UNITED STATES DISTRICT COURT

NORTHERN DISTRICT OF ILLINOIS

EASTERN DIVISION

MARK HANSEN, and JASON BUFFER,

Plaintiffs,

v.

UNITED AIRLINES, INC.,

Defendant.

Case No. 1:20-cv-02142

Hon. Thomas M. Durkin

Magistrate Judge Jeffrey T. Gilbert

UNITED AIRLINES, INC.’S REPLY IN SUPPORT OF ITS 

MOTION TO EXCLUDE THE EXPERT OPINIONS OF SEAN T. MALONE

REDACTED VERSION FILED PUBLICLY

UNREDACTED VERSION FILED UNDER SEAL PER AGREED CONFIDENTIALITY 

ORDER (DKT. 96)

Patricia Brown Holmes

Sondra A. Hemeryck

Eli J. Litoff

Brendan J. Gerdes

RILEY SAFER HOLMES & CANCILA LLP

70 W. Madison Street, Suite 2900

Chicago, IL 60602

Tel. 312-471-8700

Fax 312-471-8701

pholmes@rshc-law.com

shemeryck@rshc-law.com

elitoff@rshc-law.com

bgerdes@rshc-law.com

Attorneys for Defendant United Airlines, Inc.

Case: 1:20-cv-02142 Document #: 205 Filed: 12/01/23 Page 1 of 18 PageID #:5052
i

TABLE OF CONTENTS

Page

INTRODUCTION .......................................................................................................................... 1

ARGUMENT.................................................................................................................................. 1

I. Plaintiffs’ Argument That Dr. Malone’s Unreliable Opinions Should Be Allowed 

Because of Supposed Deficiencies in United’s Data is Meritless. ..................................... 1

II. Dr. Malone’s Proposed Methodology for Identifying and Estimating the Number of 

Class Members Is Demonstrably Unreliable. ..................................................................... 3

A. Dr. Malone’s Proposed Methodology to Identify Itineraries Cancelled by 

United is Unreliable. ............................................................................................... 3

B. Dr. Malone’s Methodology to Exclude Itineraries Impacted by Travel 

Restrictions is Based Upon Pure Speculation......................................................... 6

III. Dr. Malone’s Additional Opinion That Other Data Could Theoretically Identify the 

Majority of Refund-Eligible Customers Should Be Excluded. .......................................... 8

CONCLUSION............................................................................................................................. 13

Case: 1:20-cv-02142 Document #: 205 Filed: 12/01/23 Page 2 of 18 PageID #:5053
ii

TABLE OF AUTHORITIES

Page

CASES

Bielskis v. Louisville Ladder, Inc.,

663 F.3d 887 (7th Cir. 2011) .....................................................................................................2

Burns v. Sherwin-Williams Co.,

No. 19-CV-5258, 2022 WL 4329417 (N.D. Ill. Sept. 18, 2022), aff’d, No. 22-2825, 2023 WL 

5210857 (7th Cir. Aug. 15, 2023)............................................................................................10

Chapman v. Maytag Corp.,

297 F.2d 682 (7th Cir. 2002) ...................................................................................................11

Daubert v. Merrell Dow Pharmaceuticals, Inc.,

509 U.S. 579 (1993)......................................................................................................... passim

In re Dealer Management Systems Antitrust Litigation,

581 F. Supp. 3d 1029 (N.D. Ill. 2022)...................................................................................2, 3

Dhillon v. Crown Controls Corp.,

269 F.3d 865 (7th Cir. 2001) ...................................................................................................11

Gravitt v. Mentor Worldwide LLC,

342 F.R.D. 130 (N.D. Ill. 2022).............................................................................................8, 9

Kirk v. Clark Equip. Co.,

991 F.3d 865 (7th Cir. 2021) .....................................................................................................7

Lang v. Progressive Exp. Ins. Co.,

No. 11-C-0188, 2012 WL 1409936 (E.D. Wis. Apr. 20, 2012) ..............................................11

Manpower, Inc. v. Insurance Company of Pennsylvania,

732 F.3d 796 (7th Cir. 2013) .....................................................................................................2

Mister v. Illinois Cent. Gulf R. Co.,

639 F. Supp. 1560 (S.D. Ill. 1986).............................................................................................2

Mister v. Illinois Central Gulf Railroad Co.,

832 F.2d 1427 (7th Cir. 1987) ...................................................................................................2

Q Sales & Leasing, LLC. v. Quilt Protection, Inc., 

No. 01 C 1993, 2004 WL 2420640 (N.D. Ill. Oct. 26, 2004)..................................................12

Smith v. Ford Motor Co.,

215 F.3d 713 (7th Cir. 2000) .....................................................................................................2

Case: 1:20-cv-02142 Document #: 205 Filed: 12/01/23 Page 3 of 18 PageID #:5054
iii

Smith v. Gen. Elec. Co.,

No. CIV.A.91-12912-RGS, 2004 WL 870832 (D. Mass. Apr. 23, 2004)...............................13

Southwire Co. v. J.P. Morgan Chase & Co.,

548 F. Supp. 2d 908 (W.D. Wisc. 2007)....................................................................................3

Varlen Corp. v. Liberty Mut. Ins. Co.,

924 F.3d 456 (7th Cir. 2019) ...................................................................................................10

Walden v. City of Chicago,

755 F. Supp. 2d 942 (N.D. Ill. 2010).........................................................................................3

In re Zurn Pex Plumbing Products Liability Litigation,

644 F.3d 604 (2011)...........................................................................................................12, 13

RULES

Fed. R. Civ. P. 23.............................................................................................................................9

Fed. R. of Evid. 702 ...............................................................................................................1, 9, 13

Case: 1:20-cv-02142 Document #: 205 Filed: 12/01/23 Page 4 of 18 PageID #:5055
INTRODUCTION

United demonstrated through its Motion to Exclude the Opinions of Sean T. Malone (Dkt. 

182, “Motion”) and supporting Memorandum of Law (Dkt. 183, “Memorandum”) that Dr. 

Malone’s opinions are not admissible and should be excluded because they are based on an 

unreliable methodology and, in some cases, no methodology whatsoever. Plaintiffs’ Opposition 

(Dkt. 204, “Opposition”) sidesteps and mischaracterizes United’s arguments and does not remotely 

satisfy Plaintiffs’ burden to establish the admissibility of Dr. Malone’s opinions. For the reasons 

stated below and in United’s Memorandum, Dr. Malone’s testimony should be excluded under 

Federal Rule of Evidence 702 and Daubert v. Merrell Dow Pharmaceuticals, Inc., 509 U.S. 579 

(1993). 

ARGUMENT

I. Plaintiffs’ Argument That Dr. Malone’s Unreliable Opinions Should Be Allowed 

Because of Supposed Deficiencies in United’s Data is Meritless.

United’s Memorandum described several ways in which Dr. Malone’s methodology for 

identifying and estimating the number of class members is unreliable. Mem. at 5-10. Plaintiffs’ 

principal response, which permeates their Opposition, is to argue that United cannot rely on “selfimposed deficiencies in United’s data” to exclude Dr. Malone’s opinions. See, e.g., Opp. at 4-5. 

This argument is a complete red herring, because United’s arguments do not rely on supposed data 

deficiencies. There is nothing wrong with United’s data and United has not once suggested that 

the data Dr. Malone analyzed is inaccurate or defective. The problem lies in the way in which Dr. 

Malone seeks to utilize the data and the reliability of the conclusions he claims can be drawn from 

it. The data is fine, but Dr. Malone’s methodology (or lack thereof) for identifying putative class 

members is flawed.

Case: 1:20-cv-02142 Document #: 205 Filed: 12/01/23 Page 5 of 18 PageID #:5056
2

For these and other reasons, none of the Seventh Circuit cases cited by Plaintiffs in support 

of their “bad data” straw-man undercut United’s arguments. In fact, each supports United’s 

position that this Court should carefully scrutinize Dr. Malone’s methodology and exclude his 

opinions because the methodology is unsound. 

For example, in Manpower, Inc. v. Insurance Company of Pennsylvania, 732 F.3d 796 (7th 

Cir. 2013), the court simply acknowledged the unremarkable principle that reliability “is primarily 

a question of the validity of the methodology employed by an expert, not the quality of the data 

used in applying the methodology or the conclusions produced.” Id. at 806 (emphasis added). In

Smith v. Ford Motor Co., 215 F.3d 713 (7th Cir. 2000), while the court held that the jury should 

ordinarily resolve disputes about “the factual underpinnings of the expert’s analysis,” it also 

“emphasized that the court’s gatekeeping function focuses on an examination of the expert’s 

methodology.” Id. at 718.1In Mister v. Illinois Central Gulf Railroad Co., 832 F.2d 1427 (7th Cir. 

1987), the court affirmed a district court’s findings of fact and conclusions of law, following a 

bench trial, that the data at issue was “good enough” to support the expert’s conclusions. Id. at 

1430. The opinion affirmed by the Seventh Circuit in Mister makes clear that even if data is 

inaccurate (which is not the case here), the pertinent inquiry “is whether these flaws affected [the 

expert’s] analysis.” Mister v. Illinois Cent. Gulf R. Co., 639 F. Supp. 1560, 1574 (S.D. Ill. 1986).

The Mister case thus confirms that the focus is on the expert’s methodology, which is exactly what 

United addressed in its Motion and Memorandum. 

Plaintiffs’ other authority is inapposite. In re Dealer Management Systems Antitrust 

Litigation, 581 F. Supp. 3d 1029 (N.D. Ill. 2022), addressed a circumstance where the parties’ 

1 Notably, the Seventh Circuit has rejected attempts to stretch Smith too far, noting that Smith explicitly 

stated courts are permitted to scrutinize whether “it was appropriate for the expert to rely on ... the sources 

of information which he employed.” Bielskis v. Louisville Ladder, Inc., 663 F.3d 887, 896 (7th Cir. 2011) 

(quoting Smith and excluding expert opinion).

Case: 1:20-cv-02142 Document #: 205 Filed: 12/01/23 Page 6 of 18 PageID #:5057
3

experts expressed competing views, but both of them had a “factual basis” for their opinions and 

a “rational connection between the data and the opinion.” Id. at 1032. That is not the case here, as 

Dr. Malone’s opinions are completely untethered to the data, consist of pure speculation, and in 

some cases, are flatly contradicted by the undisputed facts. See generally Mem. at 5-14. Plaintiffs 

also cite Walden v. City of Chicago, 755 F. Supp. 2d 942, 953 (N.D. Ill. 2010), for the proposition

that “100% accuracy” of data reviewed by an expert is not required. Of course that is true. But the 

point of Walden is that the expert there employed a reliable methodology in searching and

analyzing the data. Id. Specifically, the court found the methodology was designed “to mitigate the 

inaccuracies” in the data and was consistent with the methods applied by other experts in the field. 

Id. Finally, Southwire Co. v. J.P. Morgan Chase & Co., 548 F. Supp. 2d 908 (W.D. Wisc. 2007), 

has no bearing on this case whatsoever because there, “Defendants d[id] not challenge the methods 

employed by plaintiffs’ experts.” Id. at 935.

Accordingly, the Court should disregard Plaintiffs’ arguments about purported data 

deficiencies. As explained in more detail below, Plaintiffs have failed to rebut any of the arguments 

that United actually made in support of its Motion, which are not based deficiencies in the data, 

but rather on Dr. Malone employing a methodology that is contradicted by the undisputed facts or, 

in other instances, employing no methodology at all. 

II. Dr. Malone’s Proposed Methodology for Identifying and Estimating the Number of 

Class Members Is Demonstrably Unreliable.

A. Dr. Malone’s Proposed Methodology to Identify Itineraries Cancelled by 

United is Unreliable.

As set forth in United’s Memorandum, Dr. Malone’s use of the 

 to exclude passengers who voluntarily cancelled their itineraries is not a reliable methodology 

because the undisputed facts demonstrate that 

Mem. at 5-8. Indeed, as United showed and Plaintiffs do not dispute, Dr. Malone’s 

Case: 1:20-cv-02142 Document #: 205 Filed: 12/01/23 Page 7 of 18 PageID #:5058
4

flawed methodology would exclude Plaintiff Buffer from the class even though the parties agree

that he did not voluntarily cancel his itinerary. Id. at 7-8.

In response, Plaintiffs attempt to pivot: they contend that Dr. Malone used 

 to identify passengers who changed their itineraries rather than 

those who cancelled them. That is not, however, what Dr. Malone said. In Paragraph 20 of his 

report, Dr. Malone states:

Mem., Ex. 2 ¶ 20 (emphasis added). In other words, the only “changes” to travel in which Dr. 

Malone was interested, and for which he used , were 

cancellations. Dr. Malone confirmed in his deposition that this was the case. See Malone Dep.

(Dkt. 182-5) at 63:24-64:6 (explaining that “the purpose of [analyzing this data field] was to focus 

on identifying ticketed passengers whose itineraries were ultimately canceled by United.”) 

(emphasis added); id. at 111:23-112:4 (“I was focusing on ticketed passengers whose itineraries 

were ultimately canceled by United, who didn’t make changes themselves.”) (emphasis added).

And perhaps most telling, Plaintiffs expressly relied on Dr. Malone’s use of 

 to “exclude persons who initiated the changes to their travel (i.e., 

cancelled their itinerary)” in arguing that this Court should certify their proposed Classes. 

Plaintiffs’ Mem. in Support of Mot. for Class Cert. (Dkt. 172, “Plfs. Class Cert. Br.”) at 12-13 

(citing Malone Report ¶¶ 17-18, 20) (emphasis added). Plaintiffs cannot avoid the fatal flaws in 

Dr. Malone’s methodology by misstating what he did.

Case: 1:20-cv-02142 Document #: 205 Filed: 12/01/23 Page 8 of 18 PageID #:5059
5

In any event, Plaintiffs’ attempted pivot does nothing to salvage Dr. Malone’s opinions. If 

Dr. Malone really made no effort to limit his identification of class members to itineraries 

cancelled by United, then his methodology is unsound, and his opinions are irrelevant, for that

reason as well. Only customers whose itineraries were cancelled by United could possibly be 

members of the putative class (see Plfs. Class Cert. Br. at 1-2, proposed class definitions), so a 

methodology that does not exclude voluntarily cancellations could not possibly reliably identify 

or estimate the number of class members. 

Next, Plaintiffs make a bizarre argument: they assert that because United’s expert, Michael 

Petron, employed an appropriate methodology to exclude passengers who voluntarily cancelled 

their itineraries, “refund-eligible passengers can[] be identified using United’s records.” Opp. at 6. 

But the pertinent question for this Motion is not whether another expert using a reliable

methodology can exclude voluntary cancellations from the purported class; the question is whether 

Dr. Malone can do so using his methodology. And the answer is a resounding no.

Plaintiffs’ attempt to adopt Mr. Petron’s methodology also fails because Plaintiffs 

fundamentally misunderstand or mischaracterize Mr. Petron’s opinions. They contend that while 

he and Dr. Malone “may differ in the magnitude of their opinions on class size, each confirms that 

class members can be identified from United’s records.” Opp. at 7. What Mr. Petron actually 

concluded, however, is 

. See Petron Rebuttal Report, 

Dkt. 183, Ex. 5, ¶¶ 29-90. Nothing about Mr. Petron’s opinions supports Dr. Malone’s flawed 

methodology. 

Plaintiffs also make a futile attempt address the fact that Dr. Malone’s methodology would 

exclude Buffer from the putative class. Plaintiffs concede that Dr. Malone’s methodology does not 

Case: 1:20-cv-02142 Document #: 205 Filed: 12/01/23 Page 9 of 18 PageID #:5060
6

work when it comes to Buffer. But as they do throughout the Opposition, they attempt to blame 

this failure on supposed deficiencies in United’s data, stating: “United’s own expert highlighted 

United’s data deficiencies, writing that Plaintiff Buffer’s 

 Opp. at 4 (quoting Petron Report ¶ 42.m). Again, Plaintiffs 

fundamentally mischaracterize Mr. Petron’s opinions and United’s data. There is no problem with 

United’s data. In fact, it is possible to determine from United’s documents whether Plaintiff Buffer 

voluntarily cancelled his itinerary. It is undisputed that Plaintiff Buffer did not voluntarily cancel: 

SWISS International cancelled Buffer’s flights on March 12, 2020, and United informed Buffer of 

the cancellation on March 14, 2020. See Reply in Support of Mot. for Summary Judgment, Dkt. 

197 at 3-4.

The problem for Dr. Malone (and for Plaintiffs’ class certification arguments) is that this 

information can only be determined by conducting a manual review of the individualized records 

related to Buffer. See Mem. in Support of Mot. for Summary Judgment, Dkt. 175 at 16-18. And 

that is precisely what Mr. Petron concluded: 

. Petron Rebuttal Report, 

Dkt. 183, Ex. 5, ¶¶ 29-62.

In short, Plaintiffs have failed to establish the reliability of Dr. Malone’s methodology for 

excluding passengers who voluntarily cancelled their own itineraries. Dr. Malone’s proposed 

methodology is contrary to the undisputed facts, and, therefore, his opinion as to the identification 

and estimated number of class members should be excluded. 

B. Dr. Malone’s Methodology to Exclude Itineraries Impacted by Travel 

Restrictions is Based Upon Pure Speculation.

Next, United’s Motion explained that Dr. Malone’s proposed methodology to exclude 

itineraries impacted by travel restrictions was based on nothing more than his own untested 

Case: 1:20-cv-02142 Document #: 205 Filed: 12/01/23 Page 10 of 18 PageID #:5061
7

speculation. Mem. at 8-10. Dr. Malone opined that 

. Id. In fact, he did not attempt to 

test his opinion at all, and instead simply speculated that unidentified and unreviewed documents 

could somehow be used to systematically exclude these passengers. Id. 

Plaintiffs’ Opposition does not meaningfully engage with these arguments. Plaintiffs assert 

only that are just another data point,” “the filtering process for United’s data is 

easy,” and that Dr. Malone’s ability to filter data should be “far from controversial” because it is 

“basic data analysis.” Opp. at 8-9. The problem with Dr. Malone’s methodology is not with his 

ability to filter the data . As United explained in its Memorandum, 

Mem. at 8-9. But Dr. Malone made no 

attempt to obtain or review any information on travel restrictions or otherwise test his assertion 

that . Id. In fact, Dr. 

Malone was not even aware of any documentation produced in this case regarding travel 

restrictions, nor did he request any from Plaintiffs’ counsel. Id. Instead, he speculated that 

, although he never endeavored to do so. Id. at 

9. Nor did he ever attempt to test his theory that he could 

a failure that 

weighs heavily in the Daubert analysis. Id. at 10; see also Kirk v. Clark Equip. Co., 991 F.3d 865, 

877 (7th Cir. 2021) (holding an expert’s failure to test his hypothesis supported exclusion where 

the testing “may very well have provided [the expert] with additional, valuable information in 

forming his causation opinion”). 

Case: 1:20-cv-02142 Document #: 205 Filed: 12/01/23 Page 11 of 18 PageID #:5062
8

The Opposition does not even attempt to address these fatal flaws in Dr. Malone’s 

methodology and his opinions should, therefore, be excluded.

III. Dr. Malone’s Additional Opinion That Other Data Could Theoretically Identify the 

Majority of Refund-Eligible Customers Should Be Excluded.

As set forth in United’s Memorandum, Dr. Malone’s belated opinion that he could 

also should be excluded because (1) it is an improper rebuttal opinion, and (2) it is based on pure 

speculation. Mem. at 11-14.

In response to the first argument, Plaintiffs assert that Dr. Malone’s new opinion merely 

flowed from his criticism of Mr. Petron’s report, which argued that 

Opp. at 10. This argument misses the mark and attempts to shift the burden of proof on 

Plaintiffs’ claims. 

“A plaintiff who knows that the defendant means to contest an issue that is germane to the 

prima facie case (as distinct from an affirmative defense) must put in his evidence on the issue as 

part of his case in chief.” Gravitt v. Mentor Worldwide LLC, 342 F.R.D. 130, 135 (N.D. Ill. 2022) 

(granting motion to strike improper expert rebuttal report). Therefore, “evidence for an argument 

that should have been made in the case in chief is improper on rebuttal. Otherwise, the plaintiff 

could reverse the order of proof, in effect requiring the defendants to put in their evidence before 

the plaintiff put in his.” Id. (cleaned up). What flows from these basic principles is that if an 

expert’s opinions “go directly to” an element on which the plaintiff bears the burden of proof, those 

opinions “belong[] in the opening expert reports.” Id. 

The circumstance described in Gravitt is exactly what has transpired here. Dr. Malone 

made no attempt to identify refund-eligible passengers in his opening report, even though 

Case: 1:20-cv-02142 Document #: 205 Filed: 12/01/23 Page 12 of 18 PageID #:5063
9

identification of refund-eligible passengers is a key and contested issue on which Plaintiffs have 

the burden. Mem. at 11-12. Then, after Mr. Petron predictably addressed those issues in his report, 

Dr. Malone proffered an entirely new opinion in rebuttal, speculating that 

, thereby 

depriving Mr. Petron the opportunity to rebut those opinions. 

“[T]hose matters [on which Dr. Malone opined in his rebuttal report] go directly to” 

establishing elements on which Plaintiffs’ bear the burden of proof. Gravitt, 342 F.R.D. at 135.

Specifically, Plaintiffs must prove refund-eligibility to establish the breach element of their breach 

of contract claims, because if class members are not entitled to a refund under United’s Contract 

of Carriage, then United’s alleged failure to provide refunds was not a breach. Additionally, 

Plaintiffs bear the burden to establish that the putative class should be certified pursuant to Federal 

Rule of Civil Procedure 23, and Dr. Malone’s (in)ability to systematically identify refund-eligible 

passengers goes directly to commonality, predominance, and other factors on which Plaintiffs bear 

the burden. Accordingly, Dr. Malone’s opinions regarding refund-eligibility were required to be

disclosed in his opening report. That Dr. Malone’s rebuttal “report makes a few references to 

[United’s] expert[] does not make it proper rebuttal.” Gravitt, 342 F.R.D. at 135. Accordingly, the 

opinion should be stricken as improper rebuttal.

In any event, as United explained in its Memorandum, Dr. Malone’s opinion should also 

be excluded under Daubert and Rule 702 because it relies on nothing more than his own 

speculation and say-so. Plaintiffs insist that the Court should not exclude Dr. Malone’s opinions 

on this basis because doing so would impermissibly usurp the jury’s role to examine the 

“underlying facts” of his opinion. Opp. at 11-12. But United’s primary argument here is that there 

are no underlying facts or tests being relied upon. See Mem. at 13. Indeed, Plaintiffs and Dr. 

Case: 1:20-cv-02142 Document #: 205 Filed: 12/01/23 Page 13 of 18 PageID #:5064
10

Malone cannot even state—as is their burden—that these “unproduced relevant data” sets even 

exist, much less what they would show. Thus, Dr. Malone’s opinion is nothing more than 

speculation layered on top of speculation. 

For instance, although Dr. Malone opined that he 

offers no information on how that data is stored, what the forms supposedly contain, how many 

passengers used the forms, or, crucially, how the data (if it exists) could be used to identify

customers who requested refunds. Id. Similarly, his opinion that 

 is not based on any testing or tangible underlying 

facts. Id. Indeed, Dr. Malone has no information concerning the number or percentage of customers 

who request refunds via email, has not reviewed any United emails, has not run any searches for 

keywords in an effort to locate emails related to refund requests, and has no information about the 

number of hits his theoretical searches would return. Mem. at 14. Where, as here, the “underlying 

facts” being relied upon are just speculation and say-so, it absolutely within the Court’s 

gatekeeping function to exclude the opinion. See Daubert, 509 U.S. at 590 (opinion cannot be 

based on “unsupported speculation”); see also See Varlen Corp. v. Liberty Mut. Ins. Co., 924 F.3d 

456, 460 (7th Cir. 2019) (expert properly excluded where he failed “to articulate a justification for 

his inference ... beyond a simple say-so.”); Burns v. Sherwin-Williams Co., No. 19-CV-5258, 2022 

WL 4329417, at *25 (N.D. Ill. Sept. 18, 2022), aff’d, No. 22-2825, 2023 WL 5210857 (7th Cir. 

Aug. 15, 2023) (“An expert’s opinion must rest on something, above and beyond the expert’s sayso.”).

2

2 Plaintiffs appear to suggest in passing that United was required to submit a “declaration or affidavit 

confirming that the data [which Dr. Malone speculates would support his opinion] does not exist.” Opp. at 

11. The Court should disregard this suggestion for two reasons. First, it again attempts to turn the burden 

of proof on its head. Plaintiffs bear the burden to establish the admissibility of their expert’s opinions. If 

Case: 1:20-cv-02142 Document #: 205 Filed: 12/01/23 Page 14 of 18 PageID #:5065
11

Plaintiffs attempt to downplay Dr. Malone’s failure to test any of his speculation about 

what unreviewed documents might show, contending that the “absence [of testing] alone is not 

fatal to an expert’s testimony.” Opp. at 12. But testing (and an expert’s failure to conduct any tests) 

is an important factor in the Daubert analysis. Mem. at 10. Indeed, the cases Plaintiffs cite to show 

that it is an important factor. See Dhillon v. Crown Controls Corp., 269 F.3d 865, 867 (7th Cir. 

2001) (“When, as in this case, an expert has not engaged in any type of testing ... it is not an abuse 

of discretion for the district court to refuse to allow such testimony.”); Lang v. Progressive Exp. 

Ins. Co., No. 11-C-0188, 2012 WL 1409936, at *4 (E.D. Wis. Apr. 20, 2012) (“The Seventh Circuit 

has recognized that a failure to test may render an opinion unreliable and inadmissible ...”) (citing 

Chapman v. Maytag Corp., 297 F.2d 682, 688 (7th Cir. 2002). 

This is precisely the type of case where a failure to test is so important. As discussed herein 

and in United’s Memorandum, Dr. Malone did (to an extent) test his opinions that 

. That he conducted that analysis and explained his hypotheses and conclusions 

has provided United with the opportunity to challenge his methodology. But by failing to conduct 

any analysis with respect to 

, he has prevented United from “testing [his hypotheses] to see if 

they can be falsified.” Daubert, 509 U.S. at 593. That is precisely what Daubert and our adversarial 

plaintiffs believed that additional, unproduced data in United’s possession was required to support their 

class certification arguments, they should have propounded an appropriate request for production and 

brought an appropriate motion for the Court’s consideration prior to the close of discovery. Second, whether 

or not the data exists is not at issue. The issue is Dr. Malone’s speculative opinion that 

. See Mot. at 11. Because he has never reviewed the data (whether it exists or not), 

his opinion is based on pure speculation.

Case: 1:20-cv-02142 Document #: 205 Filed: 12/01/23 Page 15 of 18 PageID #:5066
12

system in general contemplate. Dr. Malone cannot be allowed to base his opinions on “unsupported 

speculation.” Id. at 590. 

Finally, Plaintiffs futilely attempt to address the fact that Dr. Malone’s speculative theory 

is inconsistent with Plaintiffs’ allegations, because none of the data sources he speculates could be 

searched for refund requests reflect any request made by Buffer or Hansen. See Mem. at 14; Opp. 

at 12-13. Once again, Plaintiffs blame this undisputed fact (see Reply in Support of Mot. for 

Summary Judgment, Dkt. 197 at 3) on purported deficiencies in United’s recordkeeping. Opp. at 

12-13. But Plaintiffs’ own allegations confirm this is not a problem with United’s data: neither 

Plaintiff alleges they made a refund request via email or a web 

 There is no data issue here—the data shows exactly 

what Plaintiffs allege it would show.

Moreover, the cases Plaintiffs cite are irrelevant because in each of the cited cases, the 

expert actually conducted testing and employed a methodology, but was somewhat limited by the 

data at issue. Here, Malone has no methodology, has not even reviewed the data at issue, and the 

Plaintiffs own allegations confirm that the data, if searched by Dr. Malone, would not reflect refund 

requests from either of them. Thus, Plaintiffs’ cited authority actually supports United. For 

example, Q Sales & Leasing, LLC. v. Quilt Protection, Inc. was a lost-profit case where the expert 

conducted extensive analysis of the defendant’s financial statements, and determined it was 

impossible to distinguish between infringing and non-infringing revenues. No. 01 C 1993, 2004 

WL 2420640, at *2 (N.D. Ill. Oct. 26, 2004). Notably, the court reserved ruling on whether to 

exclude the expert testimony until the Plaintiff explained its efforts to obtain the data it supposedly 

needed. Id. The Eighth Circuit’s decision in In re Zurn Pex Plumbing Products Liability Litigation

is wholly inapplicable because there, “[b]oth sides agree[d]” that the experts “used generally 

Case: 1:20-cv-02142 Document #: 205 Filed: 12/01/23 Page 16 of 18 PageID #:5067
13

recognized and reliable methodologies,” and simply disagreed over the scope of the Daubert 

analysis to be conducted at the class certification stage. 644 F.3d 604, 611 (2011). Notably, the 

court distinguished applicable Seventh Circuit authority on the subject, and ultimately concluded

that the expert’s methodology was reliable for purposes of supporting class certification. Id. at 611-

12. Lastly, Plaintiffs cite dicta from a footnote in an out-of-circuit trial court opinion. See Smith v. 

Gen. Elec. Co., No. CIV.A.91-12912-RGS, 2004 WL 870832, at *1 n.2 (D. Mass. Apr. 23, 2004). 

But again, in that case, the expert had actually performed calculations from the data produced, not 

speculated about what unproduced data might show, and in any event, the defendants had 

“accepted” the expert’s calculations. Id. 

In sum, Dr. Malone’s opinion regarding the identification of refund-eligible passengers 

should be stricken as improper rebuttal. And in any event, the opinion should be excluded because 

it is not based upon any methodology; it is instead based solely upon speculation about what 

unproduced data might show. 

CONCLUSION

For the foregoing reasons and the additional reasons set forth in United’s Memorandum, 

Dr. Malone’s proposed opinions are inadmissible under Rule 702 and Daubert and should be 

excluded.

Dated: December 1, 2023 /s/ Sondra A. Hemeryck

Patricia Brown Holmes

Sondra A. Hemeryck

Eli J. Litoff

Brendan J. Gerdes

RILEY SAFER HOLMES & CANCILA LLP

70 W. Madison Street, Suite 2900

Chicago, IL 60602

Tel. 312-471-8700

Fax 312-471-8701

Case: 1:20-cv-02142 Document #: 205 Filed: 12/01/23 Page 17 of 18 PageID #:5068
14

pholmes@rshc-law.com

shemeryck@rshc-law.com

elitoff@rshc-law.com

bgerdes@rshc-law.com

Attorneys for Defendant United Airlines, Inc.

Case: 1:20-cv-02142 Document #: 205 Filed: 12/01/23 Page 18 of 18 PageID #:5069