      [J-92A-2019, J-92B-2019, J-92C-2019, J-92D-2019 and J-92E-2019]
                             [MO: Donohue, J.]

               IN THE SUPREME COURT OF PENNSYLVANIA
                          WESTERN DISTRICT


RICHARD THOMAS WALSH, EXECUTOR : No. 14 WAP 2019
OF THE ESTATE OF THOMAS J. WALSH, :
DECEASED                              : Appeal from the Order of the
                                      : Superior Court entered June 20,
                                      : 2018 at No. 1661 WDA 2016
             v.                       : vacating the Order of the Court of
                                      : Common Pleas of Allegheny County
                                      : entered October 14, 2016 at No. GD
BASF         CORPORATION;       BAYER : 10-018588, and remanding.
CORPORATION          D/B/A      BAYER :
CROPSCIENCE,      L.P.,  AND    BAYER : ARGUED: October 16, 2019
CROPSCIENCE HOLDING, INC., AND/OR :
BAYER CROPSCIENCE, L.P. AND BAYER :
CROPSCIENCE HOLDING, INC., IN THEIR :
OWN RIGHT; BIOSAFE SYSTEMS, L.L.C.; :
CHEMTURA CORPORATION; CLEARY :
CHEMICAL           CORP.;        DOW :
AGROSCIENCES, L.L.C.; E.H. GRIFFITH, :
INC.; E.I. DU PONT DE NEMOURS AND :
CO.,      INC.;  G.B.     BIOSCIENCES :
CORPORATION;         JOHN       DEERE :
LANDSCAPING, INC., SUCCESSOR TO :
LESCO, INC.; MONSANTO COMPANY; :
NUFARM AMERICAS, INC.; REGAL :
CHEMICAL CO.; SCOTTS-SIERRA CROP :
PROTECTION CO.; AND SYNGENTA :
CROP PROTECTION, INC.                 :
                                      :
                                      :
APPEAL OF: DOW AGROSCIENCES, :
L.L.C., BAYER CROPSCIENCE, L.P., :
BAYER CORPORATION, AND BAYER :
CROPSCIENCE HOLDING, INC.             :

RICHARD THOMAS WALSH, EXECUTOR : No. 15 WAP 2019
OF THE ESTATE OF THOMAS J. WALSH, :
DECEASED                          : Appeal from the Order of the
                                  : Superior Court entered June 20,
                                  : 2018 at No. 1661 WDA 2016,
             v.                            :   vacating the Order of the Court of
                                           :   Common Pleas of Allegheny County
                                           :   entered October 14, 2016 at No. GD
BASF         CORPORATION;       BAYER      :   10-018588, and remanding.
CORPORATION          D/B/A      BAYER      :
CROPSCIENCE,      L.P.,  AND    BAYER      :   ARGUED: October 16, 2019
CROPSCIENCE HOLDING, INC., AND/OR          :
BAYER CROPSCIENCE, L.P. AND BAYER          :
CROPSCIENCE HOLDING, INC., IN THEIR        :
OWN RIGHT; BIOSAFE SYSTEMS, L.L.C.;        :
CHEMTURA CORPORATION; CLEARY               :
CHEMICAL           CORP.;        DOW       :
AGROSCIENCES, L.L.C.; E.H. GRIFFITH,       :
INC.; E.I. DU PONT DE NEMOURS AND          :
CO.,      INC.;  G.B.     BIOSCIENCES      :
CORPORATION;         JOHN       DEERE      :
LANDSCAPING, INC., SUCCESSOR TO            :
LESCO, INC.; MONSANTO COMPANY;             :
NUFARM AMERICAS, INC.; REGAL               :
CHEMICAL CO.; SCOTTS-SIERRA CROP           :
PROTECTION CO.; AND SYNGENTA               :
CROP PROTECTION, INC.                      :
                                           :
                                           :
APPEAL OF: DEERE & COMPANY                 :

RICHARD THOMAS WALSH, EXECUTOR : No. 16 WAP 2019
OF THE ESTATE OF THOMAS J. WALSH, :
DECEASED                              : Appeal from the Order of the
                                      : Superior Court entered June 20,
                                      : 2018 at No. 1661 WDA 2016,
             v.                       : vacating the Order of the Court of
                                      : Common Pleas of Allegheny County
                                      : entered October 14, 2016 at No. GD
BASF         CORPORATION;       BAYER : 10-018588, and remanding.
CORPORATION          D/B/A      BAYER :
CROPSCIENCE,      L.P.,  AND    BAYER : ARGUED: October 16, 2019
CROPSCIENCE HOLDING, INC., AND/OR :
BAYER CROPSCIENCE, L.P. AND BAYER :
CROPSCIENCE HOLDING, INC., IN THEIR :
OWN RIGHT; BIOSAFE SYSTEMS, L.L.C.; :
CHEMTURA CORPORATION; CLEARY :
CHEMICAL           CORP.;        DOW :
AGROSCIENCES, L.L.C.; E.H. GRIFFITH, :
INC.; E.I. DU PONT DE NEMOURS AND :
CO.,      INC.;  G.B.     BIOSCIENCES :

[J-92A-2019, J-92B-2019, J-92C-2019, J-92D-2019 and J-92E-2019] [MO: Donohue, J.]
                                       -2-
CORPORATION;      JOHN     DEERE         :
LANDSCAPING, INC., SUCCESSOR TO          :
LESCO, INC.; MONSANTO COMPANY;           :
NUFARM AMERICAS, INC.; REGAL             :
CHEMICAL CO.; SCOTTS-SIERRA CROP         :
PROTECTION CO.; AND SYNGENTA             :
CROP PROTECTION, INC.                    :
                                         :
                                         :
APPEAL   OF:     SYNGENTA           CROP :
PROTECTION, INC.                         :

RICHARD THOMAS WALSH, EXECUTOR : No. 17 WAP 2019
OF THE ESTATE OF THOMAS J. WALSH, :
DECEASED                              : Appeal from the Order of the
                                      : Superior Court entered June 20,
                                      : 2018 at No. 1661 WDA 2016,
             v.                       : vacating the Order of the Court of
                                      : Common Pleas of Allegheny County
                                      : entered October 14, 2016 at No. GD
BASF         CORPORATION;       BAYER : 10-018588, and remanding.
CORPORATION          D/B/A      BAYER :
CROPSCIENCE,      L.P.,  AND    BAYER : ARGUED: October 16, 2019
CROPSCIENCE HOLDING, INC., AND/OR :
BAYER CROPSCIENCE, L.P. AND BAYER :
CROPSCIENCE HOLDING, INC., IN THEIR :
OWN RIGHT; BIOSAFE SYSTEMS, L.L.C.; :
CHEMTURA CORPORATION; CLEARY :
CHEMICAL           CORP.;        DOW :
AGROSCIENCES, L.L.C.; E.H. GRIFFITH, :
INC.; E.I. DU PONT DE NEMOURS AND :
CO.,      INC.;  G.B.     BIOSCIENCES :
CORPORATION;         JOHN       DEERE :
LANDSCAPING, INC., SUCCESSOR TO :
LESCO, INC.; MONSANTO COMPANY; :
NUFARM AMERICAS, INC.; REGAL :
CHEMICAL CO.; SCOTTS-SIERRA CROP :
PROTECTION CO.; AND SYNGENTA :
CROP PROTECTION, INC.                 :
                                      :
                                      :
APPEAL OF: MONSANTO COMPANY           :

RICHARD THOMAS WALSH, EXECUTOR : No. 18 WAP 2019
OF THE ESTATE OF THOMAS J. WALSH, :
DECEASED                          :

[J-92A-2019, J-92B-2019, J-92C-2019, J-92D-2019 and J-92E-2019] [MO: Donohue, J.]
                                       -3-
                                                   :   Appeal from the Order of the
                                                   :   Superior Court entered June 20,
                v.                                 :   2018 at No. 1661 WDA 2016,
                                                   :   vacating the Order of the Court of
                                                   :   Common Pleas of Allegheny County
    BASF         CORPORATION;       BAYER          :   entered October 14, 2016 at No. GD
    CORPORATION          D/B/A      BAYER          :   10-018588, and remanding.
    CROPSCIENCE,      L.P.,  AND    BAYER          :
    CROPSCIENCE HOLDING, INC., AND/OR              :   ARGUED: October 16, 2019
    BAYER CROPSCIENCE, L.P. AND BAYER              :
    CROPSCIENCE HOLDING, INC., IN THEIR            :
    OWN RIGHT; BIOSAFE SYSTEMS, L.L.C.;            :
    CHEMTURA CORPORATION; CLEARY                   :
    CHEMICAL           CORP.;        DOW           :
    AGROSCIENCES, L.L.C.; E.H. GRIFFITH,           :
    INC.; E.I. DU PONT DE NEMOURS AND              :
    CO.,      INC.;  G.B.     BIOSCIENCES          :
    CORPORATION;         JOHN       DEERE          :
    LANDSCAPING, INC., SUCCESSOR TO                :
    LESCO, INC.; MONSANTO COMPANY;                 :
    NUFARM AMERICAS, INC.; REGAL                   :
    CHEMICAL CO.; SCOTTS-SIERRA CROP               :
    PROTECTION CO.; AND SYNGENTA                   :
    CROP PROTECTION, INC.                          :
                                                   :
                                                   :
    APPEAL OF: BASF CORPORATION                    :


                                  CONCURRING OPINION


JUSTICE WECHT                                      DECIDED: JULY 21, 2020

        The Majority’s opinion, which I join, explains well the mischief that arises when trial

judges overestimate their role as keepers of the gate through which expert evidence must

pass.    Pursuant to Pennsylvania’s application of the Frye standard,1 a trial court

determining whether to admit expert testimony may consider only whether the expert


1       See Frye v. United States, 293 F. 1013 (D.C. 1923).



[J-92A-2019, J-92B-2019, J-92C-2019, J-92D-2019 and J-92E-2019] [MO: Donohue, J.]
                                       -4-
arrived at his opinion by employing principles and methods “generally accepted” in the

relevant community of experts. Conversely, under the Daubert standard,2 the prevailing

rubric in federal courts and in a majority of state courts, the trial court also may consider

whether the expert “reliably applied” the methodology in question and whether the

opinions and the conclusions that he or she reached are supported by “sufficient facts or

data.” See F.R.E. 702(d), (b) (respectively). For nearly thirty years, Pennsylvania has

rejected Daubert’s broader grant of authority—despite repeated invitations to adopt it.3 In

my view, Frye continues to present the superior approach. I write separately because I

am concerned that this Court’s decision in Betz v. Pneumo Abex L.L.C., 44 A.3d 27

(Pa. 2012), in its reliance upon potentially misleading terminology, so muddied the waters

that this Court should stabilize its characterization of the Frye standard as distinct from

Daubert, leaving no unnecessary doubt regarding the limitations upon a trial court’s

discretion in assessing the admissibility of expert evidence. Because the lower court and

Appellants alike relied upon Betz’ problematic terminology, I would take this opportunity

to set matters straight.




2        See Daubert v. Merrell Dow Pharm., Inc., 509 U.S. 579 (1993). Daubert is the first
in a “trilogy” of cases on the subject, consisting of Daubert and the United States Supreme
Court’s subsequent decisions in General Electric Co. v. Joiner, 522 U.S. 136 (1997), and
Kumho Tire Co., Ltd. v. Carmichael, 526 U.S. 137 (1999). See generally David E.
Bernstein & Jeffrey D. Jackson, The Daubert Trilogy in the States, 44 JURIMETRICS. J. 351
(2004).
3      As noted in his Dissenting Opinion, Chief Justice Saylor has in the past suggested
some affinity for Daubert. See Diss. Op. at 5-6 (citing Commonwealth v. Smith, 995 A.2d
1143, 1177 (Pa. 2010) (Saylor, J., concurring and dissenting)). In keeping with that,
excepting Pennsylvania cases, virtually every case Chief Justice Saylor cites to support
his substantive view in this case comes from a jurisdiction that adheres directly or in
practice to the Daubert standard.

[J-92A-2019, J-92B-2019, J-92C-2019, J-92D-2019 and J-92E-2019] [MO: Donohue, J.]
                                       -5-
       This Court’s preference for the Frye test is embodied in Pennsylvania Rule of

Evidence 702, which provides:

       A witness who is qualified as an expert by knowledge, skill, experience,
       training, or education may testify in the form of an opinion or otherwise if:
       (a) the expert’s scientific, technical, or other specialized knowledge is
       beyond that possessed by the average lay person; (b) the expert’s scientific,
       technical, or other specialized knowledge will help the trier of fact to
       understand the evidence or to determine a fact in issue; and (c) the expert’s
       methodology is generally accepted in the relevant field.

Pa.R.E. 702. Thus, when a party seeks to introduce an expert’s testimony, the trial court

must determine whether the principles and methodology employed by the expert in

developing his or her opinion are generally accepted in the relevant field.4 By doing so,

the court “ensures that the proffered evidence results from scientific research which has

been conducted in a fashion that is generally recognized as being sound, and is not the

fanciful creation[] of a renegade researcher.” Blum ex rel. Blum v. Merrell Dow Pharm.,

Inc., 764 A.2d 1, 9-10 (Pa. 2000) (Cappy, J., dissenting).

       Critically, this restriction “applies to an expert’s methods, not his conclusions.”

Grady v. Frito Lay, Inc., 839 A.2d 1038, 1047 (Pa. 2003); accord Maj. Op. at 17 (“While

the methodologies employed by the expert must be generally accepted, the conclusions

reached from those applications need not also be generally accepted.”). The Frye court

itself explained:

       Just when a scientific principle or discovery crosses the line between the
       experimental and demonstrable stages is difficult to define. Somewhere in
       this twilight zone the evidential force of the principle must be recognized,
       and while courts will go a long way in admitting expert testimony deduced
       from a well-recognized scientific principle or discovery, the thing from which


4      As the Majority observes, the proponent bears the burden of establishing that the
proffered testimony satisfies all three prongs of Rule 702. See Maj. Op. at 17 (citing
Grady v. Frito Lay, Inc., 839 A.2d 1038, 1045 (Pa. 2003)).

[J-92A-2019, J-92B-2019, J-92C-2019, J-92D-2019 and J-92E-2019] [MO: Donohue, J.]
                                       -6-
       the deduction is made must be sufficiently established to have gained
       general acceptance in the particular field in which it belongs.

Frye, 293 F. at 1014 (emphasis added).

       While we can agree with the United States Supreme Court that, in assessing the

admissibility of an expert’s testimony, a court should not turn a blind eye when an expert

connects his method to his conclusion only by the because-I-said-so of his “ipse dixit,”

Gen. Elec. Co. v. Joiner, 522 U.S. 136, 146 (1997), the Frye standard provides the

complementary restriction that the court may not rely upon its own ex cathedra appraisal

of the expert’s methods to exclude such evidence. The balance is struck by requiring the

court to rule based solely upon its assessment of the evidence and argument submitted

by the parties to establish or contradict such acceptance. See Grady, 839 A.2d at 1045

(“[R]equiring judges to pay deference to the conclusions of those who are in the best

position to evaluate the merits of scientific theory and technique when ruling on the

admissibility of scientific proof, as the Frye test requires, is the better way of [e]nsuring

that only reliable expert scientific evidence is admitted at trial.”). How effectively and

convincingly an expert employs a given methodology is a matter for the jury to assess.

       Our belief in the importance of the methods/conclusions distinction animates this

Court’s continued adherence to Frye. In a passage often cited by this Court, the United

States Court of Appeals for the District of Columbia Circuit explained:

       The requirement of general acceptance in the scientific community assures
       that those most qualified to assess the general validity of a scientific method
       will have the determinative voice. Additionally, the Frye test protects [both
       parties] by assuring that a minimal reserve of experts exists who can
       critically examine the validity of a scientific determination in a particular
       case. Since scientific proof may in some instances assume a posture of
       mystic infallibility in the eyes of a jury of laymen, the ability to produce
       rebuttal experts, equally conversant with the mechanics and methods of a
       particular technique, may prove to be essential.

[J-92A-2019, J-92B-2019, J-92C-2019, J-92D-2019 and J-92E-2019] [MO: Donohue, J.]
                                       -7-
United States v. Addison, 498 F.2d 741, 744-45 (D.C. Cir. 1974); see Commonwealth v.

Dengler, 890 A.2d 372, 381 (Pa. 2005) (quoting Addison); Commonwealth v. Topa, 369

A.2d 1277, 1282 (Pa. 1977) (same).

       Simply put, the trial court should ensure that a “renegade researcher” does not

appear before the jury robed in the implicit authority of an expertise that his or her

methodology calls into question. But once the court determines, with the assistance of

the proponent’s proofs and the accounts of fellow experts in the discipline, that the

analysis proceeds from generally accepted principles and methods, the court may

proceed no further.     Questions concerning the quality and persuasiveness of the

applications and conclusions must be resolved by the collective judgment of the jury.

Aided by the crucible of the parties’ adversarial presentations, the jury is just as capable

as the average judge of weighing the parties’ competing accounts, identifying and

rejecting particular applications of generally accepted principles and methods that either

depart from standard practice in the field or lack a sufficient evidentiary foundation.

       Daubert jurisdictions generally grant trial courts substantially broader discretion to

stop expert testimony at the courtroom door.5 Federal Rule of Evidence 702 provides:

       A witness who is qualified as an expert by knowledge, skill, experience,
       training, or education may testify in the form of an opinion or otherwise if:

5      In the interim between the enactment of Rule 702 in 1975 and the Daubert decision
in 1993, the advent of toxic tort litigation engendered concerns about the overly
permissive admission of what some have called “junk science.” During that spell, courts
applied increasingly disparate principles to determine the admissibility of expert evidence.
According to one commentator, “[b]y 1993, the year of Daubert, ‘the Supreme Court got
the message: [s]omething needed to be done.’” Jim Hilbert, The Disappointing History of
Science in the Courtroom: Frye, Daubert, and the Ongoing Crisis of “Junk Science” in
Criminal Trials, 71 OKLA. L. REV. 759, 779 (2019) (quoting Barbara Pfeffer Billauer,
Daubert Debunked: A History of Legal Retrogression and the Need to Reassess
“Scientific Admissibility,” 21 SUFFOLK J. TRIAL & APP. ADVOC. 1, 27 (2015-16)).

[J-92A-2019, J-92B-2019, J-92C-2019, J-92D-2019 and J-92E-2019] [MO: Donohue, J.]
                                       -8-
          (a) the expert’s scientific, technical, or other specialized knowledge will help
          the trier of fact to understand the evidence or to determine a fact in issue;

          (b) the testimony is based on sufficient facts or data;

          (c) the testimony is the product of reliable principles and methods; and

          (d) the expert has reliably applied the principles and methods to the facts of
          the case.

F.R.E. 702.        Subparagraphs (b) and (d) have no counterpart in Pennsylvania’s

corresponding rule, and it is there that the “gatekeeping” mandate in its strongest sense

lives.6

          Interestingly, the Daubert Court evidently deemed it necessary, or at least

beneficial, to address concerns that its interpretation of Rule 702 would loosen the

standard for admissibility relative to the Frye test, rather than empowering judges to guard

the courtroom more stringently than Frye allowed. Thus, while it underscored the Federal

Rules’ of Evidence “approach of relaxing the traditional barriers to ‘opinion’ testimony,”

and emphatically disagreed that Rule 702 implicitly preserved Frye’s “austere” general

acceptance requirement, the Court commented that Frye’s displacement “[did] not

mean . . . that the Rules themselves place no limits on the admissibility of purportedly

scientific evidence.” Daubert, 509 U.S. at 588-89.

          In keeping with this expectation, in a passage I embrace even though I reject the

rule it was formulated to support, the Daubert Court persuasively explained why courts

should apply a more permissive rather than unduly strict standard. In rejecting concerns

that abandoning the “general acceptance” criterion as such would leave “befuddled



6      The Court observed that Rule 702 “displaced” the Frye test. Daubert, 509 U.S.
at 589; accord Joiner, 522 U.S. at 142.

[J-92A-2019, J-92B-2019, J-92C-2019, J-92D-2019 and J-92E-2019] [MO: Donohue, J.]
                                       -9-
juries . . . confounded by absurd and irrational pseudoscientific assertions,” the Daubert

Court deemed the argument “overly pessimistic about the capabilities of the jury and of

the adversary system generally. Vigorous cross-examination, presentation of contrary

evidence, and careful instruction on the burden of proof are the traditional and appropriate

means of attacking shaky but admissible evidence.” Daubert, 509 U.S. at 595-96.

       Even several years later, the Joiner Court professed to believe that the Daubert

standard was more permissive in favor of the admission of expert evidence than the Frye

standard. See Joiner, 522 U.S. at 142 (“[W]hile the Federal Rules of Evidence allow

district courts to admit a somewhat broader range of scientific testimony than would have

been admissible under Frye, they leave in place the ‘gatekeeper’ role of the trial judge in

screening such evidence.”7). But in dismissing the Frye-based argument that the court

may consider only the general acceptance of methods while avoiding the reasoning

overlain upon that methodological foundation, the Court ensured otherwise, explaining:

       [C]onclusions and methodology are not entirely distinct from one another.
       Trained experts commonly extrapolate from existing data. But nothing in
       either Daubert or the Federal Rules of Evidence requires a district court to
       admit opinion evidence that is connected to existing data only by the ipse
       dixit of the expert. A court may conclude that there is simply too great an
       analytical gap between the data and the opinion proffered.

7      The Majority and Chief Justice Saylor disagree over the pertinence of the
“gatekeeping” terminology endemic to the law concerning the admissibility of evidence in
both Frye and Daubert jurisdictions. Compare Maj. Op. at 20 (“Whether we refer to the
role of the trial court in a Frye contest as that of a “gatekeeper” is not consequential.”),
with Diss. Op. at 5 (noting that gatekeeping “is the clear purport of most of this Court’s
decisions on the subject”). As the quotation from Joiner makes clear, the gatekeeper
terminology is a commonplace in both Frye and Daubert case law. Moreover, it is not
inapt to say that the trial court acts as a gatekeeper in determining the admissibility of
evidence generally. Nonetheless, I generally avoid the gatekeeper terminology, because
at least colloquially it suggests a more jealously guarded portal than the Frye test calls
for.



[J-92A-2019, J-92B-2019, J-92C-2019, J-92D-2019 and J-92E-2019] [MO: Donohue, J.]
                                       - 10 -
Id. at 146.

       Daubert’s and Joiner’s protestations soon proved unwarranted. As Professor

Bernstein observed less than a decade after the decision issued, “Daubert, particularly

as extended by Joiner and Kumho Tire,[8] ha[d] become a far broader and stricter test

than Frye ever was.” David E. Bernstein, Frye, Frye, Again: The Past, Present, and

Future of the General Acceptance Test, 41 JURIMETRICS. J. 385, 404 (2001) (hereinafter

“Frye, Frye, Again”); cf. Hilbert, supra n.5, at 791-92 (noting continuing dispute about

whether Daubert in fact increased the frequency with which expert evidence was

excluded in federal courts).

       To some extent, the tension between the Court’s stated impression that Frye was

more stringent than Daubert and the fact that Daubert emerged as the stricter test of the

two may be explained by differences in the forms each takes in various jurisdictions.

Merely citing Frye or Daubert as the governing standard furnishes no assurance of

consistency of application. See generally Frye, Frye, Again, 41 JURIMETRICS. J. at 397-

98 (observing that Frye jurisdictions were ruling inconsistently on the question of whether

a court may only examine methodology for general acceptance or also consider the

relative acceptance of the expert’s conclusions).       More recently, one commentator

counted twenty-five states that have a rule of evidence that mirrors Federal Rule 702 and

purport to follow Daubert, fifteen states that apply Frye in more or less its original form,

another half-dozen states that do not reject Frye outright but apply Daubert factors in




8      See Kumho Tire Co., Ltd. v. Carmichael, 526 U.S. 137 (1999). The Court in Kumho
Tire extended application of the Daubert test to all expert testimony, not just “scientific”
testimony. See id. at 141.

[J-92A-2019, J-92B-2019, J-92C-2019, J-92D-2019 and J-92E-2019] [MO: Donohue, J.]
                                       - 11 -
practice, and four states that follow a test somewhat of their own devising. See Samuel

D. Hatch, Where Are the Gatekeepers? Challenging Utah’s Threshold Standard for

Admissibility of Expert Witness Testimony, 2018 UTAH L. REV. 1123, 1140 (2018). And

as far back as 2001, Professor Bernstein observed what he identified as a convergence

in practice of the Frye and Daubert tests. See Frye, Frye, Again, 41 JURIMETRICS J. at 385.

       Regardless, in my view what the Daubert Court characterized as Frye’s “austerity”

manifests in Pennsylvania practice not in an overly exclusionary effect, but rather in its

assurance that the trial court does not adopt too expansive a view of its important but

limited role in ensuring that only qualified expert evidence reaches a jury. And it should

surprise no one that a test that asks only whether a given “expert’s methodology is

generally accepted in the relevant field,” Pa.R.E. 702(c), will result in the admission of

more evidence than one that requires the court to assess whether the expert’s “principles

and methods” are “reliable” (a criterion I read as similar in practice to general acceptance),

and determine for itself whether the “testimony is based on sufficient facts or data,” and

assess whether “the expert has reliably applied the principles and methods to the facts.”

F.R.E. 702 (emphasis added).

       As though that were not enough, the Daubert Court cited four additional

considerations as relevant: (1) whether the theory or technique at issue “can be (and has

been) tested”; (2) “whether the theory or technique has been subjected to peer review

and publication”; (3) “in the case of a particular scientific technique, . . . the known or

potential rate of error . . . and the existence and maintenance of standards controlling the

technique’s operation”; and (4) “general acceptance,” because “[w]idespread acceptance

can be an important factor in ruling particular evidence admissible, and a known


[J-92A-2019, J-92B-2019, J-92C-2019, J-92D-2019 and J-92E-2019] [MO: Donohue, J.]
                                       - 12 -
technique which has been able to attract only minimal support within the community may

properly be viewed with skepticism.” Daubert, 509 U.S. at 593-94 (cleaned up). In theory,

each factor presents a distinct basis for exclusion, and thus each factor, too, exponentially

increases the likelihood of inconsistent application.9

       With thirty or more states applying Daubert, Pennsylvania remains a Frye stalwart.

In Grady, we expressed clearly why we prefer Frye:

       One of the primary reasons we embraced the Frye test in Topa was its
       assurance that judges would be guided by scientists when assessing the
       reliability of a scientific method. Given the ever-increasing complexity of
       scientific advances, this assurance is at least as compelling today as it was
       in 1977, when we decided that case. We believe now, as we did then, that
       requiring judges to pay deference to the conclusions of those who are in the
       best position to evaluate the merits of scientific theory and technique when
       ruling on the admissibility of scientific proof, as the Frye rule requires, is the
       better way of [e]nsuring that only reliable expert scientific evidence is
       admitted at trial.

       We also believe that the Frye test, which is premised on a rule—that of
       “general acceptance”—is more likely to yield uniform, objective, and
       predictable results among the courts, than is the application of the Daubert
       standard, which calls for a balancing of several factors. Moreover, the
       decisions of individual judges, whose backgrounds in science may vary
       widely, will be similarly guided by the consensus that exists in the scientific
       community on such matters.



9      Later, the Court observed:
       [W]e can neither rule out, nor rule in, for all cases and for all time the
       applicability of the factors mentioned in Daubert, nor can we now do so for
       subsets of cases categorized by category of expert or by kind of evidence.
       Too much depends upon the particular circumstances of the particular case
       at issue.
Kumho Tire, 526 U.S. at 150; see id. at 151 (“[Daubert] made clear that its list of factors
was meant to be helpful, not definitive.”). Highlighting just one potential concern,
Professor Hilbert notes “profound disparities in how Daubert has been applied, both
between civil and criminal contexts, and between parties in each context,” including “a
double standard” favoring respectively civil defendants and prosecutors. See Hilbert,
supra n.5, at 796.

[J-92A-2019, J-92B-2019, J-92C-2019, J-92D-2019 and J-92E-2019] [MO: Donohue, J.]
                                       - 13 -
Grady, 839 A.2d at 1044-45.

       In Betz, however, our fidelity to these principles was undermined in a subtle but

potentially important manner.     Specifically, Betz introduced into Pennsylvania law a

“conventionality” requirement, suggesting that expert testimony in a scientific discipline is

admissible only when the expert has “applied accepted scientific methodology in a

conventional fashion in reaching his or her conclusions.” Betz, 44 A.3d at 53 (emphasis

added). This conventional application requirement, however, cannot be found in Topa,

Grady, or the Pennsylvania Frye cases that followed, and it sounds very much like Federal

Rule 702’s direction that the court assess whether “the expert has reliably applied the

principles and methods to the facts of the case.” F.R.E. 702(d) (emphasis added). This

at least gestures toward the more probing, credibility-inflected Daubert inquiry, which we

squarely rejected in Grady. I fear that Betz’ conventional application overlay purports or

operates to require a court to assess something beyond the general acceptance of a

given expert’s methods.

       I can find in Pennsylvania law no pre-Betz source for the conventional application

formulation. But this Court has recycled Betz’ language on numerous occasions since

then. See Mitchell v. Shikora, 209 A.3d 307, 319 n.12 (Pa. 2019); Commonwealth v.

Jacoby, 170 A.3d 1065, 1090-91 (Pa. 2017)10; Commonwealth v. Walker, 92 A.3d 766,

790 (Pa. 2014); see also Commonwealth v. Treiber, 121 A.3d 435, 488 (Pa. 2015)




10     As my authorship in Jacoby attests, I am not blameless in uncritically repeating
Betz’ formulation.



[J-92A-2019, J-92B-2019, J-92C-2019, J-92D-2019 and J-92E-2019] [MO: Donohue, J.]
                                       - 14 -
(Saylor, C.J., dissenting).11 I believe that repeating Betz’ Daubert-esque language can

only erode this Court’s commitment to Frye’s narrow focus upon the expert’s underlying

principles and methodology.12


11     The Superior Court has followed our lead in precedential opinions, including in this
case, see Walsh v. BASF Corp., 191 A.3d 838, 844 (Pa. Super. 2018); Commonwealth
v. Nevels, 203 A.3d 229, 237-38 (Pa. Super. 2019); Commonwealth v. Freeman,
128 A.3d 1231, 1246 (Pa. Super. 2015), and in several non-precedential memoranda.
12      Chief Justice Saylor is correct that in Betz, as in this Court’s cases that have quoted
its formulation since, the conventional application terminology was used narrowly as a
basis to identify novel science for purposes of determining whether to conduct a Frye
inquiry in the first instance. But I disagree that Daubert-esque terminology presents no
risk of “confusi[on], at all.” Diss. Op. at 15. To confirm that the Chief Justice’s optimism
is misplaced, one need look no further than the sentence that introduces Appellants’ brief
in this case: “Recognizing that any causation opinion must be premised on a generally
accepted methodology applied in a conventional fashion, [the trial court] excluded
Plaintiff’s experts for failing to meet Pennsylvania’s Frye standard.” Appellants’ Brief at 1.
Appellants later add that “[a]ny methodology, even if generally accepted, must be applied
‘in a conventional fashion’ to satisfy Frye.” Appellants’ Reply Brief at 12 (quoting Betz,
44 A.3d at 53) (emphasis added). These “conventionality” usages do not recognize or
embody the Dissent’s proffered limitation, especially given the pervasiveness of their
recurrences with and without citation to Betz. See, e.g., Appellant’s Brief at 21 (citing
Betz, incorrectly by the Majority’s lights), 34 (same), 35 (ascribing the conventional
application requirement to Blum, supra); see also Appellants’ Reply Brief at 5, 8 (ascribing
the conventional application requirement to Mitchell, supra). In its published decision, the
court below manifested precisely the same confusion. See Walsh, 191 A.3d at 844 (“Frye
requires that a proponent of novel scientific testimony demonstrate that the expert relied
upon and conventionally applied a scientific method generally accepted in the relevant
scientific community.”).
         The notion of bright lines in the Frye approach has always been somewhat fanciful.
The Frye court observed that, “while courts will go a long way in admitting expert
testimony deduced from a well-recognized scientific principle or discovery, the thing from
which the deduction is made must be sufficiently established to have gained general
acceptance in the particular field in which it belongs.” Frye, 293 F. at 1014. But reading
Frye and Betz in tandem, to find this enterprise as straightforward as the Dissent suggests
it is or should be, we would need to clearly distinguish the “application” of a given principle
(relevant to whether to conduct a Frye inquiry in the first instance) from the expert’s
“deduction” from that principle (relevant to whether the deduction passes Frye test), which
strikes me as a quixotic aspiration. Courts seeking tidiness and clarity will search the
Frye/Daubert morass in vain; all we can hope to do is avoid excess confusion where
possible.



[J-92A-2019, J-92B-2019, J-92C-2019, J-92D-2019 and J-92E-2019] [MO: Donohue, J.]
                                       - 15 -
       The conventional application requirement encourages litigation tactics familiar to

Daubert jurisdictions and rewarded by the trial court in this case. In denying the admission

of all causation testimony, the trial court all but erased the defining distinction between

Frye and Daubert. Although the trial court did not cite Betz’ formulation of the Frye

standard, the court’s detailed review of the many studies and sources cited by Nachman

Brautbar, M.D., was replete with the court’s own disagreements regarding the application

of the methods and data delineated in the studies themselves. Nowhere in the court’s

two supporting opinions did it rely substantially upon the expert evidence that Defendants

adduced to challenge the general acceptance of Plaintiff’s experts’ methods. Thus, we

have no reason to believe that the trial court was persuaded by Defendants’ Frye

evidence rather than by its own unbounded frolic through the literature.13




13      In this regard, the Chief Justice seeks both to validate this aspect of the trial court’s
approach and to buttress it with a handful of references to Defendants’ countervailing
Frye evidence. See Diss. Op. at 6-14. But the trial court never cited anything but its own
independent survey of Plaintiff’s expert evidence as a basis for excluding that evidence.
This calls into question the degree to which the trial court concerned itself with the
competing evidentiary showings on general acceptance, and it is not an appellate court’s
function to fill that critical void in the trial court’s account of its own reasoning.
Furthermore, I disagree with the Dissent’s suggestion that constraining the court to
consider only the parties’ competing presentations regarding general acceptance
“imposes an unreasonable constraint on the trial courts’ ability to perform the essential
review for reliability.” Id. at 11. The very invocation of a trial court assessment of
“reliability” hearkens back to the Federal Rule and Daubert considerations, and what
concerns me is precisely the risk of that sort of Daubert-ization of our Frye standard.
Nothing about our law to date precludes a trial court from looking to the documentation
submitted in support of a given scientific method. But the court’s review must be
channeled by the adversarial presentations of the parties’ Frye experts, not limited only
by the scope of the trial court’s intellectual ambition and willingness to pursue the matter
independently.



[J-92A-2019, J-92B-2019, J-92C-2019, J-92D-2019 and J-92E-2019] [MO: Donohue, J.]
                                       - 16 -
       To the extent that the trial court acknowledged the methods/application argument

at all, it did so only by dispatching a strawman. The court unfairly reduced Plaintiff’s

position to the proposition that the mere introduction of any literature, no matter how inapt,

takes the admissibility determination from the court’s hands. According to the trial court’s

account of Plaintiff’s argument, “Dr. Brautbar may cite a study regarding traffic patterns

in New York City for the proposition that Chemical A causes [disease] in humans.” Tr.

Ct. Supp. Memo., 12/27/2016, at 6. But the specter of a court powerless to exclude

evidence once any literature is introduced, however irrelevant, is absurd on its face; one

need not plumb the depths of that literature to discern patent irrelevance. Indeed, if such

irrelevance were at issue here, the trial court’s opinion would not be so voluminous in

characterizing and parsing and finding wanting or inapplicable Dr. Brautbar’s supporting

materials.14

       Some of our Commonwealth’s fine trial judges may well have the wisdom of

Solomon; certainly we aspire. But even Solomon did not have a medical degree or a



14      The Chief Justice pummels the same strawman when he presents the false choice
between “permitting trial courts to consider whether experts actually adhere to the
methodology that they only facially espouse” or “accept[ing] the sort of expert self-
validation which is of great concern to most courts.” Diss. Op. at 18. By no means do I
believe, nor would I hold, that a court cannot identify and discard inferences and
conclusions wholly divorced from their purported basis. Rather, I merely underscore the
proposition, long-embraced by this Court, that trial courts should exercise considerable
restraint in doing so. They do so foremost by focusing upon the Frye evidence adduced
by the parties rather than deputizing themselves—as the trial court did in this case—to
do the sort of sua sponte deep dive into the literature that the trial court performed in this
case. Cf. Maj. Op. at 20-21 (“The trial court may consider only whether the expert applied
methodologies generally accepted in the relevant field, and may not go further to attempt
to determine whether it agrees with the expert’s application of those methodologies or
whether the expert’s conclusions have sufficient factual support. Those are questions for
the jury to decide.” (footnote omitted)). Trial courts further advance this principle in close
cases by erring in favor of admitting the contested evidence.

[J-92A-2019, J-92B-2019, J-92C-2019, J-92D-2019 and J-92E-2019] [MO: Donohue, J.]
                                       - 17 -
doctorate, and wisdom is no substitute for subject matter expertise. A trial court should

not deny a litigant the benefit of a chosen expert because, after the court’s unilateral and

“intensely granular” screening, see Maj. Op. at 24 n.9, something about the sources upon

which the expert relies triggers the court’s doubt. Our judges are appointed or elected

from the ranks of lawyers whose knowledge and experience span the gamut of legal

specialties, but seldom involve ever-increasingly esoteric areas of technical and scientific

inquiry. In our adversarial system, judges are generalists, whom we ask to manage, but

not to drive, jury trials. In France’s inquisitorial system, jurists are selected to undergo a

rigorous, multi-year training program, culminating for some in the completion of a thirty-

one-month course of study in legal topics as well as sociology, psychology, psychiatry,

forensic science, pathology, and accounting, which is in keeping with the greater degree

to which French judges actively participate in the truth-determining process.15 But this is

not France.

       Our necessary reliance upon judges who lack the expertise to determine what

evidence should reach a jury creates certain risks that are exacerbated by the Daubert

standard. Thus, commentators have expressed reservations about jurists’ ability to apply

Daubert consistently, noting, for example, that “Daubert places a greater epistemic

burden [than Frye] on judges tasked with determining the reliability of proposed expert

testimony.” James R. Dillon, Expertise on Trial, 19 COLUM. SCI. & TECH. L. REV. 247, 262




15      See Kelly Buchanan, The French National School for the Judiciary, IN CUSTODIA
LEGIS:       LAW       LIBRARIANS      OF     CONGRESS         (Jan.       26,   2011),
https://blogs.loc.gov/law/2011/01/the-french-national-school-for-the-judiciary/.



[J-92A-2019, J-92B-2019, J-92C-2019, J-92D-2019 and J-92E-2019] [MO: Donohue, J.]
                                       - 18 -
(2018). Indeed, Prof. Steiner-Dillon16 submits “that judges generally cannot apply the

Daubert test with a level of competence necessary to satisfy intellectual due process.” Id.

at 272. By contrast, “[t]he Frye test delegates the question of reliability to a community

of recognized experts.      The court’s task consists only in identifying the relevant

community and determining whether it generally accepts the methodology at issue.” Id.

at 260.17 Anticipating this concern, Chief Justice Rehnquist commented in Daubert: “I do


16      A doctoral candidate when he published the cited article, Prof. Steiner-Dillon, née
Dillon, joined the faculty of the University of Dayton School of Law in 2018, the same year
the article appeared.
17     Professor Steiner-Dillon notes that Frye is not without its own difficulties:
       [T]he knottiest problem posed by Frye is the definition of the relevant
       community: if the reliability inquiry is a matter of nose counting, whose
       noses are to be counted? This is a problem of great practical import
       because domains or sub-disciplines often have disciplinary axioms and
       epistemic norms that lead them to view the reliability of a particular
       methodology quite differently. Closely related to the problem of identifying
       the relevant community is the problem of identifying its boundaries. Should
       the community be defined broadly or narrowly? As Cole and Edmond
       observe, “[c]ontestation over whether the [reference community] should be
       construed narrowly or broadly is endemic to a Frye analysis. . . . [N]arrow
       interpretations tend to favor proponents of contested evidence whereas
       broad interpretations tend to favor opponents and exclusion.”
Dillon, 19 COLUM. SCI. & TECH. L. REV. at 262 (footnotes omitted) (quoting Simon A. Cole
& Gary Edmond, Science without Precedent: The Impact of the National Research
Council Report on the Admissibility and Use of Forensic Science Evidence in the United
States, 4 BRIT. J. AM. LEGAL STUD. 586, 606 (2015)).
       The Chief Justice observes that Prof. Steiner-Dillon expresses similar concerns
regarding the ability of jurors to digest scientific evidence. Diss. Op. at 21. He further
notes that Prof. Steiner-Dillon proposes that courts appoint a sort of scientific ombudsman
to take on the expert evidence screening function and conduct independent research,
measures more consistent with the inquisitorial system noted above than with our
adversarial system, flawed though it may be. Id. at 22; cf. Gerald Walpin, America’s
Adversarial & Jury Systems: More Likely to Do Justice, 26 HARV. J. LAW & PUB. POLICY 175,
175-76 (2003) (observing, pace Winston Churchill, that “the adversarial system may be
the worst form of judicial procedure except for all others than have been tried from time
to time”). But that he identifies similar infirmities in both judges and juries attempting to


[J-92A-2019, J-92B-2019, J-92C-2019, J-92D-2019 and J-92E-2019] [MO: Donohue, J.]
                                       - 19 -
not doubt that Rule 702 confides to the judge some gatekeeping responsibility in deciding

questions of the admissibility of proffered expert testimony. But I do not think it imposes

on them either the obligation or the authority to become amateur scientists in order to

perform that role.” Daubert, 509 U.S. at 600-01 (Rehnquist, C.J., concurring in part and

dissenting in part). In keeping with Frye, I would relieve trial courts of the burden of trying.

       Betz and this Court’s subsequent, related decision in Rost v. Ford Motor Co., 151

A.3d 1032 (Pa. 2016), are most notable for their contribution to the law governing the use

and effect of “any exposure” causation testimony in toxic torts, and with respect to

asbestos specifically.18 In Betz, applying the above-reproduced standard, the Court

appeared to hold, and unquestionably implied, that when an expert testifies that any

exposure to a toxic substance enhances the risk that the exposed party will suffer injury

as a consequence of that particular exposure, the expert inadmissibly suggests that the

exposure in question, even when de minimis, is a substantial cause of the injury. In Rost,

this Court carefully limited that holding, observing that it applied only where the expert in

question rested its opinion regarding substantial causation entirely on that de minimis

exposure in reliance upon the any-exposure theory. Conversely, where an expert testifies

to that theory, which is not controversial as a general principle, but also testifies that the

plaintiff’s exposure to a given toxic substance was greater than de minimis and

substantially causative based upon an individualized application of the frequency,


assess the credibility and merit of expert presentations does not detract from my view
that, when in doubt, we must trust juries to glean the more convincing expert account
through our time-honored adversarial process.
18    See Diss. Op. at 7-8 n.2 (noting that Rost has yet to be applied outside the
asbestos context).



[J-92A-2019, J-92B-2019, J-92C-2019, J-92D-2019 and J-92E-2019] [MO: Donohue, J.]
                                       - 20 -
regularity, and proximity test,19 the testimony suffices to create a jury question regarding

substantial causation. Thus, Rost served as a bulwark against the potential for overbroad

application of Betz’ very narrow ruling. In effect, Rost solidified what was best from Betz

and distanced the Court from an unduly broad understanding of what remained.20

       The only distinctive, indeed singular, aspect of Betz that remains—the only thing

in Betz that cannot be conveyed more effectively by citing Rost—is the “conventional

application” language, which threatens to smuggle Daubert’s more expansive ideas about

judges’ role in determining the admissibility of expert evidence into Pennsylvania law.

Among the most worrisome potential effects of Betz’ conventional application requirement

is that it casts into doubt the proponent’s ability to bring rigorous scientific innovation to

the matter, leaving the law—and more importantly jurors—behind as science passes it

by. Thus, our law has retained Frye’s focus upon the general acceptance of the theory

or technique underlying expert testimony, rather than how or what an expert extrapolates

from it, keeping the door open to innovative applications of accepted principles and

methodologies.

       While the point may seem finely drawn, when we hold the line at conventional

application, we suggest that there is no more room for novelty than an expert venturing a


19     See generally Gregg v. V-J Auto Parts, Co., 943 A.2d 216 (Pa. 2007).
20     I fail to see how anything in this discussion indicates that I view Rost as overruling
Betz, or even deviates much from the Chief Justice’s previously-stated view. See Diss.
Op. at 18 n.11; cf. Rost, 151 A.3d at 1057 (Saylor, C.J., dissenting) (characterizing the
Majority as “cabin[ing]” Betz). I simply believe that Betz’ utility is substantially diminished
in the wake of Rost, which Chief Justice Saylor accurately observes “work[ed] a distinct
retrenchment relative to Betz.” Diss. Op. at 18, n.11. I further believe that Betz’
jurisprudential value is substantially undermined by its introduction of the “conventional
application” formulation.



[J-92A-2019, J-92B-2019, J-92C-2019, J-92D-2019 and J-92E-2019] [MO: Donohue, J.]
                                       - 21 -
novel final opinion or conclusion, and even that only if the expert arrived there using

entirely “conventional” means—all as assessed by a judge who, more likely than not, is

not conversant enough in the relevant discipline to confidently opine on conventionality

at all.21 Because I do not agree that it is jurisprudentially sound or consistent with

Pennsylvania law to risk usurping the role of the jury by overzealous application of Betz’

“conventional application” criterion, I believe that this terminology unnecessarily

complicates Pennsylvania’s Frye jurisprudence and should be avoided in this and future

Frye cases.

       As the Majority explains, the trial court wandered far afield of interrogating

Dr. Brautbar’s methods, clearly rendering its own sua sponte judgment with regard to the

worth of the studies Dr. Brautbar cited in support of his methods and conclusions, as well

as its apparently independent judgments as to abstruse questions concerning the

postulates, inferences, and conclusions Dr. Brautbar gleaned from these numerous

sources and the record in this case. In doing so, the court did far more than rely solely

upon the competing accounts provided by the parties’ experts, and so it exceeded the

bounds of its discretion. Accordingly, I join the Majority’s analysis.




21     Even the Kumho Tire Court recognized a species of this concern, noting that “[i]t
might not be surprising in a particular case, for example, that a claim made by a scientific
witness has never been the subject of peer review, for the particular application at issue
may never previously have interested any scientist.” Kumho Tire, 526 U.S. at 151.

[J-92A-2019, J-92B-2019, J-92C-2019, J-92D-2019 and J-92E-2019] [MO: Donohue, J.]
                                       - 22 -
