                 FOR PUBLICATION

  UNITED STATES COURT OF APPEALS
       FOR THE NINTH CIRCUIT


ESTATE OF HENRY BARABIN;                No. 10-36142
GERALDINE BARABIN, personal
representative,                            D.C. No.
                Plaintiffs-Appellees,   2:07-cv-01454-
                                             RSL
                 v.

ASTENJOHNSON, INC.,
            Defendant-Appellant.



ESTATE OF HENRY BARABIN;                No. 11-35020
GERALDINE BARABIN, personal
representative,                            D.C. No.
                Plaintiffs-Appellees,   2:07-cv-01454-
                                             RSL
                 v.

ASTENJOHNSON, INC.,                       OPINION
                          Defendant,

                and

SCAPA DRYER FABRICS, INC.,
             Defendant-Appellant.
2           ESTATE OF BARABIN V. ASTENJOHNSON

          Appeal from the United States District Court
            for the Western District of Washington
           Robert S. Lasnik, District Judge, Presiding

                Argued and Submitted En Banc
              June 25, 2013—Seattle, Washington

                      Filed January 15, 2014

  Before: Alex Kozinski, Chief Judge, and Diarmuid F.
O’Scannlain, M. Margaret McKeown, William A. Fletcher,
Richard C. Tallman, Johnnie B. Rawlinson, Jay S. Bybee,
   Milan D. Smith, Jr., N. Randy Smith, Jacqueline H.
      Nguyen and Paul J. Watford, Circuit Judges.

                 Opinion by Judge N.R. Smith;
    Partial Concurrence and Partial Dissent by Judge Nguyen


                           SUMMARY*


                        Expert Testimony

    The en banc court vacated the district court’s judgment,
and remanded for a new trial based on its determination that
the district court failed to make findings of relevancy and
reliability before admitting into evidence certain expert
testimony, and that this error resulted in prejudice to the
defendant.


  *
    This summary constitutes no part of the opinion of the court. It has
been prepared by court staff for the convenience of the reader.
          ESTATE OF BARABIN V. ASTENJOHNSON                   3

    The en banc court held that the district court abused its
discretion by failing to make appropriate gateway
determinations under Daubert v. Merrell Dow Pharm., Inc.,
509 U.S. 579 (1993), and Federal Rule of Evidence 702,
when it admitted expert testimony at trial. The en banc court
conducted harmless error review by asking if erroneously
admitting or excluding the evidence affected the outcome of
the trial. The en banc court held that the error was prejudicial
because the erroneously admitted evidence was essential to
the defendants’ case.

    The en banc court held that a reviewing court has the
authority to make Daubert findings based on the record
established by the district court, and overruled Mukhtar v.
California State University, 299 F.3d 1053, 1066 n.12 (9th
Cir. 2002), amended by 319 F.3d 1073 (9th Cir. 2003), to the
extent that it required that Daubert findings always be made
by the district court. The en banc court concluded that the
record before the en banc court was too sparse to determine
whether the expert testimony was relevant and reliable, and
remanded for a new trial.

    Judge Nguyen, joined by Judges McKeown, W. Fletcher,
Bybee, and Watford, concurred in part and dissented in part.
Judge Nguyen concurred in Part I of the majority’s opinion,
which concluded that the district court failed to fulfill its
gatekeeping function with regard to the expert testimony at
issue, and agreed that the court was unable to determine on
the current record whether the expert testimony was
admissible. Judge Nguyen dissented with the majority’s
application of harmless error review, and would conditionally
vacate the judgment and remand with instructions to conduct
a Daubert analysis in the first instance.
4         ESTATE OF BARABIN V. ASTENJOHNSON

                        COUNSEL

Michael B. King (argued) and Emilia L. Sweeney, Carney
Badley Spellman P.S., Seattle, Washington, for Defendant-
Appellant AstenJohnson.

Mary H. Spillane and Daniel W. Ferm, Williams, Kastner &
Gibbs PLLC, Seattle Washington, for Defendant-Appellant
Scapa.

Cameron O. Carter, Brayton Purcell LLP, Portland, Oregon;
Philip A. Talmadge (argued) and Sidney Tribe,
Talmadge/Fitzpatrick PLLC, Tukwila, Washington; and Alan
R. Brayton, Gilbert L. Purcell, Lloyd F. LeRoy, James P.
Nevin, and Richard M. Grant, Brayton Purcell LLP, Novato,
California, for Plaintiffs-Appellees.


                        OPINION

N.R. SMITH, Circuit Judge:

    This case requires us to once again consider the district
court’s admission of expert testimony at trial. We review the
admission of expert testimony at trial for an abuse of
discretion. Primiano v. Cook, 598 F.3d 558, 563 (9th Cir.
2010). If the district court improperly admitted the expert
testimony, we apply harmless error review to determine
whether its decision must be reversed. United States v.
Laurienti, 611 F.3d 530, 547 (9th Cir. 2010). When we find
the erroneous admission of evidence actually prejudiced the
defendant, such that the error was not harmless, the
appropriate remedy is a new trial. See United States v. 4.85
Acres of Land, 546 F.3d 613, 620 (9th Cir. 2008). Applying
            ESTATE OF BARABIN V. ASTENJOHNSON                           5

this well-settled precedent to the facts of this case, we vacate
the judgment and remand for a new trial.1

                               FACTS

    Henry Barabin worked at Crown-Zellerbach paper mill
from 1968 until his retirement in 2001. In the mill, Crown-
Zellerbach shredded logs into chips and then exposed the
chips to corrosive chemicals and high pressure to create paper
slurry. Paper slurry is ninety-nine percent water and one
percent pulp fiber. The mill produced paper by removing
water from the paper slurry. As part of that process,
machines pulled the paper through dryers. Dryer felts held
the paper against the dryers, so that the paper would dry
properly. AstenJohnson, Inc. and Scapa Dryer Fabrics, Inc.
supplied the mill with dryer felts that contained asbestos.

    Barabin had a variety of jobs during the time he worked
at the mill. He started as a paper sorter, working in a
different building than where the dryers were located. He
then moved to the technical department, where he worked as
a pulp tester and a paper tester. On occasion, he worked at a
test station that was about twenty feet from the dryers. After
working in the technical department, he went to work on the
paper machines. Part of his job was to clean the dryers.
However, these jobs were not his only exposure to the dryer
felts; he also took pieces of dryer felt home to use in his
garden.




 1
   Because we find the erroneous admission of expert testimony warrants
a new trial, we do not address the merits of the other arguments raised by
AstenJohnson and Scapa.
6         ESTATE OF BARABIN V. ASTENJOHNSON

    In 2006, Barabin was diagnosed with pleural malignant
epithelial mesothelioma (“mesothelioma”). Mesothelioma is
a rare cancer that affects the tissue surrounding the lungs.
Alleging that this occupational exposure to asbestos from the
dryer felts caused his mesothelioma, Henry Barabin and
Geraldine Barabin, his wife, brought suit against
AstenJohnson and Scapa.

      All parties agree, and the science makes clear, that
asbestos exposure from inhaling respirable fibers can cause
mesothelioma. At trial, the parties argued over whether
exposure to the dryer felts (provided by AstenJohnson and
Scapa) substantially contributed to Barabin’s mesothelioma.
Of necessity, the case was to be a battle of the experts. Both
parties had experts who were prepared to testify in support of
their arguments.

    Two of the Barabins’ experts were Kenneth Cohen and
Dr. James Millette. Mr. Cohen had been employed in the
industrial hygiene field for several decades. He had also
taught industrial toxicology courses at a university. Dr.
Millette had been involved in asbestos related research since
1974. He published a number of articles dealing with
asbestos, including an article dealing with asbestos fiber
release from dryer felts.

    Prior to trial, AstenJohnson and Scapa filed motions in
limine to exclude Mr. Cohen and Dr. Millette as expert
witnesses. AstenJohnson argued that Mr. Cohen was not
qualified to testify as an expert and that his theory was not the
product of scientific methodology. AstenJohnson and Scapa
argued that Dr. Millette’s tests were unreliable, because his
methodology was not generally accepted in the scientific
community. They also argued that the disparity between his
             ESTATE OF BARABIN V. ASTENJOHNSON                   7

tests and the conditions at the mill was so great that his
testimony would not help the jury. The motions also sought
to exclude testimony from any expert regarding the theory
that “every asbestos fiber is causative.”

    After receiving the motions, and without a Daubert2
hearing, the district court excluded Mr. Cohen as a witness
because of his “dubious credentials and his lack of expertise
with regard to dryer felts and paper mills.” The district court
also had concerns with Dr. Millette’s testimony. Specifically,
the district court was “troubled by the marked differences
between the conditions of Dr. Millette’s tests and the actual
conditions at the [mill].” Nonetheless, the district court ruled
that Dr. Millette could testify provided the jury was informed
his tests were “performed under laboratory conditions which
are not the same as conditions at the [mill].”

     As to the “every exposure” theory, the district court found
“a strong divide among both scientists and courts” on whether
it is relevant in asbestos cases. However, “[i]n the interest of
allowing each party to try its case to the jury,” the district
court allowed the testimony.

    The Barabins then filed a motion to request a pretrial
Daubert hearing regarding Mr. Cohen. At a pretrial
conference, the district court rejected the Barabins’ request
for a Daubert hearing. Instead, it reversed its decision to
exclude Mr. Cohen’s testimony. The district court’s only
explanation for why it reversed its decision was that the
Barabins “did a much better job” in their motion “of
presenting . . . the full factual basis behind Mr. Cohen
testifying and his testimony in other cases.”

 2
     Daubert v. Merrell Dow Pharm., Inc., 509 U.S. 579 (1993).
8           ESTATE OF BARABIN V. ASTENJOHNSON

    At trial, numerous experts testified. Both Mr. Cohen and
Dr. Millette testified. Dr. Brodkin, another expert, also
testified for the Barabins. Part of Dr. Brodkin’s testimony
was about the “every exposure” theory. As each of these
experts testified, AstenJohnson and Scapa objected to their
testimony. The district court overruled the objections.

                  PROCEDURAL HISTORY

    After the Barabins presented their case at trial,
AstenJohnson and Scapa filed motions for judgment as a
matter of law. AstenJohnson and Scapa believed they were
entitled to judgment as a matter of law, because the Barabins
had failed to show that their companies had manufactured the
dryer felts to which Barabin had been exposed. In the
alternative, they argued that the Barabins had failed to
demonstrate a causal link between the dryer felts and
Barabin’s mesothelioma. The district court denied the
motions. AstenJohnson and Scapa renewed their motions
after closing arguments. The district court denied the
motions again.

    After deliberations, the jury found in favor of the
Barabins and awarded damages totaling $10,200,000. The
district court granted AstenJohnson’s and Scapa’s motions to
vacate the judgment and scheduled a reasonableness hearing.
The district court found the damages award to be reasonable,
offset the judgment by a total of $836,114.61,3 and entered



    3
    The Barabins had previously settled with a number of third parties.
Washington law requires the court to offset the judgment by the amount
of such settlements, unless the settlements were unreasonable. See Wash.
Rev. Code § 4.22.060(2).
          ESTATE OF BARABIN V. ASTENJOHNSON                   9

judgment in favor of the Barabins in the amount of
$9,373,152.12.

   Both Scapa and AstenJohnson then filed motions for a
new trial or, in the alternative, for a remittitur. One of the
grounds on which Scapa and AstenJohnson sought a new trial
was the improper admission of expert testimony. The district
court denied the motions in their entirety.

    AstenJohnson and Scapa filed timely notices of appeal.
A three-judge panel consolidated the appeals. It unanimously
held that the district court abused its discretion by failing to
make the necessary relevancy and reliability findings under
Daubert. The panel remanded for a new trial pursuant to
Mukhtar v. California State University, 299 F.3d 1053 (9th
Cir. 2002), amended by 319 F.3d 1073 (9th Cir. 2003). The
Barabins petitioned this Court to rehear the case en banc, and
a majority of non-recused active judges voted to rehear the
case.

               STANDARDS OF REVIEW

    “A district court’s evidentiary rulings should not be
reversed absent clear abuse of discretion and some
prejudice.” Grand Canyon Skywalk Dev., LLC v. ‘Sa’ Nyu
Wa Inc., 715 F.3d 1196, 1202 (9th Cir. 2013) (internal
quotations and citation omitted). However, we review de
novo the “construction or interpretation of . . . the Federal
Rules of Evidence, including whether particular evidence
falls within the scope of a given rule.” United States v.
Durham, 464 F.3d 976, 981 (9th Cir. 2006) (citations
omitted). A ruling on a motion for new trial “will be
overturned on appeal only for abuse of discretion.” Kode v.
Carlson, 596 F.3d 608, 611 (9th Cir. 2010) (citation omitted).
10          ESTATE OF BARABIN V. ASTENJOHNSON

                           DISCUSSION

                                   I.

   Rule 702 of the Federal Rules of Evidence governs
admission of expert testimony in the federal courts:

         If scientific, technical, or other specialized
         knowledge will assist the trier of fact to
         understand the evidence or to determine a fact
         in issue, a witness qualified as an expert by
         knowledge, skill, experience, training, or
         education, may testify thereto in the form of
         an opinion or otherwise, if (1) the testimony is
         based upon sufficient facts or data, (2) the
         testimony is the product of reliable principles
         and methods, and (3) the witness has applied
         the principles and methods reliably to the
         facts of the case.

Fed. R. Evid. 702 (2010).4 We have interpreted Rule 702 to
require that “[e]xpert testimony . . . be both relevant and
reliable.” United States v. Vallejo, 237 F.3d 1008, 1019 (9th
Cir. 2001). Relevancy simply requires that “[t]he evidence
. . . logically advance a material aspect of the party’s case.”
Cooper v. Brown, 510 F.3d 870, 942 (9th Cir. 2007).

    The issue here is reliability: whether an expert’s
testimony has “a reliable basis in the knowledge and
experience of the relevant discipline.” Kumho Tire Co., Ltd.
v. Carmichael, 526 U.S. 137, 149 (1999) (citation and

 4
   The trial in this case took place before the Federal Rules of Evidence
were restyled in 2011.
          ESTATE OF BARABIN V. ASTENJOHNSON                 11

alterations omitted). The “evidentiary reliability [is] based
upon scientific validity.” Daubert, 509 U.S. at 590 n.9. We
are concerned “not [with] the correctness of the expert’s
conclusions but the soundness of his methodology.”
Primiano v. Cook, 598 F.3d 558, 564 (9th Cir. 2010)
(citations and quotations omitted). The duty falls squarely
upon the district court to “act as a ‘gatekeeper’ to exclude
junk science that does not meet Federal Rule of Evidence
702’s reliability standards.” Ellis v. Costco Wholesale Corp.,
657 F.3d 970, 982 (9th Cir. 2011).

     The reliability inquiry is “a flexible one.” Kumho Tire,
526 U.S. at 150. The Supreme Court has suggested several
factors that can be used to determine the reliability of expert
testimony: “1) whether a theory or technique can be tested; 2)
whether it has been subjected to peer review and publication;
3) the known or potential error rate of the theory or
technique; and 4) whether the theory or technique enjoys
general acceptance within the relevant scientific community.”
United States v. Hankey, 203 F.3d 1160, 1167 (9th Cir. 2000)
(citing Daubert, 509 U.S. at 592–94). However, whether
these specific factors are “reasonable measures of reliability
in a particular case is a matter that the law grants the trial
judge broad latitude to determine.” Kumho Tire, 526 U.S. at
153.

    The trial judge also has broad latitude in determining the
appropriate form of the inquiry. See United States v.
Alatorre, 222 F.3d 1098, 1102 (9th Cir. 2000) (“Nowhere . . .
does the Supreme Court mandate the form that the inquiry
into relevance and reliability must take.”). While pretrial
“Daubert hearings” are commonly used, see, e.g., United
States v. Lukashov, 694 F.3d 1107, 1112 (9th Cir. 2012), they
12        ESTATE OF BARABIN V. ASTENJOHNSON

are certainly not required, United States v. Jawara, 474 F.3d
565, 582 (9th Cir. 2006).

    Nevertheless, Rule 702 “clearly contemplates some
degree of regulation of the subjects and theories about which
an expert may testify.” Daubert, 509 U.S. at 589 (emphasis
added). Applying these principles to the facts before us, we
find the district court abused its discretion by failing to make
appropriate determinations under Daubert and Federal Rule
of Evidence 702.

    The district court first excluded Mr. Cohen’s testimony
based on his “dubious credentials and lack of expertise.” The
district court’s only explanation for reversing its decision,
without a Daubert hearing or findings, was, “I think the
plaintiffs did a much better job of presenting to me the full
factual basis behind Mr. Cohen testifying and his testimony
in other cases.” Absent from the explanation is any
indication that the district court assessed, or made findings
regarding, the scientific validity or methodology of Mr.
Cohen’s proposed testimony. Therefore, the district court
failed to assume its role as gatekeeper with respect to Mr.
Cohen’s testimony.

    The district court also failed to act as gatekeeper for Dr.
Millette’s testimony.         After acknowledging various
arguments as to whether the testimony was admissible, the
district court concluded that it could be admitted, so long as
the jury was informed of the “marked differences” between
conditions of the tests and the actual conditions of the mill.
Rather than making findings of relevancy and reliability, the
district court passed its greatest concern about Dr. Millette’s
testimony to the jury to determine.
          ESTATE OF BARABIN V. ASTENJOHNSON                   13

   The district court took the same approach with respect to
expert testimony regarding the “every exposure” theory:

        There is obviously a strong divide among both
        scientists and courts on whether such expert
        testimony is relevant to asbestos-related
        cases. In the interest of allowing each party
        to try its case to the jury, the Court deems
        admissible expert testimony that every
        exposure can cause an asbestos-related
        disease.

(emphasis added). Just as the district court cannot abdicate
its role as gatekeeper, so too must it avoid delegating that role
to the jury.

    Here, the district court delegated that role by giving each
side leeway to present its expert testimony to the jury. Before
allowing the jury to hear the expert testimony, the district
court should have first determined that the “expert meets the
threshold established by Rule 702,” Primiano, 598 F.3d at
564–65; that is the entire purpose of Daubert. The district
court abused its discretion by admitting the expert testimony
without first finding it to be relevant and reliable under
Daubert.

                               II.

   When we conclude evidence has been improperly
admitted, “we consider whether the error was harmless.”
United States v. Bailey, 696 F.3d 794, 802–03 (9th Cir. 2012).
We treat the erroneous admission of expert testimony the
same as all other evidentiary errors, by subjecting it to
harmless error review. See United States v. Rahm, 993 F.2d
14          ESTATE OF BARABIN V. ASTENJOHNSON

1405, 1415 (9th Cir. 1993). We reverse “only if the error
affect[ed] a substantial right of the party.” Fed. R. Evid.
103(a). “In other words, we require a finding of prejudice.”
Obrey v. Johnson, 400 F.3d 691, 699 (9th Cir. 2005).

    “[T]he burden [is] on the beneficiary of the error either to
prove that there was no injury or to suffer a reversal of his
erroneously obtained judgment.” Id. at 700 (citation
omitted). Thus, “we begin with a presumption of prejudice.
That presumption can be rebutted by a showing that it is more
probable than not that the jury would have reached the same
verdict even if the evidence had not been admitted.” Jules
Jordan Video, Inc. v. 144942 Canada Inc., 617 F.3d 1146,
1159 (9th Cir. 2010) (citation and internal quotations
omitted).

    As the beneficiaries of the erroneously admitted evidence,
the Barabins fail to rebut the presumption of prejudice.
Indeed, they admit they cannot win without this expert
testimony.5 Prejudice is at its apex when the district court
erroneously admits evidence that is critical to the proponent’s
case. The improper admission of the expert testimony
severely prejudiced AstenJohnson and Scapa because the
Barabins’ claim depended wholly upon the erroneously
admitted evidence. Given these circumstances, there is no
doubt the error was not harmless.

 5
   At least twice during the en banc oral arguments the Barabins admitted
they did not have a case without this expert testimony. First, the Barabins’
counsel stated that, if the district judge found the expert testimony
inadmissible (specifically the testimony of Dr. Millette), the result would
be “a judgment in favor of the defendants.” Second, in response to this
Court’s suggestion that without expert testimony it was “game over” for
the Barabins, counsel stated “I think that’s right.” Our review of the
record confirms the wisdom of this concession.
             ESTATE OF BARABIN V. ASTENJOHNSON                            15

    The dissent contends that we must decide whether the
evidence would be admissible before engaging in harmless
error review. Dissent at 23. However, the dissent is reading
a non-existent step into our evidentiary-error case law.

    The dissent cites only two cases addressing the use of
harmless error review in these circumstances.6 They both
support our decision. See 4.85 Acres of Land, 546 F.3d at
620; Simpson v. Thomas, 528 F.3d 685, 691 (9th Cir. 2008).
In 4.85 Acres of Land, we found that the district court abused
its discretion by excluding all post-taking sales from
consideration without first making any findings regarding the
comparability of the excluded sales to the condemned
property. 546 F.3d at 620. Despite being asked to do so, we
refused to address on appeal whether “some of the post-
taking comparable sales would have been admissible.” Id.
Instead, we engaged in harmless error review, found that the
error was not harmless, and remanded for a new trial. Id.

    In Simpson, we found that the district court abused its
discretion when it admitted three prior convictions that were
more than ten years old without engaging in proper balancing

  6
    All of the other cases cited by the dissent do not address this issue.
They are not cases in which the district court failed to answer a threshold
question of admissibility. Instead, in each of those cases (unlike the case
at hand), we were tasked with determining whether evidence was
admissible in order to decide if the district court abused its discretion. See
Bailey, 696 F.3d at 804–05; Jules Jordan Video, Inc., 617 F.3d at
1157–59; Laurienti, 611 F.3d at 547–49; United States v. Cohen, 510 F.3d
1114, 1127 (9th Cir. 2007); Rahm, 993 F.3d at 1415–16; United States v.
Echavarria-Olarte, 904 F.2d 1391, 1398 (9th Cir. 1990). Here, our
inquiry into whether the district court abused its discretion ends with our
determination that it abdicated its gatekeeping responsibility. However,
to the extent that these cases apply, they support our decision to conduct
harmless error review after finding the district court abused its discretion.
16           ESTATE OF BARABIN V. ASTENJOHNSON

under rule 609(b) of the Federal Rules of Evidence. 528 F.3d
at 690–91. The district court identified the correct rule, but
it abused its discretion when it inverted the requirement of the
rule, failed to offer specific facts to support its conclusion,
and did not find that the probative value substantially
outweighed the prejudice. Id. at 690. We did not engage in
609(b) balancing on appeal to determine whether the prior
convictions would have been admissible. Instead, we went
straight to harmless error review, found the evidence to be
prejudicial, and remanded for a new trial. Id. at 690–91.

    As both 4.85 Acres of Land and Simpson illustrate, when
the district court abdicates its responsibility to answer a
threshold question of admissibility, we need not determine
whether the evidence would have been admissible before we
determine the district court abused its discretion and proceed
to harmless error review. In both cases we engaged in
harmless error review, as we always do, by asking if
erroneously admitting or excluding the evidence affected the
outcome of the trial.7 See 4.85 Acres of Land, 546 F.3d at


  7
    The dissent cites Hangarter v. Provident Life & Accident Ins. Co.,
373 F.3d 998 (9th Cir. 2004), to support its idea of what constitutes an
appropriate “harmless error inquiry when a district court fails to fulfill its
gatekeeping function.” Dissent at 26. This case is inapposite; the district
court in Hangarter did not fail to fulfill its gatekeeping function. We
specifically held that the district court “did not abuse its discretion in
finding [the expert’s] testimony reliable based on his knowledge and
experience” and that “the district court’s inquiry was sufficient to comply
with its gatekeeping role.” Id. at 1018.

     Instead, in Hangarter, we reviewed for harmless error the district
court’s statement that Daubert did not apply. Id. (“While the district court
erred in stating that Daubert did not apply to Caliri’s non-scientific
testimony, that error was harmless.”). It is difficult to imagine a Daubert
case that is less on point: In Hangarter, the district court said Daubert did
            ESTATE OF BARABIN V. ASTENJOHNSON                        17

620; Simpson, 528 F.3d at 691. We reject the dissent’s
attempt to insert a new step into our review of evidentiary
errors.

                                 III.

     When the district court has erroneously admitted or
excluded prejudicial evidence, we remand for a new trial.
See, e.g., B.K.B. v. Maui Police Dep’t, 276 F.3d 1091, 1109
(9th Cir. 2002). We do so even if the district court errs by
failing to answer a threshold question of admissibility. See,
e.g., 4.85 Acres of Land, 546 F.3d at 620 (excluding other
sales without determining comparability); Simpson, 528 F.3d
at 691 (admitting convictions without Federal Rule of
Evidence 609(b) balancing). We have no precedent for
treating the erroneous admission of expert testimony any
differently.

     For seventy years prior to Daubert, the dominant standard
for determining admissibility of novel scientific evidence was
the “general acceptance” test. Daubert, 509 U.S. at 585–86
(citing Frye v. United States, 293 F. 1013 (D.C. Cir. 1923)).
Under Frye, we required the proponent of novel scientific
evidence to “lay a proper foundation” by demonstrating
“general acceptance” of the evidence “in the particular field
in which it belong[ed].” United States v. Boise, 916 F.2d 497,
503 (9th Cir. 1990).

   In Daubert, the Supreme Court set “the standard for
admitting expert scientific testimony in a federal trial” by
holding that the Federal Rules of Evidence superseded the


not apply but went on to make Daubert findings. Here, the district court
said that Daubert did apply but failed to make Daubert findings.
18          ESTATE OF BARABIN V. ASTENJOHNSON

Frye test. Daubert, 509 U.S. at 582, 586–87. Daubert
continues to require that the proponent of expert testimony
lay a proper foundation, but now laying a proper foundation
means establishing relevancy and reliability rather than mere
general acceptance. Id. at 597.

    Initially, in grappling with the effects of Daubert, we
remanded two cases to district courts to conduct post-hoc
Daubert hearings. See United States v. Cordoba, 104 F.3d
225, 229 (9th Cir. 1997); United States v. Amador-Galvan,
9 F.3d 1414, 1418 (9th Cir. 1993).8 After the dust of Daubert
had settled, we held that an erroneous admission of expert
testimony, absent a showing the error was harmless, requires
a new trial. See Mukhtar, 299 F.3d at 1066–67. To the extent
Mukhtar requires anything more, it is overruled.

    AstenJohnson and Scapa contend that a reviewing court
should have the authority to make Daubert findings based on
the record established by the district court. We agree and
overrule Mukhtar to the extent that it required that Daubert
findings always be made by the district court. See Mukhtar,
299 F.3d at 1066 n.12. If the reviewing court decides the
record is sufficient to determine whether expert testimony is
relevant and reliable, it may make such findings. If it
“determines that evidence [would be inadmissible] at trial and
that the remaining, properly admitted evidence is insufficient

 8
    These are not cases in which the district court simply failed to conduct
a Daubert hearing. In Amador-Galvan, the trial took place before Daubert
had been decided, 9 F.3d at 1416, so it would have been impossible for the
district court to make Daubert findings. Cordoba dealt with an issue of
first impression: “whether our per se rule excluding the admission of
unstipulated polygraph evidence was effectively overruled by Daubert.”
104 F.3d at 227. After deciding it was, we remanded to the district court
to conduct a Daubert hearing in the first instance. Id. at 229.
          ESTATE OF BARABIN V. ASTENJOHNSON                 19

to constitute a submissible case[,]” the reviewing court may
direct entry of judgment as a matter of law. Weisgram v.
Marley Co., 528 U.S. 440, 446–47 (2000).

    Citing Weisgram, AstenJohnson and Scapa argue we
should enter judgment in this case. We decline their
invitation. In Weisgram, the Eighth Circuit found, based on
a fully developed record, that the expert testimony was not
reliable. Weisgram v. Marley Co., 169 F.3d 514, 517–18 (8th
Cir. 1999). We cannot speak to the admissibility of the
expert testimony at issue here because the record before us is
too sparse to determine whether the expert testimony is
relevant and reliable. We can only say with certainty that the
district court erred by failing to make that determination.

    The Barabins and the dissent argue that we should remand
for a post-hoc Daubert hearing. Even assuming that a limited
remand is available post-Mukhtar, see 319 F.3d at 1074, it
would not be appropriate under the circumstances here, where
the district court abused its discretion by erroneously
admitting expert testimony, and the evidence was prejudicial.
We therefore remand for a new trial.

                      CONCLUSION

    The district court failed to make findings of relevancy and
reliability before admitting into evidence the expert testimony
of Mr. Cohen and Dr. Millette and expert testimony regarding
the theory that “every asbestos fiber is causative.” The
district court’s failure to make these gateway determinations
was an abuse of discretion. The error was prejudicial because
the erroneously admitted evidence was essential to the
Barabins’ case. Due to the district court’s abdication of its
role as gatekeeper and the severe prejudice that resulted from
20         ESTATE OF BARABIN V. ASTENJOHNSON

the error, the appropriate remedy is a new trial. We vacate
the judgment and remand for a new trial.

     VACATED and REMANDED.

     The parties shall bear their own costs on appeal.



Circuit Judge NGUYEN, with whom Judges McKEOWN,
W. FLETCHER, BYBEE, and WATFORD join, concurring
in part and dissenting in part:

    I concur in Part I of the majority’s opinion, which
concludes that the district court failed to fulfill its
gatekeeping function with regard to the expert testimony at
issue. I also agree with the majority that we are unable to
determine based on the record before us whether the expert
testimony is admissible. See Maj. Op. at 19 (“We cannot
speak to the admissibility of the expert testimony at issue
here because the record before us is too sparse to determine
whether the expert testimony is relevant and reliable.”).
Further, to the extent the majority overrules Mukhtar v.
California State University, 299 F.3d 1053 (9th Cir. 2002),
amended by 319 F.3d 1073 (9th Cir. 2003), I am in accord.
There is no reason to require a new trial whenever a district
court fails to conduct a Daubert analysis, regardless of
whether on remand the district court would determine that
disputed expert testimony is relevant and reliable.

    I part ways with the majority, however, in its application
of harmless error review. The majority’s analysis is seriously
flawed because it conflates a district court’s gatekeeping error
with a district court’s erroneous determination of
           ESTATE OF BARABIN V. ASTENJOHNSON                   21

admissibility. Here, assuming inadmissibility—a question we
cannot answer at this juncture—the majority applies harmless
error review and concludes that a new trial is needed because
the “improper admission of the expert testimony severely
prejudiced [defendants].” Maj. Op. at 14 (emphasis added).
The majority thus unnecessarily burdens both the parties and
the judicial system by ordering a new trial without having a
sufficient basis to determine whether the disputed expert
testimony was admissible. Further, the majority’s approach
undercuts its effort to open the door to a limited remand
occasioned by overruling Mukhtar. Because I would
conditionally vacate the judgment and remand with
instructions to the district court to conduct a Daubert
determination in the first instance, I respectfully dissent from
Parts II and III of the majority opinion.

                                I.

    A district court must “ensure the reliability and relevancy
of expert testimony” and “make certain that an expert,
whether basing testimony upon professional studies or
personal experience, employs in the courtroom the same level
of intellectual rigor that characterizes the practice of an expert
in the relevant field.” Kumho Tire Co., Ltd. v. Carmichael,
526 U.S. 137, 152 (1999); see also Fed. R. Evid. 702. In
short, a district court serves an essential “gatekeeping”
function in evaluating proffered expert testimony. Kumho
Tire, 526 U.S. at 141.

    In this case, the district court abdicated its gatekeeping
role by failing to evaluate the relevancy and reliability of the
expert testimony at issue. Given this oversight, we must
determine whether the district court’s misstep resulted in the
admission of evidence that should have been excluded. In the
22        ESTATE OF BARABIN V. ASTENJOHNSON

past, when the record before us was sufficient to make this
determination, we have proceeded to evaluate whether the
erroneous admission or exclusion of evidence was harmless.
See, e.g., United States v. Morales, 720 F.3d 1194, 1197 (9th
Cir. 2013) (district court’s error “was harmless because the
erroneously admitted hearsay did not materially affect the
verdict”); United States v. 4.85 Acres of Land, 546 F.3d 613,
620 (9th Cir. 2008) (district court’s error was not harmless
because improper exclusion of evidence was prejudicial).
This approach makes perfect sense—once we determine that
inadmissible evidence was presented, or that admissible
evidence was excluded, we can then analyze whether the
error materially affected the verdict. See United States v.
Bailey, 696 F.3d 794, 803 (9th Cir. 2012).

     Here, however, we face a markedly different scenario. As
the majority correctly concludes, “the admissibility of the
expert testimony at issue” cannot be determined “because the
record before us is too sparse.” Maj. Op. at 19. Given this
conclusion, harmless error review is simply not possible at
the current juncture. Indeed, we cannot even say whether
there was an “error” to “materially affect the verdict.” If the
disputed expert testimony was admissible pursuant to Rule
702 and Daubert, despite the district court’s failure to fulfill
its gatekeeping function, then no harm, no foul. On the other
hand, if the testimony was inadmissible, then a harmless error
analysis would be appropriate. Thus, in light of the
outstanding question regarding the admissibility of the expert
testimony at issue, a remand to the district court for a
Daubert analysis is the proper course.
            ESTATE OF BARABIN V. ASTENJOHNSON                          23

                                   II.

    The majority goes awry in adopting an approach that
ignores this antecedent question of admissibility. In
considering the district court’s gatekeeping failure, the
majority asserts that “[w]hen we conclude evidence has been
improperly admitted, ‘we consider whether the error was
harmless.’” Maj. Op. at 13 (quoting Bailey, 696 F.3d at
802–03). Though innocuous at first glance, this remark
harbors a grave oversight: it equates an incorrect
determination of admissibility with a failure to conduct a
Daubert analysis.

     The distinction between the two is crucial. With the
former, we know whether a party was wrongfully permitted
or denied the opportunity to present certain evidence, and we
can determine whether that error was prejudicial. With the
latter, we cannot gauge prejudice unless we are able to
determine what the jury would have been permitted to hear
had the district court properly discharged its gatekeeping
duties.1

    By skipping over the question of admissibility and
heading straight for prejudice, the majority’s analysis results
in two key missteps. First, the majority dubs the Barabins
“the beneficiaries of . . . erroneously admitted evidence.” Id.

  1
    The majority cites United States v. Rahm, 993 F.2d 1405 (9th Cir.
1993), for the proposition that “[w]e treat the erroneous admission of
expert testimony the same as all other evidentiary errors, by subjecting it
to harmless error review.” Maj. Op. at 13. Rahm, however, only engaged
in harmless error review after concluding that the testimony at issue was
admissible and thus improperly excluded. See Rahm, 993 F.2d at 1416
(deeming the error not harmless where the district court “erroneously
excluded . . . proffered expert testimony . . . [that] was admissible”).
24         ESTATE OF BARABIN V. ASTENJOHNSON

at 14. But, as the majority acknowledges, we have no idea
whether the expert testimony at issue was in fact “erroneously
admitted.” On a proper Daubert analysis—a task we decline
to engage in on appeal—the testimony might indeed have
been admissible. In this circumstance, the Barabins would
merely be the beneficiaries of evidence they were entitled to
present in the first place.

    Second, in bypassing admissibility, the majority engages
in a perplexing prejudice analysis that emphasizes the fact
that the disputed expert testimony was “critical to the
proponent’s case.”2 Id. Indeed, based on its conclusion that
“the Barabins’ claim depended wholly upon the erroneously
admitted evidence,” the majority finds “no doubt the error
was not harmless.” Id. Not so. Even if the Barabins’ claim
depended on the expert testimony at issue, we have no idea
whether the testimony was “erroneously admitted,” let alone
whether any error “materially affect[ed] the verdict.”
Morales, 720 F.3d at 1197. If the expert testimony was
admissible, then the jury simply reached a verdict based on
evidence it was properly permitted to consider, despite the
district court’s error.

    The flaw in the majority’s logic is highlighted by the fact
that not a single case it cites supports the type of harmless
error analysis it applies. Rather, in each case, we engaged in
harmless error review only after we determined that evidence




   2
     It seems to me that it would be the rare case indeed where expert
testimony was not “critical to the proponent’s case.”
            ESTATE OF BARABIN V. ASTENJOHNSON                          25

had been improperly deemed admissible or inadmissible.3
Indeed, this is true of Simpson v. Thomas and United States
v. 4.85 Acres of Land—two cases specifically discussed by
the majority in support of its decision. Contrary to the
majority’s assertion, neither case involved merely a situation
where a “district court abdicate[d] its responsibility to answer
a threshold question of admissibility.” Maj. Op. at 16.
Rather, in both cases, we found actual error by the district
court in deeming evidence admissible or inadmissible before
proceeding to harmless error review. See Simpson, 528 F.3d
at 689 (“The district court erred in admitting the evidence of
Simpson’s three prior felony convictions.”); 4.85 Acres of
Land, 546 F.3d at 620 (“[T]he [district] court simply
excluded all post-taking sales based on ‘the erroneous
premise . . . that evidence of subsequent sales is never proper
for consideration in arriving at fair market value.’” (quoting


 3
   See, e.g., Bailey, 696 F.3d at 805 (not harmless error where trial court
wrongfully admitted a civil complaint); Jules Jordan Video, Inc. v. 144942
Canada, Inc., 617 F.3d 1146, 1158–59 (9th Cir. 2010) (harmless error
where district court improperly permitted counsel to read 716 requests for
admissions to the jury); United States v. Laurienti, 611 F.3d 530, 548 (9th
Cir. 2010) (harmless error where district court abused its discretion by
sustaining certain government objections to expert testimony); Simpson
v. Thomas, 528 F.3d 685, 691 (9th Cir. 2008) (not harmless error where
district court improperly admitted prior convictions); 4.85 Acres of Land,
546 F.3d at 620 (not harmless error where district court improperly
excluded post-taking sales in a condemnation action); Cohen, 510 F.3d at
1127 (not harmless error where district court wrongfully excluded expert
testimony); Obrey v. Johnson, 400 F.3d 691, 702 (9th Cir. 2005) (not
harmless error where district court abused its discretion in excluding
testimony); Rahm, 993 F.2d at 1415 (not harmless error where district
court erroneously excluded expert testimony); United States v.
Echavarria-Olarte, 904 F.2d 1391, 1398–99 (9th Cir. 1990) (harmless
error where district court improperly admitted expert testimony on drug
cartel).
26          ESTATE OF BARABIN V. ASTENJOHNSON

United States v. 1,129.75 Acres of Land, 473 F.2d 996, 999
(8th Cir. 1973)) (final alteration in original)).

    In fact, our case law suggests a notably different harmless
error inquiry when a district court fails to fulfill its
gatekeeping function. For example, in Hangarter v.
Provident Life & Accident Insurance Co., 373 F.3d 998 (9th
Cir. 2004), the district court incorrectly concluded that
Daubert was inapplicable to the non-scientific testimony of
an independent consultant. Id. at 1015–16, 1018. We found
the error harmless because “the [district] court’s probing of
[the consultant’s] knowledge and experience was sufficient
to satisfy its gatekeeping role under Daubert.” Id. at 1018.
In short, the district court’s failure to analyze the expert
testimony pursuant to Daubert was harmless because the
analysis it nonetheless conducted satisfied Daubert and the
testimony was thus correctly admitted. This was a proper
application of harmless error review—where the error
identified on appeal pertains to the gatekeeping function, the
reviewing court should consider whether the gatekeeping
error was harmless.4

    In contrast, the majority here finds a gatekeeping error,
but embarks on a prejudice inquiry that focuses on how
crucial the disputed expert testimony was to the prevailing
party’s success. In doing so, the majority effectively treats
the testimony as inadmissible, even as it professes to reserve


 4
   The majority characterizes Hangarter as “inapposite,” describing it as
a case where the district court “did not fail to fulfill its gatekeeping
function.” Maj. Op. at 16 n.7. I disagree. It is hard to imagine a more
clear gatekeeping error than a district court choosing not to analyze
proffered expert testimony under Daubert because it mistakenly found
Daubert inapplicable.
          ESTATE OF BARABIN V. ASTENJOHNSON               27

judgment on the question. The majority cannot have it both
ways.

                            III.

    I would conditionally vacate the judgment and remand to
the district court with instructions to determine whether the
disputed expert testimony was admissible pursuant to the
requirements of Rule 702 and Daubert. If the testimony is
determined to be admissible, the district court may reinstate
the verdict. If, however, the testimony is inadmissible, the
district court should ascertain whether the wrongful
admission of that expert testimony prejudiced the defendants
and, if so, order a new trial. In the former case, the system
will not be unreasonably burdened with a retrial. In either
case, the parties retain their right to appeal. This solution
makes practical and legal sense.
