Lance Belville v. Ford Motor Company , 919 F.3d 224 ( 2019 )


Menu:
  •                                        PUBLISHED
    UNITED STATES COURT OF APPEALS
    FOR THE FOURTH CIRCUIT
    No. 18-1470
    LANCE R. BELVILLE; DONALD C. CARR; MINDI STEWART; STANLEY
    STEWART; CHARLES JOHNSON; JILL DURANT; MICHAEL ANTRAMGARZA;
    QUINTIN WILLIAMS; ACA LEGAL INVESTIGATIONS, INC.; JOHN MCGEE;
    DAVID H. PATTON; INEZ A. PATTON; PAMELA D. SMITH; BETTY J. TRINQUE;
    SHARON SHAFFER; ROBERT BRANDON; DANIEL GALLEGOS; TIMOTHY
    MATTHEWS; SAMUEL HAIRSTON; RHODA JEFFERS; MARY PHIPPEN;
    JONATHAN POMA; SHELLEY RILEY; CHARLES T. BURD; WILLIAM S.
    TROUTMAN; SHANE MAYFIELD; ANDREA MARTIN; THOMAS PORTER;
    HASEN DESIGN BUILD & DEVELOPMENT, INC.,
    Plaintiffs – Appellants,
    and
    DEAN RICHARDSON; CHRISTINE SALAMONE; BEVERLY GORTON; JOSH
    LEGATO; ROOFWERKS, INC.; MILLS ALLISON; LAURA ELSINGER, and;
    GABRIEL KLETSCHKA, Individually and on behalf of all others similarly situated;
    CAROLYN CHASE; GREG PEET; TONY BURNETT; GEORGE SHAFFER;
    ROBERT AGRIS; JOHN E. GRIMALDI; JOLENE HARRIS,
    Plaintiffs,
    v.
    FORD MOTOR COMPANY,
    Defendant – Appellee.
    Appeal from the United States District Court for the Southern District of West Virginia,
    at Huntington. Robert C. Chambers, District Judge. (3:13-cv-06529)
    Argued: January 29, 2019                                      Decided: March 25, 2019
    Before AGEE and HARRIS, Circuit Judges, and DUNCAN, Senior Circuit Judge.
    Affirmed by published opinion. Judge Agee wrote the opinion, in which Judge Harris
    and Senior Judge Duncan joined.
    ARGUED: John E. Tangren, DICELLO LEVITT & CASEY LLC, Chicago, Illinois, for
    Appellants. Jonathan D. Hacker, O’MELVENY & MYERS LLP, Washington, D.C., for
    Appellee. ON BRIEF: Adam J. Levitt, John E. Tangren, DICELLO LEVITT & CASEY
    LLC, Chicago, Illinois; Niall A. Paul, SPILMAN THOMAS & BATTLE, PLLC,
    Charleston, West Virginia; Gregory M. Travalio, Mark H. Troutman, Shawn K. Judge,
    ISAAC WILES BURKHOLDER & TEETOR, LLC, Columbus, Ohio, for Appellants.
    Sarah Virginia Bondurant Price, MCGUIREWOODS LLP, Richmond, Virginia;
    Jonathan D. Hacker, Bradley N. Garcia, O’MELVENY & MYERS LLP, Washington,
    D.C., for Appellee.
    2
    AGEE, Circuit Judge:
    A group of individuals and corporations sued Ford Motor Company for an alleged
    defect in their purchased or leased Ford vehicles manufactured between 2002 and 2010.
    The district court dismissed various claims of certain Plaintiffs, excluded the opinions of
    the Plaintiffs’ three experts, and granted summary judgment to Ford on all claims.
    Twenty-seven individual and two corporate Plaintiffs1 now appeal and, for the reasons set
    out below, we affirm the judgment of the district court.
    I.
    In 2013, various individuals and corporations filed three related actions in the
    Southern District of West Virginia, alleging that their Ford vehicles had a defective
    electronic throttle control (“ETC”) system, which could lead to an unintended
    acceleration (“UIA”). They further alleged that to prevent a UIA, Ford should have
    equipped their vehicles with an alternative failsafe system such as a Brake Over
    Accelerator (“BOA”). Based on this theory of defect, the Plaintiffs asserted numerous
    state and federal claims, including a violation of the Magnuson–Moss Warranty Act,
    breach of implied and express warranty, unjust enrichment, and a violation of state
    consumer protection statutes.
    1
    Plaintiffs in the proceedings below included Appellants as well as fourteen other
    individuals and one corporation. These other Plaintiffs did not file a notice of appeal. For
    convenience and to avoid confusion, we will identify all plaintiffs below as “Plaintiffs,”
    which includes Appellants.
    3
    Despite the alleged defect, only sixteen Plaintiffs alleged that they actually
    experienced UIAs, and none had suffered personal injury or property damage from the
    alleged defect. Nonetheless, all Plaintiffs sought economic damages arguing that the
    alleged defect made their vehicles worth less than their purchase or lease price.
    Specifically, they requested “damages to recover for diminished value at the time of
    purchase,” Belville v. Ford Motor Co., 
    13 F. Supp. 3d 528
    , 535 (S.D.W. Va. 2014),
    which they posit on appeal is—for “many” Plaintiffs— “the market price to repair the
    defective Class Vehicles.” Reply Br. 17.
    Ford filed motions to dismiss all three actions, which the district court granted in
    part and denied in part. Bellville, 13 F. Supp. 3d at 530. In 2014, the court dismissed,
    among other claims, the warranty and unjust enrichment claims of those Plaintiffs who
    had not experienced a UIA because they “failed to demonstrate a plausible claim that
    they paid more for their vehicles than their actual worth when they have used their
    vehicles without incident for many years.” Id. at 542. After the dismissal order was
    issued, the Plaintiffs twice attempted to amend their complaints. In considering the
    motions to amend, the district court clarified which claims were dismissed, consolidated
    the three actions into one, and directed the Plaintiffs to file a consolidated amended
    complaint consistent with the court’s orders.
    In December 2015, seventeen individuals and two corporations, as the Plaintiffs in
    the consolidated action, filed a Second Amended Master Consolidated Class Action
    4
    Complaint, 2 which became the operative complaint. As distinguished from the initial
    complaints, all but two Plaintiffs 3 now alleged that they experienced a UIA due to a
    defective ETC system in their Ford vehicles. Based on this alleged defect, the Plaintiffs
    continued to assert one federal claim—a violation of the Magnuson-Moss Warranty
    Act—and numerous state claims, including breach of express and implied warranty, fraud,
    and unjust enrichment claims.
    Ford moved to exclude the Plaintiffs’ expert witnesses and for summary judgment.
    By order of February 27, 2018, the district court granted partial summary judgment to
    Ford on the warranty and unjust enrichment claims, noting that because many factors
    unrelated to an ETC system may cause UIAs, the Plaintiffs’ mere allegations that they
    experienced UIAs were not evidence of a defect. See Johnson v. Ford Motor Co., 
    310 F. Supp. 3d 699
     (S.D.W. Va. 2018). It observed that to survive Ford’s motion for summary
    judgment, the Plaintiffs must establish “a causal link between their alleged [UIAs] and
    2
    The Plaintiffs moved for class certification in January 2018, but the district court
    granted summary judgment on all claims to Ford before ruling on this motion. Thus, the
    court never certified a class.
    3
    In the initial complaints, sixteen Plaintiffs, including Roofwerks, Inc., Greg Peet,
    Carolyn Chase, Robert Agris, and John Grimaldi, alleged that they experienced UIAs.
    With the district court’s permission, Roofwerks, Peet, Chase, Agris and Grimaldi
    voluntarily dismissed their claims.
    Nineteen of the Plaintiffs who survived the dismissal orders became the Plaintiffs
    in the consolidated action. This group included eleven Plaintiffs who alleged in the initial
    complaints that they experienced UIAs. The six other Plaintiffs changed their stance and
    alleged in the amended complaint that they experienced UIAs. Two Plaintiffs, John
    McGee and Hasen Design Build & Development, Inc., did not allege that they
    experienced UIAs or assert any warranty or unjust enrichment claims. All Plaintiffs in the
    consolidated action are parties to this appeal.
    5
    the alleged defect.” Id. at 704. The district court held the Plaintiffs failed to produce
    evidence of causation, explaining:
    none of [Plaintiffs’ proposed] experts can say that, for those Plaintiffs who
    alleged they experienced [a UIA], their events were the result of the alleged
    defect with the ETC system. Quite simply, Plaintiffs produced no experts
    who can testify that [their] alleged [UIAs] were proximately caused by the
    alleged defect rather than some other known cause for such events.
    Id. at 706–07. The court found, “this gap between Plaintiffs’ experts’ opinions and what
    allegedly occurred in Plaintiffs’ specific vehicles fatal to Plaintiffs’ warranty and unjust
    enrichment claims.” Id. at 707.
    By order of March 26, 2018, the district court resolved the Plaintiffs’ remaining
    claims. Johnson v. Ford Motor Co., No. 3:13-6529, 
    2018 WL 1512377
     (S.D.W. Va. Mar.
    26, 2018). The district court first granted Ford’s motion to exclude the opinions of the
    Plaintiffs’ three experts, Todd H. Hubing, Ph.D., Marthinus van Schoor, Ph.D., and Philip
    Koopman, Ph.D., holding that their opinions were inadmissible under Rule 702 of the
    Federal Rules of Evidence and Daubert v. Merrell Dow Pharmaceuticals, Inc., 
    509 U.S. 579
     (1993). And “the challenged expert opinions [were] critical to the remaining
    summary judgment issues.” Id. at *1. Because the expert opinions failed to prove the
    Plaintiffs’ theory of defect, the theory was “largely hypothetical.” Id. at *2.
    As the district court explained, the Plaintiffs’ “theory is that many predictable
    flaws may occur with the pedal sensors. Plaintiffs theorize that these flawed sensors
    produce faulty voltage signals that should trigger the ETC system’s failsafe modes.
    However, due to a defectively designed ETC system, the failsafe modes are not activated,
    6
    resulting in [UIAs].” Id at *3. Thus, “testing of ETC systems was central to the experts’
    opinions.” Id at *2.
    The district court found that the experts’ “testing was flawed, and Plaintiffs have
    failed to establish other means by which their experts can meet the reliability standard.”
    Id. The district court noted, for example, that the only peer-reviewed publication relied on
    by the experts was a 2015 article by Dr. Hubing; however, the theory relied on in that
    article had been discredited by two federal agencies, the National Highway Traffic Safety
    Administration (“NHTSA”) and the National Aeronautics and Space Administration
    (“NASA”). In analyzing the experts’ testing evidence, the court noted the continuing
    failure of proof establishing any causal link:
    Although Plaintiffs’ experts purport to test [Plaintiffs’ theory of defect],
    they leave a gap between analytical possibility and actual proof of
    occurrence. The experts attempt to excuse this gap by reporting that the
    defect leaves no evidence of its effect. However, this position shifts the
    burden to Ford to prove the negative. Furthermore, there is no “general
    acceptance” within the automotive safety or engineering community that
    underpins Plaintiffs’ theory. The causes of [UIA] are myriad. Some events
    are attributable to driver error, while others are tied to different defects
    from cruise control to mechanical issues. Even though many drivers’
    complaints of [UIA] are credible and likely caused by some defects,
    Plaintiffs’ theory here is still largely hypothetical . . . .
    Id. at *3.
    The district court examined each of the three experts’ individual opinions to
    determine whether that opinion should be admitted into evidence. First, the court rejected
    the opinion of Dr. Hubing 4 whose report was primarily based on the article noted above
    4
    Dr. Hubing is an electrical engineer and a professor at Clemson University.
    7
    and in which he examined five vehicles with ETC systems, including two Ford models, a
    2005 Mustang and a 2006 Explorer. After comparing accelerator pedal performance of
    the five vehicles, Dr. Hubing concluded that “Ford’s Gen II ETC system fails to
    adequately mitigate accelerator pedal faults which can lead to” UIAs. J.A. 10873. In Dr.
    Hubing’s opinion, this was “the most probable reason that Ford vehicles with this throttle
    control system have high reported rates of” UIAs. J.A. 10873.
    The district court found Dr. Hubing’s testing unreliable for two reasons. First, his
    testing required making separate accommodations for the Ford vehicles he tested because
    the testing “was developed to test vehicles with ’two track’ pedal sensors,” but the Ford
    vehicles had “three track” pedal sensors. Johnson, 
    2018 WL 1512377
    , at *4. To
    accommodate this difference, Dr. Hubing arbitrarily assigned a set value to Ford’s third
    pedal without knowing how this affected Ford’s computer source code or software
    program. In some cases, the set value he used for the third track intentionally caused the
    vehicles to accelerate if one of the other two sensors’ values matched this set value.
    Second, Dr. Hubing’s testing rested on questionable assumptions that lacked
    evidentiary foundations. The voltages he injected into the ETC system purportedly
    simulated real-world circumstances and actual vehicle conditions. But the voltage values
    simply reflected Dr. Hubing’s “assumptions of what would happen” if factors such as a
    worn sensor, loose connector, or tin whisker existed. 
    Id.
     at *4 n.6. Furthermore, Dr.
    Hubing’s testing revealed that UIAs occurred when two pedal sensors produced values of
    a certain range, and those values were “close to the same . . . , as though each sensor was
    faulting in the same way.” Id. at *4. But Dr. Hubing did not “offer any testing of sensors
    8
    to verify the assumption that both sensors should be expected to fault and that they do so
    in the same way.” Id.
    The court found that the sources supporting Dr. Hubing’s sensor assumption were
    insufficient to be reliable. Dr. Hubing’s assumption was based on two sources: “first, by
    reference to various documents, such as Ford’s CQIS database (complaints relating to
    either pedal faults and/or [UIA]) and Ford’s design and development phases for the Gen
    II ETC system; second, the inherent knowledge of the expert.” Id. The first source did
    “little” to support Dr. Hubing’s assumption because these documents were “brief,
    and very few reflect[ed] an inspection, testing, or analysis by a trained eye.” Id. As for
    Dr. Hubing’s qualifications, those alone could not substitute for the lack of testing
    evidence.
    The district court found further problems with Dr. Hubing’s report, including that
    “degraded sensors are not the defect, nor are they the only precipitating cause of [UIA],
    according to Plaintiffs’ claim. However, Dr. Hubing’s theory of defect rests significantly
    on the system’s inability to properly recognize and mitigate faulty sensors.” Id. Dr.
    Hubing also had never tested the Plaintiffs’ actual vehicles or attempted to produce
    voltages that would cause a UIA instead of simply injecting these voltages. Finally, the
    NHTSA and NASA in 2011 had rejected his theory as lacking real-world evidence.
    Based on all these findings, the court excluded Dr. Hubing’s opinion.
    Next, the court considered the opinion of Dr. van Schoor who holds a Ph.D. in
    aeronautics and astronautics. He opined that Ford’s accelerator pedal sensors are subject
    to wear or “gunk” buildup, either of which “can lead to failure and erratic vehicle
    9
    behavior.” J.A.10972. The district court found three problems with this theory: (1)
    Plaintiffs’ counsel “explicitly stated that Plaintiffs were not offering his opinion as to a
    defect;” (2) Dr. van Schoor did not perform any inspections or surveys to support his
    theory; and (3) he “did not attribute any of Plaintiffs’ [UIAs] to the problems he
    identified in his report.” Johnson, 
    2018 WL 1512377
    , at *5. Thus, the court found his
    theory irrelevant to the Plaintiffs’ theory of defect.
    Dr. van Schoor also offered an opinion on an alternative vehicle design with BOA,
    but the court did not examine this in depth because the availability of an alternative
    design was not proof of the alleged defect.5 Based on these findings, the court excluded
    Dr. van Schoor’s report.
    The third expert at issue was Dr. Koopman, 6 who opined that a design defect made
    Ford’s Gen II ETC system vulnerable to allowing UIAs. In support, Dr. Koopman tested
    two Ford models, a 2005 Mustang and a 2006 Fusion, by injecting voltages into the
    accelerator wiring harness as a substitute for the three accelerator pedal sensors. Similar
    to Dr. Hubing’s testing, the injected voltages represented the voltages “likely produced
    5
    The district court’s holding is consistent with our precedent. See Sexton By and
    Through Sexton v. Bell Helmets, Inc., 
    926 F.2d 331
    , 338 (4th Cir. 1991) (holding that the
    simple availability of an alternative design at the time of trial “does not lead to the
    conclusion that the design of the [product] was defective”); see also Edwards v. Bell
    Helicopter Textron, Inc., 63 F. App’x 674, 680–81 (4th Cir. 2003) (per curiam)
    (determining that the availability of an alternative design “was irrelevant to the proof” of
    the strict liability and negligent defective design claims because the existence of an
    alternative design could not have contributed to the alleged injury and therefore did not
    establish that an alleged design defect in the product was a proximate cause of the alleged
    injuries).
    6
    Dr. Koopman is a tenured Associate Professor in the Electrical and Computer
    Engineering Department of Carnegie Mellon University.
    10
    by sensors degraded in one or more ways, such as from wear and tear, loose wires, and
    water intrusion.” Johnson, 
    2018 WL 1512377
    , at *5. Next, he evaluated “actual vehicle
    performance” by repeating this testing on a dynamometer 7 that was designed to simulate
    an actual vehicle condition. 
    Id.
     Based on the results of his testing, Dr. Koopman
    concluded that a UIA occurs when two or more sensors produce voltages of a certain
    range close to each other.
    The district court found Dr. Koopman’s approach unreliable for much the same
    reasons that it found Dr. Hubing’s opinion defective. The court noted that he did not test
    or prove his assumption that two or more degraded sensors have produced or would
    produce the voltages he used for his testing. Furthermore, Dr. Koopman purposely chose
    arbitrary voltage inputs that would instruct the system to accelerate. Thus, his “testing
    was an artificial demonstration that essentially mimicked intentional acceleration.” Id. at
    *7, and was not a “realistic example of sensor faults” because it required multiple steps
    “in a sequence that ha[d] no ‘real-world’ support.” Id.
    Furthermore, the district court concluded “Dr. Koopman’s testimony, that
    Plaintiffs’ complaints are consistent with his design defect opinion, is inadequate to tie
    his opinions to this case.” The court explained why this was so:
    First, [Dr. Koopman] relies on nothing more specific than the Consolidated
    Complaint to understand Plaintiffs’ [UIAs]. Second, there are profound
    inconsistencies between the general complaints and his opinions. Nearly
    every Plaintiff described a failure of their brakes to counteract the [UIA],
    7
    Dynamometer is a “device for measuring mechanical force, or power, transmitted
    by a rotating shaft.” Dynamometer, Encyc. Britannica (2018); see Maxwell Dynamometer
    Co. v. United States, 
    386 F.2d 855
    , 859 (Ct. Cl. 1967).
    11
    yet in Dr. Koopman’s own testing procedure, the brakes restrained the
    acceleration. Further, some Plaintiffs reported that their gas pedals were
    moving up and down without a foot-on-pedal, a circumstance not replicated
    in any of the tests done by Plaintiffs’ experts. If these Plaintiffs were right,
    this pedal problem likely would be mechanical, perhaps caused by the
    return spring.
    Id. at *8 (internal citation omitted). Because his testing was not “a reliable basis” for his
    opinions regarding the alleged defect, the district court excluded Dr. Koopman’s opinion.
    Id.
    The district court also found problematic that none of the Plaintiffs’ experts had
    tested or inspected the Plaintiffs’ actual vehicles or attempted to connect their testing to
    any of those vehicles. Instead, the Plaintiffs asserted the alleged ETC defect and experts’
    opinions applied universally to all the thousands of vehicles in their purported class
    despite Drs. Koopman’s and Hubing’s opinions that their testing results varied
    significantly between individual vehicles and that the pedal sensors differed among the
    class vehicles.
    Once the expert opinions were excluded, the district court concluded that the
    Plaintiffs had “no evidence of their core allegation that there is a design defect in Ford’s
    Gen II ETC system.” Id. Insomuch as the Plaintiffs’ theory of defect was without an
    evidentiary basis, they could not establish the existence of a defect and the necessary
    element of causation. Accordingly, the district court granted summary judgment on all
    remaining claims to Ford.
    A group of the Plaintiffs now appeal, and this Court has jurisdiction under 
    28 U.S.C. § 1291
    .
    12
    II.
    A.
    We review summary judgment decisions de novo, see Campbell v. Hewitt,
    Coleman & Assocs., Inc., 
    21 F.3d 52
    , 53 (4th Cir. 1994), and Daubert decisions for abuse
    of discretion, see Nease v. Ford Motor Co., 
    848 F.3d 219
    , 228 (4th Cir. 2017). A district
    court abuses its discretion if it makes an error of law or clearly erroneous factual finding.
    See id. at 228.
    The merits of the district court’s Daubert decision addressing the Plaintiffs’ proof
    of their defect theory is our initial focus because their entire case hinges on the allegedly
    defective ETC system as the cause of UIAs. UIAs alone do not substantiate their theory
    because, as the Plaintiffs concede on appeal, many factors unrelated to an ETC system
    could trigger UIAs. See, e.g., Opening Br. 31 (“[M]ultiple circumstances can initiate
    unintended acceleration signals.”). Thus, to establish the existence of the alleged defect
    and the requisite causal link between it and their UIAs, the Plaintiffs proffered the
    opinions of the three experts, Drs. Hubing, van Schoor, and Koopman. As the district
    court recognized, these experts’ opinions are “critical” to the Plaintiffs’ case because
    their theory of defect is “largely hypothetical” without them. Johnson, 
    2018 WL 1512377
    , at *3. Accordingly, if the district court correctly excluded the expert opinions,
    the Plaintiffs’ case fails because they would be “unable to prove the fundamental theory
    of their case.” Id. at *9.
    B.
    13
    The district court excluded the expert opinions under the Supreme Court’s
    landmark precedent in Daubert, which established that under the Federal Rules of
    Evidence “the admissibility of scientific evidence no longer was limited to knowledge or
    evidence ‘generally accepted’ as reliable in the relevant scientific community.” Nease,
    848 F.3d at 228 (citing Daubert, 
    509 U.S. at
    588–89). Instead, Daubert held that courts
    must evaluate proposed expert testimony according to Rule 702, which tasks a district
    judge with “ensuring that an expert’s testimony both rests on a reliable foundation and is
    relevant to the task at hand.” 
    509 U.S. at 597
    . This rule requires trial judges to conduct “a
    preliminary assessment of whether the reasoning or methodology underlying the
    testimony is scientifically valid and of whether that reasoning or methodology properly
    can be applied to the facts in issue. . . . . Many factors will bear on the inquiry, and we do
    not presume to set out a definitive checklist or test.” 
    Id.
     at 592–93.
    Under Rule 702, an expert’s testimony is relevant if it has “a valid scientific
    connection to the pertinent inquiry.” 
    Id. at 592
    . To be reliable, the testimony “must be
    based on scientific, technical, or other specialized knowledge and not on belief or
    speculation, and inferences must be derived using scientific or other valid methods.”
    Oglesby v. Gen. Motors Corp., 
    190 F.3d 244
    , 250 (4th Cir. 1999) (citing Daubert, 
    509 U.S. at 590
    , 592–93).
    In determining whether expert testimony is “sufficiently reliable to be admissible,”
    a district court generally considers several factors:
    First, “a key question to be answered in determining whether a theory or
    technique is scientific knowledge that will assist the trier of fact will be
    whether it can be (and has been) tested.” A second question . . . is “whether
    14
    the theory or technique has been subjected to peer review and
    publication.” Publication regarding the theory bears upon peer review; “the
    fact of publication (or lack thereof) in a peer reviewed journal will be a
    relevant, though not dispositive, consideration in assessing the scientific
    validity of a particular technique or methodology on which an opinion is
    premised.” Third, “in the case of a particular scientific technique, the court
    ordinarily should consider the known or potential rate of error.” Fourth, . . .
    “‘general acceptance’” is . . . relevant to the reliability inquiry.
    “Widespread acceptance can be an important factor in ruling particular
    evidence admissible, and a known technique which has been able to attract
    only minimal support with the community may properly be viewed with
    skepticism.”
    Nease, 848 F.3d at 229 (quoting Daubert, 
    509 U.S. at
    593–94) (internal citations and
    alterations omitted).
    This list, however, is “not exhaustive,” and “‘neither necessarily nor exclusively
    applies to all experts or in every case.’” 
    Id.
     (quoting Kumho Tire Co. v. Carmichael, 
    526 U.S. 137
    , 141 (1999)). “[A]t bottom, the court’s evaluation is always a flexible one, and
    the court’s conclusions necessarily amount to an exercise of broad discretion guided by
    the overarching criteria of relevance and reliability.” Oglesby, 190 F.3d at 250. Thus, the
    trial court has “broad latitude” in determining whether “Daubert’s specific factors are, or
    are not, reasonable measures of reliability in a particular case.” Kumho Tire, 
    526 U.S. at 153
    . Here, the district court properly considered appropriate factors and did not abuse its
    discretion in excluding the experts’ opinions based on their lack of relevance and
    reliability.
    C.
    The Plaintiffs fail to show that the district court made “a clearly erroneous factual
    finding” or “error of law” by excluding their expert witnesses. See Nease, 848 F.3d at
    15
    228. They argue that the district court did not consider certain Daubert factors, such as
    the known or potential rate of error, or considered Daubert factors, like peer review, in an
    inappropriate manner. This argument lacks merit, in part, because the Plaintiffs do not
    identify a tangible error in the district court’s analysis. The district court was not under
    any obligation to consider a certain factor or weigh factors it did consider in a particular
    manner. See id. at 229. As noted earlier, the trial court’s inquiry is a “flexible one,” and it
    exercises “broad discretion” in choosing which Daubert factors to apply and how to
    consider them. Oglesby, 190 F.3d at 250; accord Nease, 848 F.3d at 229.
    The Plaintiffs further argue that the court made conclusory findings and wrongly
    assessed the expert opinions. We disagree. Contrary to the Plaintiffs’ assertion, our
    review shows that the district court thoroughly reviewed the record, including the
    experts’ reports and the depositions of these experts, to understand their testing, theories,
    and methodologies. The court then provided a well-reasoned analysis of the experts’
    theories and testing based on its consideration of relevant Daubert factors such as general
    acceptance of a theory within a relevant field, peer review, and the scientific validity of
    their underlying methodologies.
    For example, the district court properly noted that Dr. Hubing’s testing method
    was, at a minimum, suspect because it had been rejected by NASA and NHTSA. Further,
    as the court pointed out, Dr. Hubing never tested any vehicle in actual conditions so all
    his projections were purely theoretical. His “testing,” at least in part, seemed artificially
    induced to produce a desired result and did not reflect real-world results from any vehicle
    claiming a UIA. In sum, Dr. Hubing’s opinion was partly ipse dixit.
    16
    As for Dr. van Schoor, even without examining the merits of his testimony, the
    Plaintiffs effectively pled him out of the case. During the district court proceedings, the
    Plaintiffs stipulated “on the record that Dr. van Schoor will not offer defect opinions per
    se.” J.A. 11934. Even more to the point, Plaintiffs’ counsel admitted Dr. van Schoor
    failed to meet the necessary threshold of evidentiary reliability: “candidly I will concede
    to the Court that he couches all of his conclusions in the form of a defect opinion.
    Candidly I’ll say to the Court that I don’t know that Dr. van Schoor in this case tested his
    opinions against the rigor that is required for Federal Rules of Evidence.” J.A. 11932.
    Regardless, we find no abuse of discretion in the district court’s merits analysis of
    Dr. van Schoor’s testimony for the reasons it explained. We simply note two salient
    points from that analysis: Dr. van Schoor “performed no inspections nor surveys to
    support his theory about contacting sensors” and “did not attribute any of Plaintiffs’
    [UIAs] to the problems he identified in his report.” Johnson, 
    2018 WL 1512377
    , at *5.
    Dr. Koopman’s testimony fares no better. As with the other experts, there is a
    considerable gap between Dr. Koopman’s theory and any evidentiary proof of causation
    related to an ETC defect and a UIA. The district court aptly recited the evidentiary failure
    on Dr. Koopman’s part:
    Dr. Koopman admits that in many of his tests, he injected faults with
    voltages designed to produce pedal angles consistent with acceleration.
    . . . Yet, nowhere does he validate his hypothesis that degraded
    sensors, presumably to be expected, will actually cause or, in fact, have
    produced faulty voltages in the way he arranged for his testing. . . . The
    testing was an artificial demonstration that essentially mimicked intentional
    acceleration. Dr. Koopman offers no testing of Plaintiffs’ vehicles, or the
    exemplars he chose, to demonstrate how degraded sensors or the other
    17
    circumstances can produce similar voltages that result in unintended open
    throttle.
    Id. at *7 (internal citation omitted).
    Further, the district court correctly observed that none of the experts tested any of
    the Plaintiffs’ vehicles or any of the thousands of Ford vehicles in their purported class
    which they allege had a UIA. Of the multitude of vehicles the Plaintiffs claim to be
    defective, the record does not reflect they attempted to test even one vehicle purported to
    have had a UIA, much less conduct such a test under real-world conditions. Most
    importantly, none of the proffered expert opinions purport to tie their testing to any
    alleged UIA so as to show the fundamental element of causation. To the contrary, the
    Plaintiffs’ experts disclaimed any finding or opinion as to the causation of any specific
    UIA. J.A. 1754 ([Counsel’s question to Dr. Hubing:] “But you can’t say that your
    vulnerabilities that you identify actually cause the event in the plaintiffs’ vehicles,
    correct? . . . [Answer:] In any one of those vehicles, no.”); J.A. 10196–97 ([Counsel’s
    question to Dr. van Schoor:] “Have you identified any alleged unwanted acceleration
    event occurring in a Ford vehicle that you have determined resulted from any of the
    alleged defects or vulnerabilities that you have identified in your report? [Answer:] I have
    not.”); see also J.A. 8922–23 ([Counsel’s question to Dr. Koopman:]“And then you don’t
    go out to the vehicle to see if there are any other possible causes or explanation for their
    claim; correct? . . . [Answer:] I have not physically examined the vehicles.”); J.A. 8925–
    26 ([Dr. Koopman:] “What I am saying is that I see explanations consistent with software
    18
    and hardware defects, and I see that that’s consistent with my report. That’s all I have
    been saying.”). 8
    The court’s well-articulated analysis clearly distinguishes this case from Nease in
    which the district court failed to act as a gatekeeper by not assessing the expert’s
    reliability but leaving that question to the jury. See 848 F.3d at 231. Instead, the court
    here faithfully performed its duty as a “gatekeeper” in the manner we approved in In re
    Lipitor (Atorvastatin Calcium) Marketing, Sales Practices and Products Liability
    Litigation (No II) MDL 2502, 
    892 F.3d 624
    , 631 (4th Cir. 2018). There, we upheld the
    district court’s extensive analysis of the experts’ theories and testing, which formed the
    basis of the court’s exclusion of several expert opinions, because that court, like the
    district court here, properly “identified and articulated clear . . . concerns it had about the
    manner in which [the expert] reached his conclusions.” 
    Id. at 638
    . In approving the
    district court’s analysis in In re Lipitor, we once more emphasized that “‘[m]any factors
    will bear on the inquiry,’ and there is no ‘definitive checklist or test.’” 
    Id. at 637
     (quoting
    Daubert, 
    509 U.S. at 593
    ).
    Having failed on their primary arguments, the Plaintiffs argue that the district
    court mischaracterizes the experts’ testimony during depositions, but this argument
    8
    The district court found, as do we, the anomaly of the Plaintiffs’ theory at trial
    that the ETC defect was universal to all the class vehicles, but that their experts own
    laboratory testing showed significant differences between vehicles. As the district court
    noted, “Dr. Hubing’s testing revealed significant differences between the two Ford
    vehicles, which he asserts had identical ETC systems,” and yet, the Plaintiffs are
    “inconsistent” because they “maintain the Gen II ETC system used by Ford is exactly the
    same in all vehicles, but then they excuse results when it is not.” Johnson, 
    2018 WL 1512377
    , at *8.
    19
    simply channels the Plaintiffs’ disagreement with the district court’s findings. The
    Plaintiffs essentially assert the district court erred by making findings that were favorable
    to Ford or reaching conclusions that contradicted their portrayal of the expert opinions.
    For instance, the Plaintiffs challenge the district court’s finding that when Dr. Hubing
    was asked whether “he ever saw ‘dual faults occur in the same resistive ranges’ in the
    ‘real world,’ [he] ultimately answered no.” Johnson, 
    2018 WL 1512377
    , at *4. They
    assert that this finding is erroneous because Dr. Hubing answered “no” to an entirely
    different question. Our review of the record reveals that the district court’s finding is
    correct. When Ford’s counsel asked Dr. Hubing whether he had ever “physically see[n] . .
    . dual faults occur in the same resistive range,” he answered, “. . . how would we do
    that?” because “physical evidence of two simultaneous faults occurring [in the real
    world] . . . would be basically impossible to find.” J.A. 09335–36. Similarly, the
    Plaintiffs’ other arguments related to the district court’s alleged mischaracterization
    reveal no more than their disagreement with the district court’s findings or contrary
    interpretation, and do not show that the court committed any error.
    Once the opinions of the three experts were excluded, the district court necessarily
    concluded that the Plaintiffs had “no evidence of their core allegation that there is a
    design defect in Ford’s Gen II ETC system.” Johnson, 
    2018 WL 1512377
    , at *8. As the
    court held, other evidence that the Plaintiffs recite, such as a software expert’s opinion
    and Ford’s internal documents, does not prove their defect theory.
    The Plaintiffs point to unverified reports of UIAs from Ford vehicle drivers, but,
    as noted above, UIA alone does not prove the existence of a defect. Similarly, the
    20
    availability of an alternative vehicle design with BOA does not substantiate the Plaintiffs’
    theory of defect because the alternative design’s mere availability does not prove that the
    existing design is defective or could lead to a UIA. See Sexton, 
    926 F.2d at
    337–38
    (remanding for new trial where district court improperly allowed expert testimony of a
    possible alternative design to substitute for evidence that was necessary to satisfy
    plaintiff’s burden of showing a design defect); Edwards, 63 F. App’x at 680–81
    (discussing the difference between the two types of evidence). The Plaintiffs further
    direct our attention to Ford’s internal documents without discussing what these
    documents specifically contain or how they prove the missing element of causation.
    Instead, they generally argue that “the factual record in this case is rife with internal
    documents demonstrating Ford’s knowledge of the defect.” Reply Br. 14. Like the
    Plaintiffs’ other evidence, this generalized argument neither proves nor disproves their
    theory of defect. Lastly, the Plaintiffs focus on the opinion of the software expert, Steve
    Loudon, but the district court could not have considered this opinion because the
    Plaintiffs admit that it was not available to the court and is not in the record. Thus, we
    agree with the district court that after the expert opinions were excluded, the Plaintiffs
    had no proof of a defect in Ford’s ETC system.
    21
    Because the Plaintiffs could not prove their theory of defect and thus fail to meet
    the essential element of causation, we affirm the district court’s grant of summary
    judgment on all claims to Ford. 9
    III.
    For the foregoing reasons, the district court’s Daubert and summary judgment
    decisions are
    AFFIRMED.
    9
    We find it unnecessary to assess the merits of the Plaintiffs’ claims dismissed
    under Federal Rule of Civil Procedure 12(b)(6) because those claims are based on the
    same unsubstantiated theory and suffer from the same lack of proof, although the district
    court dismissed them for additional reasons not discussed here. Thus, even if those claims
    had survived the Rule 12(b)(6) challenge, they would not have survived the district
    court’s summary judgment rulings because all contain the same failure of proof.
    Similarly, we find without merit the Plaintiffs’ argument that the district court
    erred by granting summary judgment to Ford on their various state consumer protection
    claims because those claims also fail for the reasons stated herein. The Plaintiffs argue
    the court did not recognize that those claims simply require “the breach of a duty to warn
    consumers of a known risk or danger or violation of a prohibition against misleading the
    consumer.” Opening Br. 37. The Plaintiffs cannot establish the existence of a defect, let
    alone its risk or danger. Ford does not have a duty to warn consumers of an unproven risk
    or danger associated with a hypothetical and unproven defect.
    22