimony is not
subject to the Confrontation Clause because it is not admit-
ted “for the truth of the matter asserted.” 

, 

. Thus, Lambatos could relay the private
lab’s finding that L. J.’s vaginal swabs produced a certain
DNA profile in order to “explain[ ] the basis for her opinion”
that “there was a DNA match between [Williams’s] blood
sample and the semen sample recovered from L. J.” 

, 

. The admission of the private lab
report’s contents for that “limited purpose,” the court rea-
soned, would “aid the [factfinder] in assessing the value of
[Lambatos’s] opinion.” 

, 

; see

, 

.
   This Court granted Williams’s petition for certiorari, but
failed to produce a majority opinion. Four Members of the
Court approved the Illinois Supreme Court’s approach to
“basis evidence,” and agreed that Lambatos’s recitation of
the private lab’s findings served “the legitimate nonhearsay
purpose of illuminating the expert’s thought process.” Wil-
liams, 

 (plurality opinion). But the remain-
ing five Members rejected that view. Those five stated, in
two opinions, that basis evidence is generally introduced for
its truth, and was so introduced at Williams’s trial.
JUSTICE THOMAS explained that “the purportedly limited
reason for [the basis] testimony—to aid the factfinder in
evaluating the expert’s opinion—necessarily entail[ed] an
evaluation of whether [that] testimony [was] true”: “[T]he
validity of Lambatos’[s] opinion ultimately turned on the
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                          Opinion of the Court

truth of [the private lab analyst’s] statements.” Id., at 106,
n. 1, 108 (concurring in judgment). A dissent for another
four Justices agreed: “[T]he utility of the [private analyst’s]
statement that Lambatos repeated logically depended on its
truth.” Id., at 132 (opinion of KAGAN, J.). And the State
could not avoid that conclusion by “rely[ing] on [Lamba-
tos’s] status as an expert.” Id., at 126. Those shared views
might have made for a happy majority, except that a differ-
ent Confrontation Clause issue intruded. JUSTICE THOMAS
thought that the private lab report was not testimonial be-
cause it lacked sufficient formality, so affirmed the Illinois
Supreme Court on that alternative ground. The bottom line
was that Williams lost, even though five Members of this
Court rejected the state court’s “not for the truth” reason-
ing.1
   Our opinions in Williams “have sown confusion in courts
across the country” about the Confrontation Clause’s appli-
cation to expert opinion testimony. Stuart v. Alabama, 

, ___ (2018) (GORSUCH, J., dissenting from denial
of certiorari) (slip op., at 2). Some courts have applied the
Williams plurality’s “not for the truth” reasoning to basis
testimony, while others have adopted the opposed five-Jus-
tice view.2 This case emerged out of that muddle.
——————
  1 The Court also failed to reach agreement on the testimonial issue.

The four Justices who accepted the state court’s “not for the truth” view
also concluded that the report was not testimonial. See Williams, 567
U. S., at 81–86 (plurality opinion). But they did so for reasons different
from JUSTICE THOMAS’s. Compare ibid. with id., at 110–117 (opinion con-
curring in judgment). The result was that no single rationale for affir-
mance garnered a majority.
  2 Compare, e.g., State v. Mercier, 

, ¶¶12–14, 

 (accepting the “not for the truth” rationale for admitting an expert’s
basis testimony); State v. Hutchison, 

 (Tenn. 2016);
United States v. Murray, 

 (CA11 2013), with Peo-
ple v. Sanchez, 

, 

 (2016) (rejecting
the “not for the truth” rationale for admitting an expert’s basis testi-
mony); Martin v. State, 

 (Del. 2013); Young v. United
States, 

 (D. C. 2013); Leidig v. State, 

,
8                        SMITH v. ARIZONA

                         Opinion of the Court

                               B
   Like Melendez-Diaz, this case involves drugs. In Decem-
ber 2019, Arizona law enforcement officers executed a
search warrant on a property in the foothills of Yuma
County. Inside a shed on the property, they found peti-
tioner Jason Smith. They also found a large quantity of
what appeared to be drugs and drug-related items. As a
result, Smith was charged with possessing dangerous drugs
(methamphetamine) for sale; possessing marijuana for sale;
possessing narcotic drugs (cannabis) for sale; and pos-
sessing drug paraphernalia. He pleaded not guilty, and the
case was set for trial.
   In preparation, the State sent items seized from the shed
to a crime lab run by the Arizona Department of Public
Safety (DPS) for a “full scientific analysis.” App. to Pet. for
Cert. 127a. The State’s request identified Smith as the in-
dividual “associated” with the substances, listed the
charges against him, and noted that “[t]rial ha[d] been set.”

 Analyst Elizabeth Rast communicated with prosecu-
tors about exactly which items needed to be examined, and
then ran the requested tests. See 

 at 99a.
   Rast prepared a set of typed notes and a signed report,
both on DPS letterhead, about the testing. The notes docu-
mented her lab work and results. They disclosed, for each
of eight items: a “[d]escription” of the item; the weight of
the item and how the weight was measured; the test(s) she
performed on the item, including whether she first ran a
“[b]lank” on the testing equipment; the results of those
tests; and a “[c]onclusion” about the item’s identity. See 

at 88a–98a. The signed report then distilled the notes into
two pages of ultimate findings, denoted “results/interpreta-
tions.” See 

 at 85a–87a. After listing the eight items,
the report stated that four “[c]ontained a usable quantity of
——————
234, n. 23, 

, 901, n. 23 (2021); Commonwealth v. Jones, 

, 

 (2015).
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                      Opinion of the Court

methamphetamine,” three “[c]ontained a usable quantity of
marijuana,” and one “[c]ontained a usable quantity of can-
nabis.” Id., at 86a–87a. The State originally planned for
Rast to testify about those matters at Smith’s trial.
   But with three weeks to go, the State called an audible,
replacing Rast with a different DPS analyst as its expert
witness. In the time between testing and trial, Rast had
stopped working at the lab, for unexplained reasons. And
the State chose not to rely on the now-former employee as
a witness. So the prosecutors filed an amendment to their
“final pre-trial conference statement” striking out the name
Elizabeth Rast and adding “Greggory Longoni, forensic sci-
entist (substitute expert).” Id., at 26a. Longoni had no
prior connection to the Smith case, and the State did not
claim otherwise. Its amendment simply stated that “Mr.
Longoni will provide an independent opinion on the drug
testing performed by Elizabeth Rast.” Ibid. And it contin-
ued: “Ms. Rast will not be called. [Mr. Longoni] is expected
to have the same conclusion.” Ibid.
   And he did come to the same conclusion, in reliance on
Rast’s records. Because he had not participated in the
Smith case, Longoni prepared for trial by reviewing Rast’s
report and notes. And when Longoni took the stand, he re-
ferred to those materials and related what was in them,
item by item by item. As to each, he described the specific
“scientific method[s]” Rast had used to analyze the sub-
stance (e.g., a microscopic examination, a chemical color
test, a gas chromatograph/mass spectrometer test). Id., at
41a; see id., at 42a, 46a–48a. And as to each, he stated that
the testing had adhered to “general principles of chemis-
try,” as well as to the lab’s “policies and practices,” id., at
47a–48a; see id., at 40a; so he noted, for example, that Rast
had run a “blank” to confirm that testing equipment was
not contaminated, id., at 42a, 47a. After thus telling the
jury what Rast’s records conveyed about her testing of the
items, Longoni offered an “independent opinion” of their
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                      Opinion of the Court

identity. Id., at 46a–47a, 49a. More specifically, the opin-
ions he offered were: that Item 26 was “a usable quantity of
marijuana,” that Items 20A and 20B were “usable quan-
tit[ies] of methamphetamine,” and that Item 28 was “[a] us-
able quantity of cannabis.” Ibid.
   After Smith was convicted, he brought an appeal focusing
on Longoni’s testimony. In Smith’s view, the State’s use of
a “substitute expert”—who had not participated in any of
the relevant testing—violated his Confrontation Clause
rights. Id., at 26a; see Brief for Appellant Smith in No. 1
CA–CR 21–0451 (Ariz. Ct. App.), pp. 20–23. The real wit-
ness against him, Smith urged, was Rast, through her writ-
ten statements; but he had not had the opportunity to cross-
examine her. See ibid. The State disagreed. In its view,
Longoni testified about “his own independent opinions,”
even though making use of Rast’s records. Brief for Appel-
lee Arizona in No. 1 CA–CR 21–0451 (Ariz. Ct. App.), p. 22.
So Longoni was the only witness Smith had a right to con-
front. See ibid.
   The Arizona Court of Appeals affirmed Smith’s convic-
tions, rejecting his Confrontation Clause challenge. It re-
lied on Arizona precedent (similar to the Illinois Supreme
Court’s decision in Williams) stating that an expert may
testify to “the substance of a non-testifying expert’s analy-
sis, if such evidence forms the basis of the [testifying] ex-
pert’s opinion.” App. to Pet. for Cert. 11a–12a (quoting
State ex rel. Montgomery v. Karp, 

, 

 (App. 2014)). That is because, the Arizona
courts have said, the “underlying facts” are then “used only
to show the basis of [the in-court witness’s] opinion and not
to prove their truth.” Ibid., 

. On that view,
the Court of Appeals held, Longoni could constitutionally
“present[ ] his independent expert opinions” as “based on
his review of Rast’s work.” App. to Pet. for Cert. 11a.
   We granted certiorari to consider that reasoning, 600
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                          Opinion of the Court

U. S. ___ (2023), and we now reject it.3
                              II
   Smith’s confrontation claim can succeed only if Rast’s
statements came into evidence for their truth. As earlier
explained, the Clause applies solely to “testimonial hear-
say.” Davis, 

 (emphasis added); see supra,
at 3. And that means the Clause “does not bar the use of
testimonial statements for purposes other than establish-
ing the truth of the matter asserted.” Crawford, 

. So a court analyzing a confrontation claim must
identify the role that a given out-of-court statement—here,
Rast’s statements about her lab work—served at trial. On
that much, indeed, the entire Williams Court agreed. Amid
all the fracturing that case produced, every Justice defined
its primary question in the same way: whether the absent
analyst’s statements were introduced for their truth. See
567 U. S., at 57–58 (plurality opinion); 

 (THOMAS,
J., concurring in judgment); 

 at 125–126 (KAGAN, J., dis-
senting). The parties here likewise concur in that framing.
See Brief for Smith 28–29; Brief for Arizona 17–18. If Rast’s

——————
  3 The question on which we granted certiorari made reference as well

to another aspect of the Court of Appeals’ reasoning. That question asks
whether the Confrontation Clause permits “testimony by a substitute ex-
pert conveying the testimonial statements of a nontestifying forensic an-
alyst, on the grounds that (a) the testifying expert offers some independ-
ent opinion and the analyst’s statements are offered not for their truth
but to explain the expert’s opinion, and (b) the defendant did not inde-
pendently seek to subpoena the analyst.” Pet. for Cert. i. The “(b)” in
that question arises from the following sentence in the court’s opinion:
“Had Smith sought to challenge Rast’s analysis, he could have called her
to the stand and questioned her, but he chose not to do so.” App. to Pet.
for Cert. 12a. We need not spend much time on that rationale because
the State rightly does not defend it. As we held in Melendez-Diaz, a de-
fendant’s “ability to subpoena” an absent analyst “is no substitute for the
right of confrontation.” 

. The Confrontation Clause “im-
poses a burden on the prosecution to present its witnesses, not on the
defendant to bring those adverse witnesses into court.” 

12                      SMITH v. ARIZONA

                        Opinion of the Court

statements came in to establish the truth of what she said,
then the Clause’s alarms begin to ring; but if her state-
ments came in for another purpose, then those alarms fall
quiet.
   Where the parties disagree, of course, is in answering
that purpose question. Smith argues that the “for the
truth” condition is satisfied here, just as much as in
Melendez-Diaz or Bullcoming. See Brief for Smith 23–28;
supra, at 3–5. In his view, Rast’s statements were con-
veyed, via Longoni’s testimony, to establish that what she
said happened in the lab did in fact happen. Or put more
specifically, those statements were conveyed to show that
she used certain standard procedures to run certain tests,
which enabled identification of the seized items. The State
sees the matter differently. See Brief for Arizona 19–26.
Echoing the Arizona Court of Appeals (and the Illinois Su-
preme Court in Williams), the State argues that Rast’s
statements came into evidence not for their truth, but in-
stead to “show the basis” of the in-court expert’s independ-
ent opinion. Brief for Arizona 21; see supra, at 6. And to
defend that characterization, Arizona emphasizes that its
Rule of Evidence 703 (again, like Illinois’s) authorizes the
admission of such statements only for that purpose—i.e., to
“help[ ] the jury [to] evaluate” the opinion testimony. Brief
for Arizona 20–21; see post, at 8 (ALITO, J., concurring in
judgment) (arguing the same as to Federal Rule of Evidence
703).
   Evidentiary rules, though, do not control the inquiry into
whether a statement is admitted for its truth. That inquiry,
as just described, marks the scope of a federal constitu-
tional right. See supra, at 11. And federal constitutional
rights are not typically defined—expanded or contracted—
by reference to non-constitutional bodies of law like evi-
dence rules.4 The confrontation right is no different, as
——————
 4 One qualification is appropriate. If an evidentiary rule reflects a
                     Cite as: 

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                         Opinion of the Court

Crawford made clear. “Where testimonial statements are
involved,” that Court explained, “the Framers [did not
mean] to leave the Sixth Amendment’s protection to the va-
garies of the rules of evidence.” 

. JUSTICE
THOMAS reiterated the point in Williams: “[C]oncepts cen-
tral to the application of the Confrontation Clause are ulti-
mately matters of federal constitutional law that are not
dictated by state or federal evidentiary rules.” 

 (opinion concurring in judgment). We therefore do not
“accept [a State’s] nonhearsay label at face value.” 

; see 

 (KAGAN, J., dissenting). Instead, we con-
duct an independent analysis of whether an out-of-court
statement was admitted for its truth, and therefore may
have compromised a defendant’s right of confrontation.
  We did just that in Tennessee v. Street—and in so doing
showcased how an out-of-court statement can come into ev-
idence for a non-truth-related reason. See 471 U. S., at
410–417. Street was charged with murder, based mostly on
a stationhouse confession. At trial, he claimed that the con-
fession was coerced, and in a peculiar way: The sheriff, he
said, had read aloud an accomplice’s confession and forced
him to repeat it. On rebuttal, the State introduced the
other confession (through the sheriff ’s testimony) to
demonstrate to the jury all the ways its content deviated
from Street’s. We upheld that use as “nonhearsay.” Id., at
413. The other confession came in, we explained, not to
prove “the truth of [the accomplice’s] assertions” about how
the murder happened, but only to disprove Street’s claim
about how the sheriff elicited his own confession. Ibid. Or
——————
long-established understanding, then it might shed light on the histori-
cal meaning of the Confrontation Clause. But that could not possibly be
said of Rule 703—the rule Arizona cites to support the introduction of
basis evidence. On the contrary, that rule is a product of the late-20th
century, and was understood from the start to depart from past practice.
See Brief for Richard D. Friedman as Amicus Curiae 17; Advisory Com-
mittee’s Notes on Fed. Rule Evid. 703, 28 U. S. C. App., p. 393.
14                    SMITH v. ARIZONA

                      Opinion of the Court

otherwise said, the point was to show, by highlighting the
two confessions’ differences, that Street’s was not a “coerced
imitation.” Id., at 414. For that purpose, the truth of the
accomplice’s confession (and the credibility of the accom-
plice himself ) was irrelevant.
   But truth is everything when it comes to the kind of basis
testimony presented here. If an expert for the prosecution
conveys an out-of-court statement in support of his opinion,
and the statement supports that opinion only if true, then
the statement has been offered for the truth of what it as-
serts. How could it be otherwise? “The whole point” of the
prosecutor’s eliciting such a statement is “to establish—be-
cause of the [statement’s] truth—a basis for the jury to credit
the testifying expert’s” opinion. Stuart, 586 U. S., at ___
(GORSUCH, J., dissenting from denial of certiorari) (slip op.,
at 3) (emphasis in original). Or said a bit differently, the
truth of the basis testimony is what makes it useful to the
prosecutor; that is what supplies the predicate for—and
thus gives value to—the state expert’s opinion. So “[t]here
is no meaningful distinction between disclosing an out-of-
court statement” to “explain the basis of an expert’s opin-
ion” and “disclosing that statement for its truth.” Williams,

 (THOMAS, J., concurring in judgment). A
State may use only the former label, but in all respects the
two purposes merge.
   Or to see the point another way, consider it from the fact-
finder’s perspective. In the view of the Arizona courts, an
expert’s conveyance of another analyst’s report enables the
factfinder to “determine whether [the expert’s] opinion
should be found credible.” Karp, 

, 

; see Williams, 

, 

 (also stating that such a report “aid[s] the jury in
assessing the value of [the expert’s] opinion”); supra, at 6,
10. That is no doubt right. The jury cannot decide whether
the expert’s opinion is credible without evaluating the truth
of the factual assertions on which it is based. See D. Kaye,
                  Cite as: 

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                      Opinion of the Court

D. Bernstein, A. Ferguson, M. Wittlin, & J. Mnookin, The
New Wigmore: Expert Evidence §5.4.1, p. 271 (3d ed. 2021).
If believed true, that basis evidence will lead the jury to
credit the opinion; if believed false, it will do the opposite.
See Williams, 

, and n. 1 (THOMAS, J., con-
curring in judgment); 

 at 126–127 (KAGAN, J., dissent-
ing). But that very fact is what raises the Confrontation
Clause problem. For the defendant has no opportunity to
challenge the veracity of the out-of-court assertions that are
doing much of the work.
   And if that explanation seems a bit abstract, then take
this case as its almost-too-perfect illustration. Recall that
Rast tested eight seized items before she disappeared from
the scene. At trial, the prosecutor asked the State’s “sub-
stitute expert” Longoni to testify about four of them (with
the rest dropping out of the case). App. to Pet. for Cert. 26a.
A recap of their exchange about one item will be enough;
the rest followed the same pattern. Remember as you read
that Longoni, though familiar with the lab’s general prac-
tices, had no personal knowledge about Rast’s testing of the
seized items. Rather, as his testimony makes clear, what
he knew on that score came only from reviewing Rast’s rec-
ords. With that as background:
    Q Turn your attention to Item 26. I’m going to hand
    you what’s been marked as State’s Exhibit 98 [Rast’s
    notes]. . . . Did you review how [Item] 26 was tested in
    this case?
    A Yes.
    Q When you reviewed it, did you notice whether the
    [standard lab] policies and practices that you have just
    described were followed?
    A Yes.
    Q Were they followed?
    A Yes.
    .             .          .          .          .
16                    SMITH v. ARIZONA

                      Opinion of the Court

     Q From your review of the lab notes in this case, can
     you tell me what scientific method was used to analyze
     Item 26?
     A Yes.
     Q And what was used?
     A The microscopic examination and the chemical color
     test. . . .
     Q That was done in this case?
     A Yes, it was.
     Q Was there a blank done to prevent contamination,
     make sure everything was clean?
     A According to the notes, yes.
     .           .           .            .         .
     Q In reviewing what was done, your knowledge and
     training as a forensic scientist, your knowledge and ex-
     perience with DPS’s policies, practices, procedures,
     your knowledge of chemistry, the lab notes, the intake
     records, the chemicals used, the tests done, can you
     form an independent opinion on the identity of Item 26?
     A Yes.
     Q What is that opinion?
     A That is a usable quantity of marijuana.

 at 39a–42a, 46a. And then the prosecutor went on to
Items 20A, 20B, and 28, asking similar questions, receiving
similar answers based on Rast’s records, and finally elicit-
ing similar “independent opinions”—which were no more
than what Rast herself had concluded. See supra, at 8–9.
“Yes,” Longoni confirmed, just as Item 26 was a “usable
quantity of marijuana,” Items 20A and 20B were “usable
quantit[ies] of methamphetamine” and Item 28 was a “usa-
ble quantity of cannabis.” App. to Pet. for Cert. 46a, 47a,
49a.
  Rast’s statements thus came in for their truth, and no
less because they were admitted to show the basis of Lon-
goni’s expert opinions. All those opinions were predicated
                 Cite as: 

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                     Opinion of the Court

on the truth of Rast’s factual statements. Longoni could
opine that the tested substances were marijuana, metham-
phetamine, and cannabis only because he accepted the
truth of what Rast had reported about her work in the lab—
that she had performed certain tests according to certain
protocols and gotten certain results. And likewise, the jury
could credit Longoni’s opinions identifying the substances
only because it too accepted the truth of what Rast reported
about her lab work (as conveyed by Longoni). If Rast had
lied about all those matters, Longoni’s expert opinion would
have counted for nothing, and the jury would have been in
no position to convict. So the State’s basis evidence—more
precisely, the truth of the statements on which its expert
relied—propped up its whole case. But the maker of those
statements was not in the courtroom, and Smith could not
ask her any questions.
   Approving that practice would make our decisions in
Melendez-Diaz and Bullcoming a dead letter, and allow for
easy evasion of the Confrontation Clause. As earlier de-
scribed, those two decisions applied Crawford in “straight-
forward” fashion to forensic evidence. Melendez-Diaz, 

; see Bullcoming, 564 U. S., at 659–661; supra,
at 3–5. The first prevented the introduction of a lab ana-
lyst’s testimonial report sans lab analyst. The second re-
fused to accede to the idea that any old analyst—i.e., a sub-
stitute who had not taken part in the lab work—would do.
Arizona offers only a slight variation. On its view, a surro-
gate analyst can testify to all the same substance—that is,
someone else’s substance—as long as he bases an “inde-
pendent opinion” on that material. And that is true even if,
as here, the proffered opinion merely replicates, rather than
somehow builds on, the testing analyst’s conclusions. So
every testimonial lab report could come into evidence
through any trained surrogate, however remote from the
case. And no defendant would have a right to cross-examine
the testing analyst about what she did and how she did it
18                    SMITH v. ARIZONA

                      Opinion of the Court

and whether her results should be trusted. In short, Ari-
zona wants to end run all we have held the Confrontation
Clause to require. It cannot.
   Properly understood, the Clause still allows forensic ex-
perts like Longoni to play a useful role in criminal trials.
Because Longoni worked in the same lab as Rast, he could
testify from personal knowledge about how that lab typi-
cally functioned—the standards, practices, and procedures
it used to test seized substances, as well as the way it main-
tained chains of custody. (Indeed, Longoni did just that in
a different part of his testimony. See App. to Pet. for Cert.
32a–39a.) Or had he not been familiar with Rast’s lab, he
could have testified in general terms about forensic guide-
lines and techniques—perhaps explaining what it means
for a lab to be accredited and what requirements accredita-
tion imposes. Or as the Williams plurality and dissent both
observed, he might have been asked—and could have an-
swered—any number of hypothetical questions, taking the
form of: “If or assuming some out-of-court statement were
true, what would follow from it?” See 567 U. S., at 67–68;
id., at 129, n. 2. (The State of course would then have to
separately prove the thing assumed.) The United States,
appearing as amicus curiae in support of neither party, use-
fully addressed these matters at oral argument, distin-
guishing Longoni’s testimony as block-quoted above from
the various kinds of testimony just described. See Tr. of
Oral Arg. 36–41. The latter forms of testimony allow foren-
sic expertise to inform a criminal case without violating the
defendant’s right of confrontation. And we offer these
merely as examples; there may be others.
   But as the United States acknowledged, the bulk of Lon-
goni’s testimony took no such permissible form. Ibid. Here,
the State used Longoni to relay what Rast wrote down
about how she identified the seized substances. Longoni
thus effectively became Rast’s mouthpiece. He testified to
the precautions (she said) she took, the standards (she said)
                     Cite as: 

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                          Opinion of the Court

she followed, the tests (she said) she performed, and the re-
sults (she said) she obtained. The State offered up that ev-
idence so the jury would believe it—in other words, for its
truth. So if the out-of-court statements were also testimo-
nial, their admission violated the Confrontation Clause.
Smith would then have had a right to confront the person
who actually did the lab work, not a surrogate merely read-
ing from her records.
                              III
   What remains is whether the out-of-court statements
Longoni conveyed were testimonial. As earlier explained,
that question is independent of everything said above: To
implicate the Confrontation Clause, a statement must be
hearsay (“for the truth”) and it must be testimonial—and
those two issues are separate from each other. See supra,
at 3. The latter, this Court has stated, focuses on the “pri-
mary purpose” of the statement, and in particular on how it
relates to a future criminal proceeding. See ibid. (noting
varied formulations of the standard).5 A court must there-
fore identify the out-of-court statement introduced, and
must determine, given all the “relevant circumstances,” the
principal reason it was made. Bryant, 

.
   But that issue is not now fit for our resolution. The ques-
tion presented in Smith’s petition for certiorari did not ask
whether Rast’s out-of-court statements were testimonial.
See supra, at 11, n. 3 (quoting Pet. for Cert. i). Instead, it
took as a given that they were. See id., at i. That presen-
tation reflected the Arizona Court of Appeals’ opinion. As
described earlier, that court relied on the “not for the truth”
——————
  5 Given that focus, the mine-run of materials on which most expert wit-

nesses rely in forming opinions—including books and journals, surveys,
and economic or scientific studies—will raise no serious confrontation is-
sues. See Brief for United States as Amicus Curiae 13–17 (giving exam-
ples of classic expert-basis evidence). That is because the preparation of
those materials generally lacks any “evidentiary purpose.” Melendez-
Diaz, 

.
20                    SMITH v. ARIZONA

                      Opinion of the Court

rationale we have just rejected. See supra, at 10. It did not
decide whether Rast’s statements were testimonial. Nor, to
our knowledge, did the trial court ever take a stance on that
issue. Because “we are a court of review, not of first view,”
we will not be the pioneer court to decide the matter. Cutter
v. Wilkinson, 

 (2005). And indeed,
we are not sure if there remains a matter to decide. Smith
argues that the State has forfeited the argument: Arizona,
he says, “gave no hint in the proceedings below that it be-
lieved Rast’s statements were anything but testimonial.”
Reply Brief 3. The State denies that assertion, pointing to
a passage about Williams in its lower court briefing. See
Brief for Arizona 39, n. 14. The dispute is best addressed
by a state court. So we return the testimonial issue, includ-
ing the threshold forfeiture matter, to the Arizona Court of
Appeals.
   But we offer a few thoughts, based on the arguments
made here, about the questions the state court might use-
fully address if the testimonial issue remains live. First,
the court will need to consider exactly which of Rast’s state-
ments are at issue. In this Court, the parties disputed
whether Longoni was reciting from Rast’s notes alone, or
from both her notes and final report. See supra, at 8–9 (de-
scribing those documents). In Arizona’s view, everything
Longoni testified to came from Rast’s notes; although he at
times used the word “report,” a close comparison of the doc-
uments and his testimony reveals (the State says) that he
meant only the notes. See Brief for Arizona 39–40; Tr. of
Oral Arg. 69–72; see also App. to Pet. for Cert. 39a–40a,
48a. Smith disagrees, taking Longoni’s references to the
“report,” as well as the notes, at face value. According to
Smith, Longoni “relied on both” documents and in fact
“treated them as a unit,” with the notes “attached” to the
report as “essentially an appendix.” Reply Brief 4; Tr. of
Oral Arg. 25, 98. Resolving that dispute might, or then
again might not, affect the court’s ultimate disposition of
                  Cite as: 

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                      Opinion of the Court

Smith’s Confrontation Clause claim. We note only that be-
fore the court can decide the primary purpose of the out-of-
court statements introduced at Smith’s trial, it needs to de-
termine exactly what those statements were.
   In then addressing the statements’ primary purpose—
why Rast created the report or notes—the court should con-
sider the range of recordkeeping activities that lab analysts
engage in. See generally supra, at 3 (describing formula-
tions of the testimonial inquiry). After all, some records of
lab analysts will not have an evidentiary purpose. The
United States as amicus curiae notes, for example, that lab
records may come into being primarily to comply with la-
boratory accreditation requirements or to facilitate internal
review and quality control. See Tr. of Oral Arg. 51. Or some
analysts’ notes may be written simply as reminders to self.
See id., at 20, 52. In those cases, the record would not count
as testimonial. To do so, the document’s primary purpose
must have “a focus on court.” Id., at 52. And again, the
state court on remand should make that assessment as to
each record whose substance Longoni conveyed.
                              IV
  Our holding today follows from all this Court has held
about the Confrontation Clause’s application to forensic ev-
idence. A State may not introduce the testimonial out-of-
court statements of a forensic analyst at trial, unless she is
unavailable and the defendant has had a prior chance to
cross-examine her. See Crawford, 

; Melen-
dez-Diaz, 

. Neither may the State intro-
duce those statements through a surrogate analyst who did
not participate in their creation. See Bullcoming, 

. And nothing changes if the surrogate—as in this
case—presents the out-of-court statements as the basis for
his expert opinion. Those statements, as we have ex-
plained, come into evidence for their truth—because only if
22                    SMITH v. ARIZONA

                      Opinion of the Court

true can they provide a reason to credit the substitute ex-
pert. So a defendant has the right to cross-examine the per-
son who made them.
  That means Arizona does not escape the Confrontation
Clause just because Rast’s records came in to explain the
basis of Longoni’s opinion. The Arizona Court of Appeals
thought otherwise, and so we vacate its judgment. To ad-
dress the additional issue of whether Rast’s records were
testimonial (including whether that issue was forfeited), we
remand the case for further proceedings not inconsistent
with this opinion.
                                             It is so ordered.
                   Cite as: 

 (2024)              1

                  THOMAS, J., concurring in part

SUPREME COURT OF THE UNITED STATES
                           _________________

                            No. 22–899
                           _________________


        JASON SMITH, PETITIONER v. ARIZONA
   ON WRIT OF CERTIORARI TO THE COURT OF APPEALS OF
                 ARIZONA, DIVISION ONE
                          [June 21, 2024]

   JUSTICE THOMAS, concurring in part.
   I join the Court in all but Part III of its opinion. The Sixth
Amendment’s Confrontation Clause provides: “In all crimi-
nal prosecutions, the accused shall enjoy the right . . . to be
confronted with the witnesses against him.” This Clause
bars the admission of an absent witness’s testimonial state-
ments for their truth, unless the witness is unavailable
and the defendant previously had an opportunity to cross-
examine that witness. See Crawford v. Washington, 

, 50–56, 60, n. 9 (2004). Today, the Court correctly
concludes that “[w]hen an expert conveys an absent ana-
lyst’s statements in support of his opinion, and the state-
ments provide that support only if true, then the state-
ments come into evidence for their truth.” Ante, at 2; see
also Williams v. Illinois, 

 (2012) (THOMAS,
J., concurring in judgment). But, a question remains
whether that analyst’s statements were testimonial. I
agree with the Court that, because the courts below did not
consider this question, we should remand for the Arizona
Court of Appeals to answer it in the first instance. Ante, at
19–20. But, I disagree with the Court’s suggestion that the
Arizona Court of Appeals should answer that question by
looking to each statement’s “primary purpose.” Ante, at 20–
21.
   I continue to adhere to my view that “the Confrontation
2                       SMITH v. ARIZONA

                    THOMAS, J., concurring in part

Clause is implicated by extrajudicial statements only inso-
far as they are contained in formalized testimonial materi-
als, such as affidavits, depositions, prior testimony, or con-
fessions.” * White v. Illinois, 

 (1992)
(THOMAS, J., concurring in part and concurring in judg-
ment); see also Ohio v. Clark, 

, 254–255 (2015)
(THOMAS, J., concurring in judgment); Williams, 567 U. S.,
at 110–111 (opinion of THOMAS, J.); Michigan v. Bryant, 

 (2011) (THOMAS, J., concurring in judgment);
Melendez-Diaz v. Massachusetts, 

 (2009)
(THOMAS, J., concurring); Giles v. California, 

,
377–378 (2008) (THOMAS, J., concurring); Davis v. Washing-
ton, 

 (2006) (opinion of THOMAS, J.); Lilly
v. Virginia, 

 (1999) (THOMAS, J., concur-
ring in part and concurring in judgment). The Confronta-
tion Clause guarantees a criminal defendant “the right . . .
to be confronted with the witnesses against him.” Amdt. 6.
As I have previously explained, “[w]itnesses . . . are those
who bear testimony. And testimony is a solemn declaration
or affirmation made for the purpose of establishing or prov-
ing some fact.” Davis, 

 (opinion of THOMAS,
J.) (citation, internal quotation marks, and alterations
omitted). This understanding is grounded in “[t]he history
surrounding the right to confrontation,” which “was devel-
oped to target particular practices that occurred under the
English bail and committal statutes passed during the
reign of Queen Mary, namely, the civil-law mode of criminal
procedure, and particularly its use of ex parte examinations
as evidence against the accused.” 

 (internal quo-
tation marks omitted). Rather than attempt to divine a
statement’s “primary purpose,” I would look for whether the

——————
 *The Confrontation Clause “also reaches the use of technically infor-
mal statements when used to evade the formalized process.” Davis v.
Washington, 

 (2006) (THOMAS, J., concurring in judg-
ment in part and dissenting in part).
                 Cite as: 

 (2024)           3

                 THOMAS, J., concurring in part

statement is “similar in solemnity to the Marian examina-
tion practices that the Confrontation Clause was designed
to prevent.” Williams, 

 (opinion of THOMAS,
J.). In my view, the Arizona Court of Appeals should con-
sider on remand whether the statements at issue have the
requisite formality and solemnity to qualify as testimonial.
If they do not, the Confrontation Clause poses no barrier to
their admission.
                  Cite as: 

 (2024)            1

                 GORSUCH, J., concurring in part

SUPREME COURT OF THE UNITED STATES
                          _________________

                           No. 22–899
                          _________________


       JASON SMITH, PETITIONER v. ARIZONA
   ON WRIT OF CERTIORARI TO THE COURT OF APPEALS OF
                 ARIZONA, DIVISION ONE
                         [June 21, 2024]

   JUSTICE GORSUCH, concurring in part.
   I am pleased to join the Court’s opinion holding that,
when an expert presents another’s statements as the “ba-
sis” for his own opinion, he is offering those statements for
their truth. See Parts I, II, and IV, ante.
   I cannot join, however, the Court’s discussion in Part III
about when an absent analyst’s statement might qualify as
“testimonial.” See ante, at 19–21. As the Court says, “that
issue is not now fit for our resolution.” Ante, at 19. It was
not part of the question presented for our review, nor was
it the focus of the decision below. Ante, at 19–20. In fact,
the State devoted so little attention to the “testimonial” is-
sue in the Arizona courts that any argument it might make
on the subject on remand may be forfeited. Ante, at 20.
Further, the Court’s thoughts on the subject are in no way
necessary to the resolution of today’s dispute. What makes
a statement testimonial, the Court notes, is an entirely
“separate” issue. Ante, at 19.
   Nor am I entirely sure about the guidance found in Part
III. The Sixth Amendment protects the accused’s “right . . .
to be confronted with the witnesses against him.” As the
Court sees it, whether a statement being offered for its
truth and tendency to inculpate a defendant triggers that
right depends “on the ‘primary purpose’ of the statement,
and in particular on how it relates to a future criminal pro-
ceeding.” Ante, at 19. I cannot help but wonder whether
2                     SMITH v. ARIZONA

                 GORSUCH, J., concurring in part

that is correct.
    Just consider a few other possibilities. In protecting the
right to confront “witnesses,” perhaps the Sixth Amend-
ment reaches any “person who gives or furnishes evidence.”
United States v. Hubbell, 

, 49–50 (2000)
(THOMAS, J., concurring) (discussing founding-era meaning
of the word “witness” in the Fifth Amendment); see also 

. Or perhaps the Amendment reaches all “those
who ‘bear testimony.’ ” Crawford v. Washington, 

 (2004) (quoting 2 N. Webster, An American Diction-
ary of the English Language (1828)). Perhaps, too, a state-
ment “bears testimony” so long as it “explicitly or implicitly
. . . relate[s] a factual assertion or disclose[s] information.”
Doe v. United States, 

 (1988) (discussing
what makes a statement “testimonial” for purposes of the
Fifth Amendment); see also 2 Webster, An American Dic-
tionary (observing near the founding that “testimony” could
mean “evidence” and “proof of some fact” as well as a “sol-
emn declaration or affirmation” made to “establis[h] or
prov[e] some fact”). To my mind, all these questions (and
maybe others too) warrant careful exploration in a case that
presents them and, without more assurance, I worry that
the Court’s proposed “primary purpose” test may be a limi-
tation of our own creation on the confrontation right.
    I am concerned, as well, about the confusion a “primary
purpose” test may engender. Does it focus, for example, on
the purposes an objective observer would assign to a chal-
lenged statement, see ante, at 3 (referencing the “ ‘objective
witness’ ”), the declarant’s purposes in making it, see ante,
at 21 (asking “why Rast created the report or notes”), the
government’s purposes in “ ‘procur[ing]’ ” it, see ante, at 3,
or maybe still some other point of reference? Even after we
figure out a statement’s purposes, how do we pick the pri-
mary one out of the several a statement might serve? Or
determine in exactly what way that purpose must “relat[e]
to a future criminal proceeding”? Ante, at 19. And if we fail
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                 GORSUCH, J., concurring in part

to find some foothold in text and historical practice for re-
solving these questions, how can judges answer them with-
out resort to their own notions of what would be best?
  Some time ago, Chief Justice Marshall charged the judi-
ciary with “be[ing] watchful of every inroad” on the ac-
cused’s right to be confronted with the witnesses against
him. United States v. Burr, 

 (No. 14,694)
(CC Va. 1807). With that cautionary note in mind, I re-
spectfully concur in all but Part III of the Court’s opinion.
                 Cite as: 

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                ALITO, J., concurring in judgment

SUPREME COURT OF THE UNITED STATES
                          _________________

                          No. 22–899
                          _________________


       JASON SMITH, PETITIONER v. ARIZONA
  ON WRIT OF CERTIORARI TO THE COURT OF APPEALS OF
                ARIZONA, DIVISION ONE
                        [June 21, 2024]

  JUSTICE ALITO, with whom the CHIEF JUSTICE joins, con-
curring in the judgment.
  Today, the Court inflicts a needless, unwarranted, and
crippling wound on modern evidence law. There was a time
when expert witnesses were required to express their opin-
ions as responses to hypothetical questions. But eventu-
ally, this highly artificial, awkward, confusing, and abuse-
laden form of testimony earned virtually unanimous con-
demnation. More than a century ago, judges, evidence
scholars, and legal reform associations began to recommend
that courts abandon the required use of hypotheticals, and
more than 50 years ago, the Federal Rules of Evidence did
so. Now, however, the Court proclaims that a prosecution
expert will frequently violate the Confrontation Clause
when he testifies in strict compliance with the Federal
Rules of Evidence and similar modern state rules. Instead,
the Court suggests that such experts revert to the form that
was buried a half-century ago. Ante, at 18. There is no good
reason for this radical change.
                              I
  To explain why I think the Court has gone far astray, I
begin with a brief look at the history of expert testimony—
and particularly, why the hypothetical-question require-
ment was replaced by the (superior) mode of testimony al-
lowed by the Federal Rules of Evidence.
2                     SMITH v. ARIZONA

                ALITO, J., concurring in judgment

                              A
   Expert testimony presents a challenge for a legal system
like ours that restricts a fact-finder’s ability to consider
hearsay. This is so because an expert’s opinion very often
is based on facts that are not proved in court. As a modern
treatise puts it, the value of experts lies in their ability to
“brin[g] to bear a body of knowledge largely extraneous to
the facts of the particular case.” D. Kaye, D. Bernstein, A.
Ferguson, M. Wittlin, & J. Mnookin, The New Wigmore: Ex-
pert Evidence §1.2.1, p. 4 (3d ed. 2021) (Kaye). Wigmore
made the same point when he wrote that “[n]o one profes-
sional man can know from personal observation more than
a minute fraction of the data which he must every day treat
as working truths.” 1 J. Wigmore, Evidence §665(3), p. 762
(1904) (Wigmore). Instead, experts routinely “rel[y] on the
reported data of fellow-scientists, learned by perusing their
reports in books and journals.” Id., at 762–763 (emphasis
deleted); see also Kaye §4.1, at 165 (“[P]art of an expert’s
very expertise inevitably derive[s] from hearsay”).
   Despite this problem, courts in Great Britain and this
country long ago recognized the value of expert testimony
and concluded that they “must . . . accept this kind of
knowledge from scientific men,” even if it meant allowing
testimony based on facts of which the expert did not have
firsthand knowledge. See 1 Wigmore 763; 1 S. Greenleaf,
Evidence §430(l), p. 529 (rev. 16th ed. 1899) (“It would be
absurd to deny judicial standing to such knowledge, be-
cause all scientific data must be handed down from genera-
tion to generation by hearsay, and each student can hope to
test only a trifling fraction of scientific truth by personal
experience”); Slocovich v. Orient Mut. Ins. Co., 

, 

 (1888) (“An expert is qualified to give
evidence as to things which he has never seen. He may base
an opinion upon facts proved by other witnesses, or upon
facts assumed and embraced within the case”).
   Recognizing this reality, a court in the late-18th century
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                ALITO, J., concurring in judgment

admitted expert testimony about the seaworthiness of a
ship based on a survey conducted when the expert was not
present. Thornton v. Royal Exchange Assurance Co., Peake
37, 38, 170 Eng. Rep. 70, 71 (N. P. 1790). Similarly, an
early-19th century decision allowed ship surveyors to tes-
tify to the seaworthiness of a vessel they had never seen.
Beckwith v. Sydebotham, 1 Camp. 116, 170 Eng. Rep. 897
(N. P. 1807). The opposing party objected that the experts
did not know the underlying facts to be true, but the court
admitted their opinions because the experts’ technical
knowledge could assist the jury. Ibid. The fact that “the
truth of the facts stated to them was not certainly known”
went to the weight of the testimony, not its admissibility.
Ibid.
   Throughout the 19th and into the 20th century, experts
generally testified in the form of an opinion in response to
a hypothetical question. An attorney would ask an expert
to assume that certain facts were true and would then
query whether a particular conclusion could conceivably fol-
low. See 3 S. Saltzburg, M. Martin, D. Capra, & J. Berch,
Federal Rules of Evidence Manual §703.02[1] (13th ed.
2023).
   This procedure was highly artificial because it bore little
resemblance to the way in which experts actually form opin-
ions. And the procedure surely did not conform to the way
lay jurors think and speak.
   The procedure’s aim was to prevent a jury from jumping
to the conclusion that the facts packed into the hypothetical
were true, but it is questionable whether the practice
achieved that objective. For instance, here is the question
that defense counsel asked a psychiatric witness in Charles
Guiteau’s trial for murdering President Garfield:
    “Q. . . . Assume it to be a fact that there was a strong
    hereditary taint of insanity in the blood of the prisoner
    at the bar; also that at about the age of thirty-five years
4                    SMITH v. ARIZONA

               ALITO, J., concurring in judgment

    his mind was so much deranged that he was a fit sub-
    ject to be sent to an insane asylum; also that at differ-
    ent times from that date during the next succeeding
    five years he manifested such decided symptoms of in-
    sanity, without stimulation, that many different per-
    sons conversing with him and observing his conduct be-
    lieved him to be insane; also that during the month of
    June, 1881, at about the expiration of said term of five
    years, he honestly became dominated by the idea that
    he was inspired of God to remove by death the Presi-
    dent of the United States; also that he acted upon what
    he believed to be such inspiration, and what he believed
    to be in accordance with the Divine will, in preparation
    for and in the accomplishment of such purpose; also
    that he committed the act of shooting the President un-
    der what he believed to be a Divine command which he
    was not at liberty to disobey, and which belief
    amounted to a conviction that controlled his conscience
    and over-powered his will as to that act, so that he
    could not resist the mental pressure upon him; also
    that immediately after the shooting he appeared calm
    and as one relieved by the performance of a great duty;
    also that there was no other adequate motive for the
    act than the conviction that he was executing the Di-
    vine will for the good of his country—assuming all
    these propositions to be true, state whether in your
    opinion the prisoner was sane or insane at the time of
    shooting President Garfield?
    “A. Assuming those to be true, I should say the pris-
    oner was insane.” C. Rosenberg, The Trial of the As-
    sassin Guiteau 144–145 (1968) (Rosenberg).
How likely is it that a jury hearing a question like that
would keep in mind that all the facts loaded into the ques-
tion were merely hypothetical and not necessarily sup-
ported by the evidence in the case?
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                ALITO, J., concurring in judgment

   The Guiteau example illustrates many other problems
with hypothetical questioning. For one, hypothetical ques-
tions were “difficult for the attorneys to frame, for the court
to rule on, and for the jury to understand.” M. Ladd, Expert
Testimony, 

, 425 (1952) (Ladd). Like
the question above, the hypotheticals were often “so built
up and contrived” that they were impossible for either the
jury or the expert to follow. 1 J. Wigmore, Evidence 1095
(2d ed. 1923) (1 Wigmore 2d); accord, Ladd 427. One case
involved a hypothetical that extended over “eighty-three
pages of typewritten transcript, and an objection involved
in fourteen pages more of the record.” Treadwell v. Nickel,

, 

 (1924). Such questions re-
quired an expert to have the extraordinary ability “to com-
prehend in one mental operation the entirety of what has
been asked so as to give any answer.” Ladd 427; see, e.g.,
Editorials, The Hypothetical Question Again, 24 J. Crim. L.
& C. 517, 517–519 (1933). And juries surely found following
lengthy hypotheticals even more mystifying.
   For another, lawyers often used hypotheticals as a pre-
view of their closing arguments. See, e.g., Rosenberg 144
(“Assume . . . that he committed the act of shooting the
President under what he believed to be a Divine command
which he was not at liberty to disobey . . . so that he could
not resist the mental pressure upon him”); see also S. Gross,
Expert Evidence, 

, 1162 (Gross);
Wigmore 2d §686, at 1095; Ladd 246. In doing so, they
sometimes sneaked in “irrelevant” information, Gross 1162,
and excluded necessary details, W. White, Insanity and the
Criminal Law 86 (1923) (White) (describing the hypothet-
ical question as “eliminat[ing] from consideration every hu-
man element which every common-sense man takes into
consideration when he formulates an opinion”). One medi-
cal expert declared that he “ha[d] never known a hypothet-
ical question, in a trial involving the mental condition of the
defendant, which in [his] opinion offered a fair presentation
6                     SMITH v. ARIZONA

                ALITO, J., concurring in judgment

of the case.” Ibid. As a result, experts either provided an-
swers that were entirely disconnected from “the actual
case,” 1 Wigmore 2d §686, at 1095, or else they ignored the
hypothetical altogether, 

.
   Because opposing counsel often disagreed for strategic
reasons about which facts should be included in a hypothet-
ical, constructing a hypothetical that the judge would per-
mit was often a tricky and contentious business. If counsel
did not include enough facts to satisfy opposing counsel, the
hypothetical would be met with an objection, and its suffi-
ciency would provide grist for an appeal. F. Rossi, Expert
Witnesses 114 (1991). The threat of dragging out litigation
led counsel to make their hypotheticals even longer and
more confusing. 

   By the early-20th century, this form of testimony was
scorned. In the second edition of his treatise, issued in
1923, Wigmore proclaimed the hypothetical question “that
feature which does most to disgust men of science with the
law of Evidence.” 1 Wigmore 2d §686, at 1094. Around the
same time, Judge Learned Hand labeled hypotheticals “the
most horific and grotesque wen upon the fair face of justice.”
Address of L. Hand: The Deficiencies of Trials to Reach the
Heart of the Matter, in Lectures on Legal Topics, 1921–
1922, p. 104 (1926). Professor Charles T. McCormick de-
scribed hypotheticals as “an obstruction to the administra-
tion of justice.” Some Observations Upon the Opinion Rule
and Expert Testimony, 23 Texas L. Rev. 109, 128 (1945)
(McCormick). Experts shared these concerns; one lamented
that lawyers’ use of hypothetical questions was often “so un-
fair and confusing and degrading that it does not clarify the
issue nor help achieve justice.” H. Hulbert, Psychiatric Tes-
timony in Probate Proceedings, 2 Law & Contemp. Prob.
448, 455 (1935). Eventually, the use of hypothetical ques-
tions was “nearly universally recognized as a practical dis-
aster” by lawyers, judges, and witnesses alike. Kaye §4.4,
at 189.
                     Cite as: 

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                   ALITO, J., concurring in judgment

   This state of affairs sparked efforts to eliminate hypo-
thetical questions as a requirement. See, e.g., 1 Wigmore
2d §686, at 1094 (“The Hypothetical Question must go, as a
requirement. Its abuses have become so obstructive and
nauseous that no remedy short of extirpation will suffice”
(emphasis deleted)). Change began first in the courts,
which allowed experts to sit through trial and then provide
their opinion “ ‘upon the evidence.’ ” 3 C. Chamberlayne,
Modern Law of Evidence §§2482, 2483, pp. 3343–3346
(1912).
   More formalized rule changes soon followed. In 1937, the
Commissioners on Uniform State Laws incorporated a pro-
vision in their Model Expert Testimony Act that permitted
experts to give their opinions without preliminarily disclos-
ing their underlying facts or data. Advisory Committee’s
Notes to Fed. Rule Evid. 705. In quick succession, both the
Model Code of Evidence, issued by the American Law Insti-
tute in 1942, and the Uniform Rules of Evidence, approved
by the American Bar Association in 1953, recommended
abandonment of hypothetical questions. See ALI, Model
Code of Evidence Rule 409, Comment b, p. 211 (the hypo-
thetical question “has been so grossly abused as to be al-
most a scandal”); Uniform Rules of Evidence, Rule 58, Com-
ment, p. 194 (“This rule does away with the necessity of
following the practice (grossly abused) of using the hypo-
thetical question”). In 1972, the Federal Rules of Evidence
followed suit with Rules 703 and 705, and many States
made similar changes.
                             B
   What replaced hypotheticals was the procedure exempli-
fied by the Federal Rules of Evidence.1 Rule 703 provides
——————
  1 I refer to the Federal Rules to illustrate the consequences of the

Court’s opinion. The witness in this case testified in an Arizona state
court, and his testimony was therefore governed by the relevant state
rules, which are virtually identical to the Federal Rules. Of course, the
8                         SMITH v. ARIZONA

                   ALITO, J., concurring in judgment

that an expert’s opinion may be based on “facts or data in
the case that the expert has been made aware of or person-
ally observed.” And “[u]nless the court orders otherwise,”
Rule 705 permits the expert to “state an opinion—and give
the reasons for it—without first testifying to the underlying
facts or data.”
   These facts or data need not be “admissible” in evidence,
and they are not admitted for the truth of what they assert.
Fed. Rule Evid. 703. Instead, these facts or data may, un-
der some circumstances, be disclosed to the jury for a lim-
ited purpose: to assist the jurors in judging the weight that
should be given to the expert’s opinion. Ibid. However, this
is not allowed unless the court determines that “their pro-
bative value in helping the jury evaluate the [expert’s] opin-
ion substantially outweighs their prejudicial effect.” Ibid.
And to prevent the jury from improperly relying on basis
testimony for the truth of the matters it asserts, a judge
must instruct the jury upon request to consider such evi-
dence only to assess the quality of the expert’s testimony
(i.e., to determine whether an expert’s statements are reli-
able). See Advisory Committee’s Notes on Fed. Rule Evid.
703, 28 U. S. C. App., p. 393; Fed. Rule Evid. 105 (“If the
court admits evidence that is admissible . . . for a [limited]
purpose—but not . . . for another purpose—the court, on
timely request, must restrict the evidence to its proper
scope and instruct the jury accordingly”).
   This procedure is sensitive to the risk of jurors’ mistak-
enly treating an expert’s basis testimony as evidence of the
truth of the facts of data upon which the expert relied. The
Rules provide important safeguards against this danger,
such as the stringent “probative value versus potential prej-
udice” test and the requirement that a limiting instruction

——————
Arizona courts are free to interpret those rules as they see fit, and I do
not address the question whether the witness’s testimony was proper un-
der Arizona law.
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                ALITO, J., concurring in judgment

be given upon request. Plus, of course, an expert’s lack of
personal knowledge of the “facts or data” that are called to
his attention can be brought out in cross examination and
stressed in a closing argument.
   This modern system is more honest because it reflects
how experts actually form opinions. See Advisory Commit-
tee’s Notes on Fed. Rule Evid. 703, at 393 (describing the
Rule as “designed to . . . bring the judicial practice in line
with the practice of the experts themselves when not in
court”). It is simpler and less likely to confuse. And it
avoids many of the pitfalls of the old procedure. It may not
be perfect—and evidence scholars have proposed a variety
of reforms—but it is unquestionably better than the old re-
gime it replaced.
                               II
   In light of the woeful history of expert testimony by hy-
potheticals, why has the Court disinterred that procedural
monstrosity? The Court reasons that “[i]f an expert for the
prosecution conveys an out-of-court statement in support of
his opinion, and the statement supports that opinion only if
true, then the statement has been offered for the truth of
what it asserts.” Ante, at 14. Or put differently, “the truth
of the basis testimony is what makes it useful to the prose-
cutor; that is what supplies the predicate for—and thus
gives value to—the state expert’s opinion.” Ibid. In other
words, the Court seems to think that all basis testimony is
necessarily offered for its truth.
   This is just plain wrong. What makes basis evidence
“useful” is the assistance it gives the fact-finder in judging
the weight that should be given to the expert’s opinion. See
Advisory Committee’s Notes on Rule 703 (basis testimony
may be brought before a jury to help it “evaluate the . . .
opinion”). And a trial judge must, upon request, instruct
the jury to consider it only for that purpose. If a judge rules
10                     SMITH v. ARIZONA

                 ALITO, J., concurring in judgment

that basis evidence is not admitted for its truth and so in-
structs the jury, where does the Court discern a Confronta-
tion Clause problem?
   The only possible explanation is that the Court believes
that juries are incapable of following such an instruction,
but that conclusion is inconsistent with commonplace trial
practice and with a whole string of our decisions. It is a
routine matter for trial judges to instruct juries that evi-
dence is admitted for only a limited purpose. This Court
acknowledged as much in United States v. Abel, 

 (1984), when it noted that “there is no rule of evidence
which provides that testimony admissible for one purpose
and inadmissible for another purpose is thereby rendered
inadmissible; quite the contrary is the case.” 

. In
such instances, courts use limiting instructions. See Fed.
Rule Evid. 105; 1 R. Mosteller et al., McCormick on Evi-
dence §59, pp. 481–483 (8th ed. 2020).
   And this Court has repeatedly upheld that practice—
even in “situations with potentially life-and-death stakes
for defendants” and even with respect to statements that
are “some of the most compelling evidence of guilt available
to a jury,” Samia v. United States, 

, 646–647
(2023). These decisions “credi[t] jurors by refusing to as-
sume that they are either ‘too ignorant to comprehend, or
were too unmindful of their duty to respect, instructions’ of
the court.” 

. Indeed, we have described the as-
sumption “ ‘that juries will follow the instructions given
them by the trial judge’ ” as “ ‘crucial’ ” to “the system of trial
by jury.” Marshall v. Lonberger, 

(1983) (quoting Parker v. Randolph, 

(1979)); accord, Francis v. Franklin, 

, 324–325,
n. 9 (1985).
   A brief survey of prior decisions shows how firmly this
Court has adhered to that practice. In Harris v. New York,

 (1971), the Court held that statements ob-
tained from a defendant in violation of Miranda v. Arizona,
                  Cite as: 

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                ALITO, J., concurring in judgment

 (1966), could be introduced to impeach that
defendant’s credibility, so long as the jury was instructed
not to consider them as evidence of his guilt. In Walder v.
United States, 

 (1954), the Court affirmed the
use of evidence obtained in violation of the Fourth Amend-
ment for impeachment when the trial court had “carefully
charged the jury” that it could not be considered evidence of
guilt. 

. In Spencer v. Texas, 

 (1967),
the Court upheld the admission of evidence of the defend-
ant’s prior criminal convictions for the purpose of sentence
enhancement, provided that the jury was instructed that
this evidence could not be used in determining guilt.       In
Watkins v. Sowders, 

 (1981), the Court pre-
sumed that a jury could properly evaluate an eyewitness
identification “under the instructions of the trial judge.”

. And in Tennessee v. Street, 

 (1985),
the Court approved the admission of an accomplice’s in-
criminating confession given the “pointe[d] instruct[ions]
[of] the trial court ‘not to consider the truthfulness of [the
confession] in any way whatsoever.’ ” 

 at 414–415.
   Most recently in Samia, we held that a limiting instruc-
tion was sufficient to defeat a Confrontation Clause claim.
In that homicide case, evidence showed that Samia had
traveled with his codefendant Stillwell to the Philippines to
commit a murder for hire. Samia, 

. The
trial court admitted Stillwell’s confession, which, as re-
dacted, stated that he was in a van with some “other per-
son ” when that person shot the victim, but the court told
the jury that the confession could be considered only for the
purpose of determining whether Stillwell himself was
guilty. 

. Samia argued that admitting the con-
fession even with the limiting instruction would inevitably
prejudice him because “other evidence and statements at
trial enabled the jury to immediately infer that the ‘other
person’ described in the confession was Samia him-
self.” 

 Nevertheless, we presumed that the jury was
12                    SMITH v. ARIZONA

                ALITO, J., concurring in judgment

able to follow the limiting instruction, and we therefore af-
firmed Samia’s murder conviction.
   Our cases have recognized only one situation in which a
limiting instruction is insufficient: where a defendant is di-
rectly incriminated by the extrajudicial statements of a
non-testifying codefendant. Bruton v. United States, 

 (1968). We have declined to extend that excep-
tion, see Samia, 

, and the evidence in ques-
tion in Bruton cases is worlds away from an expert’s basis
testimony. If the Court thinks otherwise, it needs to ex-
plain why basis testimony falls into the Bruton category
and creates a greater risk of juror confusion than all the
other situations in which the Court has assumed that jurors
are capable of following limiting instructions.
                              III
   The Court’s assault on modern evidence law is not only
wrongheaded; it is totally unnecessary. Today’s decision
vacates the Arizona court’s judgment because the testifying
expert’s testimony was hearsay. I agree with that bottom
line, but not because of the majority’s novel theory that ba-
sis testimony is always hearsay. Rather, I would vacate
and remand because the expert’s testimony is hearsay un-
der any mainstream conception, including that of the Fed-
eral Rules of Evidence.
   To understand why, begin with the facts. A state forensic
scientist, Elizabeth Rast, tested items seized from the de-
fendant and concluded that they were marijuana and meth-
amphetamine. Rast took notes of her tests, see App. to Pet.
for Cert. 88a–126a, and she signed a report confirming the
results, see 

 at 85a–87a. At trial, Rast was unavailable,
so the prosecution called another forensic scientist,
Greggory Longoni, to provide his expert opinion about the
testing, and Longoni relied on Rast’s report in doing so.
   Under Rules 703 and 705, Longoni could have offered his
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                ALITO, J., concurring in judgment

expert opinion that, based on the information in Rast’s re-
port and notes, the items she tested contained marijuana or
methamphetamine.           In so answering, he would
acknowledge that he relied on Rast’s report and lab notes
to reach his opinion. He could have also disclosed the infor-
mation in the report, if the court found that the probative
value of that information substantially outweighed the risk
of prejudice. See Fed. Rule Evid. 703. But he could not
testify that any of the information in the report was cor-
rect—for instance, that Rast actually performed the tests
she recorded or that she did so correctly. Nor could he tes-
tify that the items she tested were the ones seized from
Smith. Longoni did not have personal knowledge of any of
these facts, and it is unclear what “reliable” scientific
“methods” could lead him to intuit their truth from Rast’s
records. Fed. Rule Evid. 702(c) (defining a permissible ex-
pert opinion).
   The strictures of the Federal Rules here track the re-
quirements of our Confrontation Clause precedents. If Lon-
goni testified to the truth of the fact that Rast actually per-
formed the tests indicated in her report and notes and that
she carried out those tests properly, he violated the Con-
frontation Clause—assuming, of course, that the notes were
“testimonial,” a question that the Court does not reach. But
he would also violate the Federal Rules, which do not allow
experts to testify to the truth of inadmissible hearsay. In
other words, except for the question whether Rast’s report
was “testimonial,” the Federal Rules and the requirements
of the Confrontation Clause are the same. This case thus
offers no occasion to blow up the Federal Rules.
   As it happens, I agree with the Court that Longoni
stepped over the line and at times testified to the truth of
the matter asserted. The prosecution asked Longoni on sev-
eral occasions to describe the tests that Rast performed or
to swear to their accuracy, and Longoni played along. He
stated as fact that Rast followed the lab’s “typical intake
14                    SMITH v. ARIZONA

                ALITO, J., concurring in judgment

process” and that she complied with the “policies and prac-
tices” of the lab. App. to Pet. for Cert. 40a–42a. He also
testified that Rast used certain “scientific method[s]” to an-
alyze the samples, such as performing certain tests or run-
ning a “blank.” Id., at 41a–42a, 46a–48a. By asserting
these facts as true, Longoni effectively entered inadmissible
hearsay into the record, thus implicating the Confrontation
Clause. The Court could have said that—and stopped
there.
                         *   *     *
  For more than a half-century, the Federal Rules of Evi-
dence and similar state rules have reasonably allowed ex-
perts to disclose the information underlying their opinion.
Because the Court places this form of testimony in consti-
tutional doubt in many cases, I concur only in the judgment.