                                            PRECEDENTIAL

       UNITED STATES COURT OF APPEALS
            FOR THE THIRD CIRCUIT
                 ___________

                      No. 12-2621
                      ___________

            GABRIEL JOSEPH CARRERA,
   on behalf of himself and all others similarly situated

                             v.

              BAYER CORPORATION;
            BAYER HEALTHCARE, LLC.,
                            Appellants

 *(Amended Pursuant to the Clerk‟s Order of July 5, 2012)

               _______________________

            On Appeal from the District Court
              for the District of New Jersey
             D.C. Civil No. 2-08-cv-04716
               (Honorable Jose L. Linares)
                     ______________

                  Argued April 16, 2013

Before: SCIRICA, SMITH and CHAGARES, Circuit Judges

                 (Filed: August 21, 2013)
Matthew R. Ford, Esq.
Christopher D. Landgraff, Esq.
Rebecca Weinstein Bacon, Esq. [ARGUED]
Bartlit, Beck, Herman, Palenchar & Scott
54 West Hubbard Street
Room 300
Chicago, IL 60654

      Counsel for Appellants

Caroline F. Bartlett, Esq.
James E. Cecchi, Esq.
Lindsey H. Taylor, Esq.
Carella, Byrne, Cecchi, Olstein, Brody & Agnello
5 Becker Farm Road
Roseland, NJ 07068

Joe R. Whatley, Jr., Esq. [ARGUED]
Whatley, Drake & Kallas
1540 Broadway
37th Floor
New York, NY 10036

      Counsel for Appellee

John Beisner, Esq.
Skaden, Arps, Slate, Meagher & Flom
1440 New York Avenue, N.W.
Washington, DC 20005

      Counsel for Amicus Curiae

                   _________________




                               2
                OPINION OF THE COURT
                   _________________

SCIRICA, Circuit Judge.

              In this Fed. R. Civ. P. 23(f) appeal, Bayer
      Corporation and Bayer Healthcare contest the
      certification of a class of consumers who purchased
      Bayer‟s One-A-Day WeightSmart diet supplement in
      Florida. The sole issue on appeal is whether the class
      members are ascertainable. While this interlocutory
      appeal was pending, we decided Marcus v. BMW of
      North America, LLC, in which we held “[i]f class
      members are impossible to identify without extensive
      and individualized fact-finding or „mini-trials,‟ then a
      class action is inappropriate.” 687 F.3d 583, 593 (3d
      Cir. 2012). We explained that if class members cannot
      be ascertained from a defendant‟s records, there must
      be “a reliable, administratively feasible alternative,”
      but we cautioned “against approving a method that
      would amount to no more than ascertaining by
      potential class members‟ say so.” Id. at 594. In light of
      Marcus, we will vacate the class certification order and
      remand.

                              I.

       Gabriel Carrera brings this class action against Bayer
Corporation and Bayer Healthcare, LLC (“Bayer”), claiming
that Bayer falsely and deceptively advertised its product One-
A-Day WeightSmart. WeightSmart was promoted as a
multivitamin and dietary supplement that had metabolism-




                              3
enhancing effects. The recommended daily dose was one
tablet and prices ranged from about $8.99 for fifty tablets to
about $16.99 for one hundred tablets. Bayer sold
WeightSmart in retail stores, such as CVS, until January
2007. Bayer did not sell it directly to consumers. Carrera
alleges Bayer falsely claimed that WeightSmart enhanced
metabolism by its inclusion of epigallocatechin gallate, a
green tea extract.

       Carrera initially sought to certify a nationwide class
under Fed. R. Civ. P. 23(b)(3) bringing a claim under the
New Jersey Consumer Fraud Act, as Bayer‟s headquarters is
in New Jersey. The court denied certification, concluding that
New Jersey law did not apply to out-of-state customers. This
order is not before us on appeal.

        Carrera then moved to certify a Rule 23(b)(3) class of
Florida consumers under the Florida Deceptive and Unfair
Trade Practices Act. One of Bayer‟s challenges to
certification, and the issue on this appeal, is whether the class
members are ascertainable. In this case, there is no dispute
that class members are unlikely to have documentary proof of
purchase, such as packaging or receipts. And Bayer has no
list of purchasers because, as noted, it did not sell
WeightSmart directly to consumers.

       Carrera advanced two ways to ascertain the class: first,
by retailer records of online sales and sales made with store
loyalty or rewards cards; second, by affidavits of class
members, attesting they purchased WeightSmart and stating
the amount they purchased. Bayer challenged this latter
method on the ground that memories of putative class
members will be unreliable. Bayer argued that, in Carrera‟s




                               4
own deposition testimony, he failed to remember when he
purchased WeightSmart and that he confused it with
WeightSmart Advanced and other generic or similar products
(none of which are part of this litigation). In response, Carrera
produced a declaration of James Prutsman, who works for a
company that verifies and processes class settlement claims,
in which Prutsman stated there are ways to verify the types of
affidavits at issue here and screen out fraudulent claims.

       The court certified the class, defined as all persons
who purchased WeightSmart in Florida.1 It characterized the
issue of ascertainability as one of manageability, stating
“„speculative problems with case management‟” are
insufficient to prevent class certification. Carrera v. Bayer
Corp., Civ. A. No. 08-4716, 2011 WL 5878376, at *4 (D.N.J.
Nov. 22, 2011) (quoting Klay v. Humana, Inc., 382 F.3d
1241, 1272-73 (11th Cir. 2004)). The court concluded Carrera
had satisfied his burden, noting “that the claims involved will
be relatively small and Plaintiff points to methods to verify
claims.” Id. Bayer appealed. It contends Carrera has failed to
demonstrate the class is ascertainable because there is no
evidence that any retailer records show who purchased
WeightSmart. Bayer also argues that the use of unverifiable
affidavits to ascertain class members fails to comply with
Rule 23 and violates its rights under the due process clause.

                               II.

       The District Court had jurisdiction under 28 U.S.C. §

1
  The class definition does not include a class period. Bayer
sold WeightSmart from December 2003 through January
2007.




                               5
1332(d). We have jurisdiction under 28 U.S.C. § 1292(e) and
Fed. R. Civ. P. 23(f). “We review a class certification order
for abuse of discretion, which occurs if the district court‟s
decision rests upon a clearly erroneous finding of fact, an
errant conclusion of law or an improper application of law to
fact.” In re Hydrogen Peroxide Antitrust Litig., 552 F.3d 305,
312 (3d Cir. 2008) (quotation omitted). “Whether an incorrect
legal standard has been used is an issue of law to be reviewed
de novo.” Id. (quotation omitted).

                             III.

        In Marcus, we explained the concept of
ascertainability at length for the first time. 687 F.3d at 592-
95. The claim in Marcus was that Bridgestone run-flat tires
(“RFTs”) were defective because they were highly
susceptible to flats; could only be replaced, not repaired; and
were highly priced. Id. at 588. The district court certified a
Rule 23(b)(3) class consisting of “any and all current and
former owners and lessees of 2006, 2007, 2008, and 2009
BMW vehicles equipped with run-flat tires manufactured by
Bridgestone . . . and sold or leased in New Jersey whose Tires
have gone flat and been replaced.” Id. at 590 (quotation and
alterations omitted). The defendants appealed, and we vacated
the order certifying the class.

       Before turning to the explicit requirements of Rule 23
in Marcus, we addressed two “preliminary matters”: first,
whether the class was clearly defined, and second, “whether
the class must be (and, if so, is in fact) objectively
ascertainable.” Id. at 591. We concluded the class was not
clearly defined. At the least, the definition of the class was
broader than intended and did not define the claims, issues, or




                              6
defenses to be treated on a class-wide basis. Id. at 592.
Accordingly, we remanded the case for clarification of the
class definition.

        We then addressed ascertainability. We began by
stating, “[m]any courts and commentators have recognized
that an essential prerequisite of a class action, at least with
respect to actions under Rule 23(b)(3), is that the class must
be currently and readily ascertainable based on objective
criteria.” Id. at 592-93 (citing cases). “If class members are
impossible to identify without extensive and individualized
fact-finding or „mini-trials,‟ then a class action is
inappropriate.” Id. at 593. We noted, “[s]ome courts have
held that where nothing in company databases shows or could
show whether individuals should be included in the proposed
class, the class definition fails.” Id. (citing cases).

       We then explained the

       ascertainability requirement serves several
       important objectives. First, it eliminates serious
       administrative burdens that are incongruous
       with the efficiencies expected in a class action
       by insisting on the easy identification of class
       members. Second, it protects absent class
       members by facilitating the best notice
       practicable under Rule 23(c)(2) in a Rule
       23(b)(3) action. Third, it protects defendants by
       ensuring that those persons who will be bound
       by the final judgment are clearly identifiable.

Id. (citations and quotations omitted).




                               7
       We set forth why the “proposed class action raise[d]
serious ascertainability issues.” Id. Defendant BMW
explained that it could not determine by its records which
vehicles fit the definition of the class because it did not keep
records of which cars got fitted with Bridgestone RFTs,
because some customers may have changed tires (of which
BWM had no record), and because BMW would not have
known which customers experienced flat tires. Id. at 593-94.
We stated that if plaintiff were to attempt to re-certify a class
on remand, the court “must resolve the critical issue of
whether the defendants‟ records can ascertain class members
and, if not, whether there is a reliable, administratively
feasible alternative.” Id. at 594. We cautioned “against
approving a method that would amount to no more than
ascertaining by potential class members‟ say so. For example,
simply having potential class members submit affidavits that
their Bridgestone RFTs have gone flat and been replaced may
not be proper or just.” Id. (quotation omitted). “Forcing
BMW and Bridgestone to accept as true absent persons‟
declarations that they are members of the class, without
further indicia of reliability, would have serious due process
implications.” Id.

                                IV.

                                A.

        “A party seeking class certification must affirmatively
demonstrate his compliance with” Rule 23. Wal-Mart Stores,
Inc. v. Dukes, 131 S. Ct. 2541, 2551 (2011). “Class
certification is proper only „if the trial court is satisfied, after
a rigorous analysis, that the prerequisites‟ of Rule 23 are
met.” Hydrogen Peroxide, 552 F.3d at 309 (quoting Gen. Tel.




                                 8
Co. of Sw. v. Falcon, 457 U.S. 147, 161 (1982)). “Frequently
that „rigorous analysis‟ will entail some overlap with the
merits of the plaintiff‟s underlying claim. That cannot be
helped. „[T]he class determination generally involves
considerations that are enmeshed in the factual and legal
issues comprising the plaintiff‟s cause of action.‟” Dukes, 131
S. Ct. at 2551-52 (alteration in original) (quoting Falcon, 457
U.S. at 160). “Factual determinations necessary to make Rule
23 findings must be made by a preponderance of the
evidence.” Hydrogen Peroxide, 552 F.3d at 320.

        These same standards apply to the question of
ascertainability. Class ascertainability is “an essential
prerequisite of a class action, at least with respect to actions
under Rule 23(b)(3).” Marcus, 687 F.3d at 592-93. “[T]here
is „no reason to doubt‟” that the “rigorous analysis”
requirement “„applies with equal force to all Rule 23
requirements.‟” Hydrogen Peroxide, 552 F.3d at 309 n.5
(quoting In re Initial Pub. Offering Sec. Litig., 471 F.3d 24,
33 n.3 (2d Cir. 2006)). Accordingly, a plaintiff must show, by
a preponderance of the evidence, that the class is “currently
and readily ascertainable based on objective criteria,”
Marcus, 687 F.3d at 593, and a trial court must undertake a
rigorous analysis of the evidence to determine if the standard
is met.
        “A party‟s assurance to the court that it intends or
plans to meet the requirements [of Rule 23] is insufficient.”
Hydrogen Peroxide, 552 F.3d at 318. A plaintiff may not
merely propose a method of ascertaining a class without any
evidentiary support that the method will be successful. “„A
critical need‟” of the trial court at certification “„is to
determine how the case will be tried,‟” id. at 319 (quoting
Fed. R. Civ. P. 23 advisory committee‟s note, 2003




                               9
Amendments), including how the class is to be ascertained.

                               B.

       Ascertainability mandates a rigorous approach at the
outset because of the key roles it plays as part of a Rule
23(b)(3) class action lawsuit. First, at the commencement of a
class action, ascertainability and a clear class definition allow
potential class members to identify themselves for purposes
of opting out of a class. Second, it ensures that a defendant‟s
rights are protected by the class action mechanism. Third, it
ensures that the parties can identify class members in a
manner consistent with the efficiencies of a class action.

       “„[T]he class-action device saves the resources of both
the courts and the parties by permitting an issue potentially
affecting every [class member] to be litigated in an
economical fashion under Rule 23.‟” Falcon, 457 U.S. at 155
(second alteration in original) (quoting Califano v. Yamasaki,
442 U.S. 682, 701 (1979)). If a class cannot be ascertained in
an economical and “administratively feasible” manner,
Marcus, 687 F.3d at 594, significant benefits of a class action
are lost. See id. at 593 (explaining ascertainability “eliminates
serious administrative burdens that are incongruous with the
efficiencies expected in a class action” (quotation omitted)).
Accordingly, a trial court should ensure that class members
can be identified “without extensive and individualized fact-
finding or „mini-trials,‟” id., a determination which must be
made at the class certification stage.

       In this case, the ascertainability question is whether
each class member purchased WeightSmart in Florida. If this
were an individual claim, a plaintiff would have to prove at




                               10
trial he purchased WeightSmart. A defendant in a class action
has a due process right to raise individual challenges and
defenses to claims, and a class action cannot be certified in a
way that eviscerates this right or masks individual issues. See
McLaughlin v. Am. Tobacco Co., 522 F.3d 215, 231-32 (2d
Cir. 2008) (rejecting a “fluid recovery” method of
determining individual damages, in which aggregate damages
would be based on estimates of the number of defrauded class
members and their average loss), abrogated on other grounds
by Bridge v. Phoenix Bond & Indem. Co., 553 U.S. 639
(2008); see also Dukes, 131 S. Ct. at 2561 (rejecting a method
of class certification in which a sample set of class members
would be used to extrapolate average damages). A defendant
has a similar, if not the same, due process right to challenge
the proof used to demonstrate class membership as it does to
challenge the elements of a plaintiff‟s claim. See Marcus, 687
F.3d at 594 (“Forcing BMW and Bridgestone to accept as true
absent persons‟ declarations that they are members of the
class, without further indicia of reliability, would have serious
due process implications.”). Ascertainability provides due
process by requiring that a defendant be able to test the
reliability of the evidence submitted to prove class
membership.

        The method of determining whether someone is in the
class must be “administratively feasible.” Id. A plaintiff does
not satisfy the ascertainability requirement if individualized
fact-finding or mini-trials will be required to prove class
membership. Id. at 593. “Administrative feasibility means
that identifying class members is a manageable process that
does not require much, if any, individual factual inquiry.”
William B. Rubenstein & Alba Conte, Newberg on Class
Actions § 3:3 (5th ed. 2011); see also Bakalar v. Vavra, 237




                               11
F.R.D. 59, 64 (S.D.N.Y. 2006) (“Class membership must be
readily identifiable such that a court can determine who is in
the class and bound by its ruling without engaging in
numerous fact-intensive inquiries.”).

        The type of challenge to the reliability of evidence that
is required will vary based on the nature of the evidence. For
example, if Carrera produces retailer records that purport to
list purchasers of WeightSmart, Bayer can challenge the
reliability of those records, perhaps by deposing a corporate
record-keeper.2 In sum, to satisfy ascertainability as it relates
to proof of class membership, the plaintiff must demonstrate
his purported method for ascertaining class members is
reliable and administratively feasible, and permits a defendant
to challenge the evidence used to prove class membership.

                               V.

       Carrera contends the class is ascertainable. He points
to two types of evidence that can be used to determine who is
a class member. First, he argues the class can use records
from retailers, which purportedly track customers who make
purchases online or who use loyalty cards. Second, he
proposes using affidavits of class members attesting to their
purchases of WeightSmart. We conclude that, based on the
evidence produced below, neither method satisfies Carrera‟s
burden to show the class is ascertainable.

2
  Although some evidence used to satisfy ascertainability,
such as corporate records, will actually identify class
members at the certification stage, ascertainability only
requires the plaintiff to show that class members can be
identified.




                               12
                              A.

       Carrera argues he will be able to show class
membership using retailer‟s records of sales made with
loyalty cards, e.g., CVS ExtraCare cards,3 and records of
online sales. Carrera points to a Federal Trade Commission
(FTC) settlement with CVS regarding the sale of a
supplement that was falsely advertised as boosting immune
systems. The supplement was sold only at CVS. The FTC
stated in its press release regarding the settlement that
“[p]urchasers will be identified through the CVS ExtraCare
card program and sales on cvs.com.” A1089.

        Bayer contends there is no evidence that any other
retailer of WeightSmart has membership cards, that the FTC
case is inapposite as it was a stipulated settlement in a non-
Rule 23 context,4 in which some of the money paid might go
to class members but did not have to, and that it is speculative
whether CVS or any other retailer‟s records will reveal
customers who purchased WeightSmart.

      The evidence put forth by Carrera is insufficient to
show that retailer records in this case can be used to identify

3
  ExtraCare cards are membership cards that offer customers
discounts. A1091.
4
   Settlement classes raise different certification issues than
litigation classes. See Amchem Prods., Inc. v. Windsor, 521
U.S. 591, 620 (1997). Accordingly, we question whether the
FTC‟s proposals for identifying purchasers, made as part of a
settlement (and a non-class action settlement at that), bear any
relevance to the issue of ascertainability in this case.




                              13
class members. Depending on the facts of a case, retailer
records may be a perfectly acceptable method of proving
class membership. But there is no evidence that a single
purchaser of WeightSmart could be identified using records
of customer membership cards or records of online sales.
There is no evidence that retailers even have records for the
relevant period. The FTC‟s press release does not support a
finding that these records can determine class membership on
the facts of this case. Moreover, we have no evidence the
FTC‟s method was successful.

                               B.

        Carrera also contends the class is ascertainable using
affidavits of class members. He advances three arguments.
First, due to the low value of the claims, class members will
be unlikely to submit fraudulent affidavits. Second, because
Bayer‟s total liability will not depend on the reliability of the
affidavits, the ascertainability requirement should be relaxed.
Finally, a screening method such as the one described in the
Prutsman Declaration will ensure any unreliable affidavits are
identified and disregarded.

                               1.

        Because the claims are of low value, Carrera argues it
is less likely someone would fabricate a claim. He concedes it
is unlikely customers would have retained a receipt, but
asserts this is irrelevant to possible falsification. He contrasts
the claims at issue here to those in Marcus, which involved
more money and more complicated issues of fact as to
whether an individual was a class member.




                               14
       This argument fails because it does not address a core
concern of ascertainability: that a defendant must be able to
challenge class membership. This is especially true where the
named plaintiff‟s deposition testimony suggested that
individuals will have difficulty accurately recalling their
purchases of WeightSmart.5 Cf. In re Phenylpropanolamine
(PPA) Prods. Liab. Litig., 214 F.R.D. 614, 618-19 (W.D. Wa.
2003) (concluding affidavits could not be used to ascertain a
class because the named plaintiffs had difficulty remembering
the products they bought that contained PPA).

                               2.

        Carrera also argues ascertainability is less important in
this case because Bayer‟s total liability will be determined at
trial, and will not increase or decrease based on the affidavits
submitted. As noted, this is an action under the Florida
Deceptive and Unfair Trade Practices Act (FDUTPA), Fla.
Stat. § 501.201 et seq. “[A] consumer claim for damages
under FDUTPA has three elements: (1) a deceptive act or
unfair practice; (2) causation; and (3) actual damages.”
Rollins, Inc. v. Butland, 951 So. 2d 860, 869 (Fla. Dist. Ct.
App. 2006). There is no requirement of actual reliance on the
deceptive act. See Fitzpatrick v. Gen. Mills, Inc., 635 F.3d
1279, 1282-83 (11th Cir. 2011) (citing Davis v. Powertel,
Inc., 776 So. 2d 971, 973 (Fla. Dist. Ct. App. 2000)). “[T]he
question is not whether the plaintiff actually relied on the
alleged deceptive trade practice, but whether the practice was

5
  As mentioned, in his deposition testimony, Carrera was
unable to remember when he purchased WeightSmart and
confused WeightSmart with other products that are not part of
this litigation.




                               15
likely to deceive a consumer acting reasonably in the same
circumstances.” Davis, 776 So. 2d at 974.

        Contending liability under the FDUTPA is not based
on individual issues, Carrera argues that he can prove at trial
that Bayer owes a refund for every purchase of
WeightSmart.6 Since Bayer‟s records show it sold
approximately $14 million worth of WeightSmart in Florida,
Carrera asserts Bayer‟s liability will be determined at trial to
be $14 million—no more, no less. As a result, affidavits
attesting to class membership will only be used to determine
to whom to pay the refund, and in what amount.

       Under no circumstances, Carrera assures us, will Bayer
pay any amount other than $14 million, even if a significant
number of inaccurate claims are submitted and paid out. For
example, if claims are made for more than $14 million, and
inaccurate or false claims cannot be screened out, claimants
will simply receive less than they are entitled to. And if too
few claims are made, Carrera asserts the excess funds will not
be returned to Bayer but will go to an unclaimed property
fund. Carrera contrasts this situation with Marcus. In Marcus,
there was no evidence of the total number of RFTs allegedly
purchased in violation of the consumer protection laws.
Accordingly, each claim submitted would have increased the
amount of money the defendants would have had to pay. As a

6
  Bayer argues that if it is liable, its liability will be limited to
refunding the premium consumers paid for WeightSmart
based on its metabolism-enhancing claims. For purposes of
this appeal, it makes no difference whether customers would
be entitled to a full refund or merely a refund of this
premium.




                                 16
result, the defendants had a more substantial interest in
screening out false claims. Because Bayer‟s total liability
cannot be so affected by unreliable affidavits, Carrera argues
Bayer lacks an interest in challenging class membership.

       Under Carrera‟s view, if fraudulent or inaccurate
claims are paid out, the only harm is to other class members.
But ascertainability protects absent class members as well as
defendants, Marcus, 687 F.3d at 593, so Carrera‟s focus on
Bayer alone is misplaced. It is unfair to absent class members
if there is a significant likelihood their recovery will be
diluted by fraudulent or inaccurate claims. In this case, as we
discuss, there is the possibility that Carrera‟s proposed
method for ascertaining the class via affidavits will dilute the
recovery of true class members.

        Bayer too has an interest in ensuring it pays only
legitimate claims. If fraudulent or inaccurate claims
materially reduce true class members‟ relief, these class
members could argue the named plaintiff did not adequately
represent them because he proceeded with the understanding
that absent members may get less than full relief.7 When class
members are not adequately represented by the named
plaintiff, they are not bound by the judgment. See Hansberry
v. Lee, 311 U.S. 32, 42 (1940) (explaining that due process
requires the interests of absent class members to be
adequately represented for them to be bound by the
judgment). They could then bring a new action against Bayer
and, perhaps, apply the principles of issue preclusion to

7
  We express no opinion on whether absent class members
would be successful in arguing they were not adequately
represented on this ground.




                              17
prevent Bayer from re-litigating whether it is liable under the
FDUTPA. Bayer has a substantial interest in ensuring this
does not happen. Accordingly, we reject Carrera‟s argument
that the level of proof for ascertainability should be relaxed
because Bayer‟s ultimate liability will not be based on the
affidavits.

                               3.

       Finally, Carrera argues that a screening method such as
the one described in the Prutsman Declaration will ensure that
Bayer pays claims based only on reliable affidavits. In his
declaration, James Prutsman states that he works at Rust
Consulting, Inc., a firm that has administered class
settlements for nearly 25 years. A992. He explains that Rust
“employs numerous methods to detect claims that are
submitted fraudulently.” A995. “For example, the firm runs
programmatic audits to identify duplicate claims, outliers, and
other situations. In addition, Rust has successfully utilized
fraud prevention techniques where by [sic] the claim form
offers claim options that do not reflect valid product
descriptions, prices paid, geographic locations or
combinations of such factors.” Id. “By providing claims
options such as a very high pill count or significantly higher
purchase price in this case, fraudulent claim filers would
naturally be inclined to select options that they believe would
increase their claim value. As such, techniques such as these
can be used to effectively [eliminate] fraudulent claims.” Id.

       Bayer maintains the Prutsman Declaration is
insufficient to satisfy the reliability standard because it only
addresses methods for allocating payment to a settlement
class. This fact is important, according to Bayer, because




                              18
there are different standards for approving a settlement class
than for certifying a litigation class, and because Prutsman
does not opine that his method would satisfy the standard for
class certification. Bayer also argues that just because some
defendants have agreed to use such techniques in
administering a class settlement, it does not mean that it is
sufficiently reliable.

        The Prutsman Declaration does not show the affidavits
will be reliable.8 Nor does it propose a model for screening
claims that is specific to this case. And even if Prutsman
produced a model that is specific to this case, we doubt
whether it could satisfy the ascertainability requirement. At
this stage in the litigation, the district court will not actually
see the model in action. Rather, it will just be told how the
model will operate with the plaintiff‟s assurances it will be
effective. Such assurances that a party “intends or plans to
meet the requirements” are insufficient to satisfy Rule 23.
Hydrogen Peroxide, 552 F.3d at 318; see also Comcast Corp.
v. Behrend, 133 S. Ct. 1426, 1434 (2013) (rejecting
contention that Rule 23 is satisfied by an assurance that the
plaintiffs can produce a damages model capable of measuring
damages caused by a specific theory of antitrust impact).
Carrera has suggested no way to determine the reliability of
such a model. For example, even if a model screens out a

8
  Based on this conclusion, we do not need to reach Bayer‟s
argument that the District Court erred by considering the
Prutsman Declaration, which was produced with Carrera‟s
reply brief in support of its motion for class certification.
Accordingly, we will deny Bayer‟s motion to supplement the
appellate record, which relates solely to this issue.




                               19
significant number of claims, say 25%, there is probably no
way to know if the true number of fraudulent or inaccurate
claims was actually 5% or 50%.9

        As Marcus was decided after the trial court certified
the class, Carrera should have another opportunity to satisfy
the ascertainability requirement. Accordingly, we will afford
Carrera the opportunity to submit a screening model specific
to this case and prove how the model will be reliable and how
it would allow Bayer to challenge the affidavits. Mere
assurances that a model can screen out unreliable affidavits
will be insufficient.10
                             VI.

       For the foregoing reasons, we will vacate the District
Court‟s order certifying the class action and remand for
further proceedings consistent with this opinion. Because
Marcus was decided after the court‟s certification of the class,
Carrera should be allowed to conduct further, limited

9
  Carrera‟s ability to meet the ascertainability requirement
using a screening model is further in doubt due to his inability
to clearly remember his purchases of WeightSmart, although
the District Court did not determine whether his testimony
was reliable. It would appear that the less reliable a class
member‟s memory is, the more reliable any screening method
would have to be.
10
   Bayer also argues that because the statute of limitations
will bar some claims, the class cannot be ascertained. Because
the class is defined as all purchasers of WeightSmart in
Florida, whether an individual‟s claim is barred by the statute
of limitations is not an aspect of ascertainability in this case.




                               20
discovery on the issue of ascertainability and afforded another
opportunity to satisfy the ascertainability requirement.




                              21
