FOR PUBLICATION

UNITED STATES COURT OF APPEALS

FOR THE NINTH CIRCUIT

EDWIN HARDEMAN,

Plaintiff-Appellee/

Cross-Appellant,

v.

MONSANTO COMPANY,

Defendant-Appellant/

Cross-Appellee.

Nos. 19-16636

19-16708

D.C. Nos.

3:16-cv-00525-VC

3:16-md-02741-VC

OPINION

Appeal from the United States District Court

for the Northern District of California

Vince G. Chhabria, District Judge, Presiding

Argued and Submitted October 23, 2020

San Francisco, California

Filed May 14, 2021

Before: Michael D. Hawkins, N. Randy Smith, and

Ryan D. Nelson, Circuit Judges.

Opinion by Judge R. Nelson;

Dissent by Judge N.R. Smith
2 HARDEMAN V. MONSANTO

SUMMARY*

Pesticides / Punitive Damages

The panel affirmed the district court’s judgment in favor 

of Edwin Hardeman in his action alleging that Monsanto’s 

pesticide, Roundup, caused his non-Hodgkin’s lymphoma.

Roundup is pesticide with the active ingredient 

glyphosate. Since 2015, thousands of cancer victims sued 

Monsanto in state and federal court. This appeal arose out 

of the first bellwether trial for the federal cases consolidated 

in a multidistrict litigation. The jury awarded Hardeman 

$5,267.634.10 in compensatory damages, and $75 million in 

punitive damages. The district court reduced the punitive 

damages award to $20 million.

The panel held that Hardeman’s state failure-to-warn 

claims based on Roundup’s labeling were consistent with the 

Federal Insecticide, Fungicide, and Rodenticide Act 

(“FIFRA”) and thus were neither expressly nor impliedly 

preempted. Specifically, the panel affirmed the district 

court’s conclusion that Hardeman’s state failure-to-warn 

claims were “equivalent to” and “fully consistent with” 

FIFRA and therefore not expressly preempted. Bates v. Dow 

Agrosciences LLC, 554 U.S. 431, 449 (2005). In addition, 

because Monsanto could comply with both FIFRA and 

California law, FIFRA did not impliedly preempt 

Hardeman’s state failure-to-warn claims.

* This summary constitutes no part of the opinion of the court. It 

has been prepared by court staff for the convenience of the reader.
HARDEMAN V. MONSANTO 3

The panel held that the district court ultimately applied 

the correct standard from Daubert v. Merrell Dow 

Pharmaceuticals, Inc., 509 U.S. 579 (1993), and did not 

abuse its discretion in admitting Hardeman’s expert 

testimony. Despite its incorrect assumption that this court 

was more permissive than others in admitting Daubert

testimony, the district court still employed the correct legal 

standard for reliability when it admitted Hardeman’s expert 

testimony. The panel held further that the district court did 

not abuse its discretion in concluding that Hardeman’s 

experts reliably based their general causation opinions on 

epidemiological evidence showing a connection between 

glyphosate and cancer. The panel also held that the district 

court did not abuse its discretion in admitting Hardeman’s 

expert testimony on specific causation to show that 

Hardeman’s cancer was caused by glyphosate, rather than 

some other factor. Here, Hardeman’s experts reliably used 

differential diagnosis because they ruled in glyphosate based 

on the epidemiological evidence supporting the general 

causation opinions and ruled out alternate causes, such as 

idiopathy and Hepatitis C (HCV).

The panel held that the district court did not abuse its 

discretion in admitting the International Agency for 

Research on Cancer’s classification of glyphosate as 

probably carcinogenic and three regulatory rejections of that 

classification by excluding evidence from other regulatory 

bodies. The panel held further that even if these evidentiary 

decisions were erroneous, any error was harmless because it 

was more probable than not that the admission of the 

evidence did not affect the jury’s verdict.

The panel held that the district court’s jury instruction on 

causation was erroneous because it was inconsistent with the 
4 HARDEMAN V. MONSANTO

Judicial Council of California Civil Jury Instructions and 

California case law, but it was harmless error.

The panel held that the district court properly denied 

Monsanto judgment as a matter of law because evidence 

showed the carcinogenic risk of glyphosate was knowable at 

the time of Hardeman’s exposure.

The panel held that evidence supported a punitive 

damages award, punitive damages were properly reduced, 

and the reduced award – while close to the outer limit – was 

constitutional. Specifically, the panel held that punitive 

damages were permissible under California law because 

substantial evidence was presented that Monsanto acted with 

malice by, among other things, ignoring Roundup’s 

carcinogenic risks. The panel held that the jury’s $75 million 

punitive damages award was “grossly excessive” given the 

mitigating factors found by the district court. However, 

considering the evidence of Monsanto’s reprehensibility, the 

district court’s reduced $20 million punitive damages award 

(a 3.8 to 1 damages ratio), while at the outer limits of 

constitutional propriety, ultimately comported with due 

process.

The panel cautioned that although this appeal involved a 

bellwether trial, many of its holdings were fact-specific, and 

different Roundup cases may present different 

considerations, leading to different results.

Judge N.R. Smith dissented to section VII.B, concerning 

punitive damages. He would hold that Monsanto’s low 

degree of reprehensibility cannot constitutionally justify the 

district court’s substantial punitive damages award. The 

facts found by the district court did not support a 3.8:1 ratio 

to compensatory damages.
HARDEMAN V. MONSANTO 5

COUNSEL

Seth P. Waxman (argued) and Paul R.Q. Wolfson, Wilmer 

Cutler Pickering Hale and Dorr LLP, Washington, D.C.; 

Thomas G. Sprankling and Henry J. Becker, Wilmer Cutler 

Pickering Hale and Dorr LLP, Palo Alto, California; Leon T. 

Kenworthy, Clair H. Chung, James Barton, Samuel M. 

Strongin, and Rafael J. Gallardo Hevia, Wilmer Cutler 

Pickering Hale and Dorr LLP, Washington, D.C.; Brian L. 

Stekloff and Rakesh Kilaru, Wilkinson Walsh and Eskovitz 

LLP, Washington, D.C.; Philip J. Perry and Richard P. 

Bress, Latham & Watkins LLP, Washington, D.C.; 

Michael X. Imbroscio and David M. Zionts, Covington & 

Burling LLP, Washington, D.C.; Lee Marshall, Bryan Cave 

Leighton Paisner LLP, San Francisco, California; for 

Defendant-Appellant/Cross-Appellee.

David J. Wool (argued) and Aimee H. Wagstaff, Andrus 

Wagstaff PC, Lakewood, Colorado; Leslie A. Brueckner, 

Public Justice, Oakland, California; Jennifer A. Moore, 

Moore Law Group PLLC, Louiseville, Kentucky; for 

Plaintiff-Appellee/Cross-Appellant.

Jonathan D. Brightbill (argued) and Eric Grant, Deputy 

Assistant Attorneys General; Jennifer Scheller Neumann, 

Varudhini Chilakamarri, and Matthew R. Oakes, Attorneys; 

Environment and Natural Resources Division, United States 

Department of Justice, Washington, D.C.; Erin S. Koch and 

Amber L. Aranda, Attorneys, EPA Office of General 

Counsel, Washington, D.C.; for Amicus Curiae United 

States.

Andrew Wiener (argued), Laura Zuckerman, and Dennis 

Ragen, Deputy Attorneys General; Harrison M. Pollack, 

Supervising Deputy Attorney General; Office of the 
6 HARDEMAN V. MONSANTO

Attorney General, Oakland, California; for Amicus Curiae 

State of California.

Shannen W. Coffin and Sara Beth Watson, Steptoe & 

Johnson LLP, Washington, D.C., for Amicus Curiae 

CropLife America.

Laura W. Brill, Nicholas F. Daum, and Sharon S. Song, 

Kendall Brill & Kelly LLP, Los Angeles, California, for 

Amicus Curiae Genentech Inc.

Douglas J. Peterson, Attorney General; Justin D. Lavene, 

Maegan L. Woita, and Joshua E. Dethlefsen, Assistant 

Attorneys General; Office of the Attorney General, Lincoln, 

Nebraska; Lawrence G. Wasden, Attorney General of Idaho; 

Jeff Landry, Attorney General of Louisiana; Wayne 

Stenehjem, Attorney General of North Dakota; Jason 

Ravnsborg, Attorney General of South Dakota; Ken Paxton, 

Attorney General of Texas; and Sean D. Reyes, Attorney 

General of Utah; for Amici Curiae States of Nebraska, 

Idaho, Louisiana, North Dakota, South Dakota, Texas, and 

Utah.

Curtis A. Cole, Cassidy C. Davenport, and Scott M. 

Klausner, Cole Pedroza LLP, San Marino, California, for 

Amici Curiae California Medical Association, California 

Dental Association, and California Hospital Association.

William R. Stein, Eric S. Parnes, Stephen R. Halpin III, and 

J. Chesley Burruss, Hughes Hubbard & Reed LLP, 

Washington, D.C.; Theodore V.H. Mayer, Hughes Hubbard 

& Reed LLP, New York, New York; Steven P. Lehotsky and 

Michael B. Schon, U.S. Chamber Litigation Center, 

Washington, D.C.; James C. Stansel and Melissa B. Kimmel, 

Pharmaceutical Research and Manufacturers of America, 
HARDEMAN V. MONSANTO 7

Washington, D.C.; for Amici Curiae Chamber of Commerce 

of the United States of America, and Pharmaceutical 

Research and Manufacturers of America.

Adina H. Rosenbaum and Allison M. Zieve, Public Citizen 

Litigation Group, Washington, D.C., for Amicus Curiae 

Public Citizen.

Matthew W.H. Wessler and Larkin Turner, Gupta Wessler 

PLLC, Washington, D.C.; Bruce Stern, President, American 

Association for Justice, Washington, D.C.; for Amicus 

Curiae American Association for Justice.

Ashley Keller, Travis Lenker, and Warren Postman, Keller 

Lenkner LLC, Chicago, Illinois; Ernest A. Young, Apex, 

North Carolina; for Amici Curiae Public Law Scholars.

Ryan D. Talbott, Center for Food Safety, Portland, Oregon, 

for Amici Curiae Center for Food Safety and Center for 

Biological Diversity.

Carrie Apfel, Earthjustice, Washington, D.C.; Alexis 

Andiman and Peter Lehner, Earthjustice, New York, New 

York; Patti Goldman, Earthjustice, Seattle, Washington; for 

Amici Curiae California Rural Legal Assistance Foundation, 

Farmworker Association of Florida, Farmworker Justice, 

Migrant Clinicians Network, Pesticide Action Network, 

United Farm Workers, and UFW Foundation.

Melanie Benesh and Caroline Leary, Environmental 

Working Group, Washington, D.C., for Amicus Curiae 

Environmental Working Group.
8 HARDEMAN V. MONSANTO

OPINION

R. NELSON, Circuit Judge:

Monsanto Company manufactures Roundup, a pesticide 

with the active ingredient glyphosate. Since 2015, thousands 

of cancer victims have sued Monsanto in state and federal 

court, alleging that Roundup caused their non-Hodgkin’s 

lymphoma. This appeal arises out of the first bellwether trial 

for the federal cases consolidated in a multidistrict litigation.

The jury returned a verdict in favor of plaintiff Edwin 

Hardeman, awarding him $5,267,634.10 in compensatory 

damages and $75 million in punitive damages. The district 

court reduced the jury’s punitive damages award to 

$20 million.

Monsanto appeals, arguing the Federal Insecticide, 

Fungicide, and Rodenticide Act (“FIFRA”) preempts 

Hardeman’s failure-to-warn claims; the district court made a 

series of evidentiary and jury instruction errors; the district 

court erred in denying judgment as a matter of law; and the 

punitive damages award violates California law and the Due 

Process Clause. Hardeman cross-appeals, arguing the jury’s 

$75 million punitive damages award was constitutional.

We affirm the district court and hold that (1) Hardeman’s 

state failure-to-warn claims are not preempted by FIFRA; 

(2) the district court ultimately applied the correct standard 

from Daubert v. Merrell Dow Pharmaceuticals, Inc.,

509 U.S. 579 (1993), and did not abuse its discretion in 

admitting Hardeman’s expert testimony; (3) the district court 

did not abuse its discretion in admitting the International 

Agency for Research on Cancer’s classification of 

glyphosate as probably carcinogenic and three regulatory 

rejections of that classification but excluding evidence from 
HARDEMAN V. MONSANTO 9

other regulatory bodies; (4) the district court’s jury 

instruction on causation, though erroneous, was harmless; 

(5) Monsanto was properly denied judgment as a matter of 

law because evidence shows the carcinogenic risk of 

glyphosate was knowable at the time of Hardeman’s 

exposure; and (6) evidence supports a punitive damages 

award, punitive damages were properly reduced, and the 

reduced award—while close to the outer limits—is 

constitutional.

I

A

Under FIFRA, the United States Environmental 

Protection Agency (“EPA”) enforces “the use, . . .sale[,] and 

labeling[] of pesticides.” Bates v. Dow Agrosciences LLC, 

544 U.S. 431, 437 (2005) (citation omitted). A state may 

“not impose or continue in effect any requirements for 

labeling or packaging in addition to or different from those” 

required by FIFRA. 7 U.S.C. § 136v(b).

FIFRA requires pesticide manufacturers to register their 

products with EPA. 7 U.S.C. § 136a(a). EPA makes 

registration determinations after considering available 

scientific data, § 136a(c)(1)(F), (c)(2)(A); 40 C.F.R. 

§ 158.500, and FIFRA requires EPA to re-review a 

pesticide’s registration, including its effects on human 

health, every fifteen years, § 136a(g)(1)(A). FIFRA states, 

however, that “[i]n no event shall registration of an article be 

construed as a defense for the commission of any offense 

under this subchapter.” § 136a(f)(2). Rather, “[a]s long as 

no cancellation proceedings are in effect,” registration of a 

pesticide is merely “prima facie evidence that the pesticide, 

its labeling and packaging comply with the registration 

provisions of the subchapter.” Id.
10 HARDEMAN V. MONSANTO

EPA can also institute cancellation proceedings, 

7 U.S.C. § 136d(b), or take other enforcement action against 

the manufacturer of a registered pesticide if the agency 

determines the product is “misbranded.” Bates, 544 U.S. 

at 439. Remedies for misbranding include civil and criminal 

penalties. Id. at 439 n.11 (citing 7 U.S.C. § 136l). A duly 

registered pesticide can be misbranded if the label “does not 

contain adequate instructions for use, or if its label omits 

necessary warnings or cautionary statements.” Bates, 

544 U.S. at 438 (citation omitted). “Because it is unlawful 

under the statute to sell a pesticide that is registered but 

nevertheless misbranded, manufacturers have a continuing 

obligation to adhere to FIFRA’s labeling requirements.” Id.

(citations omitted). This obligation includes a duty to seek 

approval to amend a label that does not contain all 

“necessary warnings or cautionary statements.” Id. (citation 

omitted).

Starting in 1974, EPA registered pesticides containing 

glyphosate, the active ingredient in Roundup.1 EPA, 

Glyphosate Proposed Interim Registration Review Decision 

4 (Apr. 2019) (“Proposed Interim Registration Review”). In 

1985, an EPA review of a mouse study found “[g]lyphosate 

was oncogenic in male mice,” causing rare tumors. EPA 

classified glyphosate as a possible human carcinogen. Since 

then, however, EPA has repeatedly approved the use of 

glyphosate as a pesticide, each time concluding that it is not 

likely to be carcinogenic to humans. See Nat’l Fam. Farm 

Coal. v. EPA, 966 F.3d 893, 905 (9th Cir. 2020).

1 Though commonly referred to as an herbicide, Roundup is defined 

as a pesticide under 7 U.S.C. § 136(t), (u). Roundup contains 

glyphosate, water, and other ingredients called “surfactants.”
HARDEMAN V. MONSANTO 11

In the early 1990s, EPA reevaluated glyphosate’s effects 

on human health as part of its regular review of glyphosate’s 

registration. After considering numerous carcinogenicity 

studies in rats and mice—including new evidence submitted 

by Monsanto—EPA changed its designation of glyphosate 

to a “Group E carcinogen” signifying “evidence of noncarcinogenicity in humans.”

In 2015, a working group at the International Agency for 

Research on Cancer (“IARC”), an agency of the World 

Health Organization, issued a report classifying glyphosate 

as a “Group 2A” agent, meaning it is “probably carcinogenic 

to humans” based on glyphosate’s “limited evidence” of 

cancer in humans and “sufficient evidence” of cancer in 

experimental animals. IARC’s classification was a “hazard 

identification,” the first step of a public health assessment 

designed to identify cancer hazards. That hazard 

determination asked whether glyphosate “is capable of 

causing cancer under some circumstances,” but did not 

include a “risk assessment” gauging the carcinogenic effects 

from real-world human exposure. Since IARC’s 

classification, other national and international agencies 

charged with reviewing pesticides—such as the European 

Union’s European Chemicals Agency (“ECA”), European 

Food Safety Authority (“EFSA”), and the national health 

authorities of Australia, Canada, Germany, and New 

Zealand—have reported that scientific evidence does not 

show glyphosate causes cancer.

When the IARC report was released, EPA was 

conducting its registration review of glyphosate, during 

which it examined various scientific studies, including those 

IARC considered. In 2017, EPA published its proposed 

conclusion: Glyphosate was not likely to be carcinogenic to 

humans. But, that same year, pursuant to Proposition 65, 
12 HARDEMAN V. MONSANTO

California law categorized glyphosate as a chemical known 

to the state to cause cancer. Cal. Off. of Env’t Health Hazard 

Assessment, Glyphosate, (“Glyphosate Proposition 65”), 

https://oehha.ca.gov/proposition-65/chemicals/glyphosate. 

That classification triggered a state law requirement to attach 

a warning label to glyphosate products. See id.; Cal. Health 

& Safety Code § 25249.6.

In April 2019—one month after the jury verdict in this 

case—EPA noted that commenters “expressed concerns that 

glyphosate formulations are more toxic than glyphosate 

alone.” Proposed Interim Registration Review at 10. EPA 

explained that “there are few research projects that have 

attempted to directly compare technical grade glyphosate to 

the formulations under the same experimental design,” but 

“[i]f at any time, information becomes available that 

indicates adverse human health effects of concern for 

exposure to glyphosate or its formulations, EPA intends to 

review it and determine the appropriate regulatory action.” 

Id. at 11.

About five months after the jury verdict, EPA issued a 

letter to all registrants of glyphosate-containing products. 

Letter from Michael L. Goodis, EPA, Office of Pesticide 

Programs (Aug. 7, 2019) (“2019 letter”). The 2019 letter 

was not the product of any formal proceeding, was not 

published in the Federal Register, did not cite any new 

scientific findings, and took no position on whether 

Roundup causes cancer. Instead, this letter challenged 

California’s inclusion of glyphosate in Proposition 65 as 

contrary to “EPA’s determination that glyphosate is ‘not 

likely to be carcinogenic to humans.’” Id. at 1. Given this 

determination, EPA “considers the Proposition 65 warning 

language” that glyphosate is carcinogenic “to constitute a 

false and misleading statement” that violates FIFRA’s 
HARDEMAN V. MONSANTO 13

prohibition against “misbranded” substances. Id. 1–2 (citing 

§ 136(q)(1)(A)). The letter concluded with EPA instructing 

registrants to remove such warning statements from labels of 

glyphosate-based pesticides. Id. at 2.

B

In 2016, Hardeman sued Monsanto alleging that his use 

of Roundup—which started in the 1980s and ended in 

2012—led to his diagnosis of non-Hodgkin’s lymphoma 

(“NHL”) in early 2015. Hardeman’s case is one of 

approximately 5,000 in federal court alleging that Roundup 

causes NHL. The Judicial Panel on Multidistrict Litigation 

consolidated those cases for pretrial proceedings in the 

Northern District of California. Hardeman’s case was the 

first of these consolidated cases to go to trial.

NHL is a cancer that affects white blood cells in the 

immune system. Approximately 70% or more of NHL cases 

are idiopathic, meaning they develop for unknown reasons. 

However, some causes of NHL—such as hepatitis C 

(“HCV”)—are well established. Hardeman had HCV for 

25 to 40 years before developing NHL.

Hardeman alleged Monsanto’s failure to warn him of the 

carcinogenic risks of Roundup caused his NHL. Monsanto 

moved to dismiss, arguing that Hardeman’s claims were 

preempted by FIFRA given EPA’s registration of 

glyphosate, approval of the Roundup label, and 

classification of glyphosate as non-carcinogenic. The 

district court denied Monsanto’s motion. Monsanto raised 

preemption again in a motion for summary judgment, which 

the district court likewise denied.

The district court bifurcated the pretrial proceedings. 

The first phase addressed “general causation”—whether
14 HARDEMAN V. MONSANTO

glyphosate can cause NHL at exposure levels humans might 

experience. The second phase addressed “specific 

causation”—whether Hardeman’s exposure to Roundup 

caused his NHL.

The district court granted in part and denied in part 

Monsanto’s motion to exclude Hardeman’s general 

causation experts, allowing three of Hardeman’s experts to 

testify—Dr. Portier, Dr. Ritz, and Dr. Weisenburger. These 

experts introduced their general causation opinions with 

scientific evidence from epidemiology (study of disease in 

human populations), toxicology (animal studies), and 

genotoxicology (cell studies); applied the Bradford Hill 

criteria;2 and used meta-analyses that combined and 

analyzed the results of case-control studies.

The district court, however, acknowledged that 

significant problems with Hardeman’s experts’ analyses 

made it a “very close question” whether their testimony was 

admissible to support general causation. In re Roundup 

Prods. Liab. Litig., 390 F. Supp. 3d 1102, 1108 (N.D. Cal. 

2018). The district court interpreted the Ninth Circuit’s 

approach to Daubert as requiring “slightly more room for 

deference to experts in close cases than might be appropriate 

in some other Circuits.” Id. at 1113 (citations omitted). 

Ultimately, the district court concluded Hardeman’s three 

2 The Bradford Hill criteria are nine factors generally accepted as 

relevant to assessing causation, such as: (1) the strength of the 

association; (2) consistency; (3) specificity; (4) temporality; 

(5) biological gradient or dose response; (6) biological plausibility; 

(7) coherence with other scientific knowledge; (8) experimental 

evidence; and (9) analogy. See In re Roundup Prods. Liab. Litig., 390 F. 

Supp. 3d 1102, 1116 (N.D. Cal. 2018) (citing Austin Bradford Hill, The 

Environment and Disease: Association or Causation?, 58 Proceedings 

of the Royal Society of Medicine 295 (1965)).
HARDEMAN V. MONSANTO 15

experts’ opinions were relevant and reliable, satisfying 

Federal Rule of Evidence 702 and Daubert.

The district court later denied Monsanto’s motion to 

exclude Hardeman’s specific causation experts. 

Hardeman’s experts performed differential diagnosis, a 

methodology by which a physician “rules in” all potential 

causes of a disease, “rules out” those for “which there is no 

plausible evidence of causation, and then determines the 

most likely cause among those that cannot be excluded.” 

Wendell v. GlaxoSmithKline LLC, 858 F.3d 1227, 1234 (9th 

Cir. 2017). Hardeman’s experts considered various risk 

factors beyond Roundup exposure that could explain his 

disease, including age, race, obesity, hepatitis B (“HBV”), 

and HCV, as well as idiopathic origin—i.e., no known cause. 

They concluded Roundup caused Hardeman’s NHL by 

ruling in Roundup based on general causation expert 

opinions and ruling out HCV and idiopathy3 as causes of 

Hardeman’s NHL. The district court admitted the experts’ 

opinions, noting this circuit affords experts “wide latitude in 

how they practice their art when offering causation 

opinions.” In re Roundup, 358 F. Supp. 3d at 960 (citing 

Wendell, 858 F.3d at 1237).

Monsanto requested a bifurcated trial, with the first 

phase addressing whether Roundup caused Hardeman’s 

cancer (without reference to any regulatory decisions 

regarding glyphosate or Roundup) and the second phase 

3 As to idiopathy, the district court held that “[i]t is sufficient for a 

qualified expert, in reliance on his clinical experience, review of a 

plaintiff[’s] medical records, and evaluation of the general causation 

evidence, to conclude that an ‘obvious and known risk factor[]’ is the 

cause of that plaintiff’s disease.” In re Roundup Prods. Liab. Litig., 

358 F. Supp. 3d 956, 960 (N.D. Cal. 2019) (quoting Wendell, 858 F.3d 

at 1235).
16 HARDEMAN V. MONSANTO

addressing liability and damages (where the jury could see 

some of that evidence). Monsanto moved to exclude all 

evidence regarding IARC’s report, which detailed the 

agency’s classification of glyphosate as probably 

carcinogenic, as irrelevant and likely to confuse and distract 

the jury. But if IARC evidence were admitted, Monsanto 

argued, the district court should admit evidence that 

numerous regulatory agencies around the world concluded 

that glyphosate is safe.

Ultimately, the district court excluded IARC’s report but 

admitted IARC’s classification of glyphosate as probably 

carcinogenic to mitigate the prejudice caused to Hardeman 

due to bifurcation of the trial. The district court also 

admitted conclusions from EPA, EFSA, and ECA that 

glyphosate was safe but excluded conclusions from other 

regulatory bodies as cumulative.

At trial, Hardeman’s experts testified that his exposure 

to glyphosate caused his NHL. Monsanto’s experts testified 

that little evidence links glyphosate to cancer in humans and 

that Hardeman’s HCV most likely caused his cancer or his 

cancer was idiopathic.

The district court issued a “substantial factor” causation 

instruction. The jury was instructed that, to rule for 

Hardeman, it must find that glyphosate exposure was a butfor cause of his cancer or one of two or more factors that 

independently could have caused his cancer.

After Phase One (on causation), the jury returned a 

verdict that Roundup exposure was a “substantial factor” in 

causing Hardeman’s NHL. After Phase Two (on liability 

and damages), the jury found that Monsanto failed to warn 

about Roundup’s NHL risk and Hardeman was entitled to 

punitive damages. The jury awarded Hardeman 
HARDEMAN V. MONSANTO 17

$5,267,634.10 in compensatory damages and $75 million in 

punitive damages.

In post-trial motions, Monsanto argued that the district 

court improperly excluded evidence of foreign regulatory 

approvals of glyphosate, which allegedly deprived the jury 

of the scope of evidence reinforcing Monsanto’s view of the 

science. The district court explained that such evidence 

about foreign regulators would have been cumulative under 

Federal Rule of Evidence 403 and denied Monsanto’s 

motion to overturn the verdict and for judgment as a matter 

of law. But the district court reduced the punitive damages 

award of $75 million to $20 million. These appeals 

followed.

II

Whether Hardeman’s state claims are preempted is 

reviewed de novo. Nathan Kimmel, Inc. v. DowElanco, 

275 F.3d 1199, 1203 (9th Cir. 2002). Monsanto argues that 

Hardeman’s failure-to-warn claims are preempted by 

FIFRA, under which states cannot “impose . . . any 

requirements for labeling or packaging in addition to or 

different from” the requirements in FIFRA itself. § 136v(b) 

(emphasis added); see also U.S. Const. art. VI, cl. 2 (federal 

law “shall be the supreme Law of the Land . . . any Thing in 

the Constitution or Laws of any State to the Contrary 

notwithstanding”). We conclude that Hardeman’s failureto-warn claims based on Roundup’s labeling are consistent 

with FIFRA and thus are neither expressly nor impliedly 

preempted.

A

FIFRA does not expressly preempt Hardeman’s claims 

because FIFRA’s requirement that a pesticide not be 
18 HARDEMAN V. MONSANTO

misbranded is consistent with, if not broader than, 

California’s common law duty to warn. Bates employs a 

two-part test to determine whether FIFRA preempts a state 

law claim. 544 U.S. at 444. First, the state law must be a 

requirement “for labeling or packaging.” Id. (quoting 

§ 136v(b)). Second, the state law must impose a labeling or 

packaging requirement that is “in addition to or different 

from” those required under FIFRA. Id. (quoting § 136v(b)). 

Because Hardeman’s complaint is based on Monsanto’s 

failure to provide an adequate warning on a label under 

California law, part one of this test is satisfied.

As to part two of the Bates test, “a state-law labeling 

requirement is not pre-empted by § 136v(b) if it is equivalent 

to, and fully consistent with, FIFRA’s misbranding 

provisions.” 544 U.S. at 447. State law is “equivalent to” 

and “fully consistent with” FIFRA where both impose 

“parallel requirements,” meaning that a violation of the state 

law is also a violation of FIFRA. Id.; see also id. at 454 

(“[A] manufacturer should not be held liable under a state 

labeling requirement subject to § 136v(b) unless the 

manufacturer is also liable for misbranding as defined by 

FIFRA.”). Thus, if a violation of California’s duty to warn 

would also be a violation of FIFRA’s misbranding provision, 

then they impose parallel requirements fully consistent with 

each other. Id. at 454 (“To survive pre-emption, the statelaw requirement need not be phrased in the identical

language as its corresponding FIFRA requirement . . . .”). 

To that end, elements of California’s duty to warn and 

FIFRA’s misbranding provision are compared below.

FIFRA’s misbranding provision requires a pesticide 

label “contain a warning or caution statement which may be 

necessary and if complied with . . . is adequate to protect 

health and the environment.” § 136(q)(1)(G). Similarly, 
HARDEMAN V. MONSANTO 19

California common law requires a manufacturer to warn 

either of any health risk4 that is “known or knowable” (in

strict liability) or those risks “a reasonably prudent 

manufacturer would have known and warned about” (in

negligence). Conte v. Wyeth, Inc., 85 Cal. Rptr. 3d 299, 310 

(Ct. App. 2008). Thus, FIFRA—which requires a warning 

“necessary” and “adequate to protect health”—is broader 

than California’s requirement under negligence (no warning 

needed if unreasonable to do so)5 and is, at minimum, 

consistent with California’s requirement under strict liability 

(no warning needed if risk not known or knowable). See id.; 

§ 136(q)(1)(G). Because FIFRA’s misbranding 

requirements parallel those of California’s common law 

duty, Hardeman’s failure-to-warn claims effectively enforce 

FIFRA’s requirement against misbranding and are thus not 

expressly preempted. See § 136(q)(1)(G); Bates, 544 U.S. 

at 447–48 (citing favorably Justice O’Connor’s explanation 

in Medtronic, 518 U.S. 470, that “a state cause of action that 

seeks to enforce a federal requirement ‘does not impose a 

requirement that is “different from, or in addition to,” 

requirements under federal law’”).

4 Because a risk of cancer is a risk contemplated by FIFRA as 

“necessary” and “adequate to protect health,” § 136(q)(1)(G), (x), (bb), 

we need not address the possibility that California common law may 

require a manufacturer to warn of a risk not contemplated by FIFRA’s 

misbranding provision.

5 Though “it may be necessary as a matter of [state] law to prove 

that th[e] violations were the result of negligent conduct . . . such 

additional elements of the state-law cause of action would make the state 

requirements narrower, not broader, than the federal requirement. While 

such a narrower requirement might be ‘different from’ the federal rules 

in a literal sense, such a difference would surely provide a strange reason 

for finding pre-emption of a state rule insofar as it duplicates the federal 

rule.” Medtronic, Inc. v. Lohr, 518 U.S. 470, 495 (1996).
20 HARDEMAN V. MONSANTO

Monsanto, however, argues that because EPA repeatedly 

registered Roundup for sale without a cancer warning on the 

label, a jury’s decision that Roundup should include such a 

warning would effectively impose a requirement “in 

addition to or different from” that required by FIFRA, and 

so the state law is preempted. Granted, EPA is highly 

involved in the pesticide registration process, which includes 

approval of product labels. And EPA will not register a 

pesticide unless it determines that the label “compl[ies] 

with” FIFRA’s “requirements.” § 136a(c)(5)(B). But this 

argument misses the point for two reasons.

First, EPA’s approval of a label—one step in a larger 

registration process—is not conclusive of FIFRA 

compliance. FIFRA specifies:

In no event shall registration of an article be 

construed as a defense for the commission of 

any offense under this subchapter. As long 

as no cancellation proceedings are in effect 

registration of a pesticide shall be prima facie 

evidence that the pesticide, its labeling and 

packaging comply with the registration 

provisions of the subchapter.

§ 136a(f)(2) (emphasis added).6 Because EPA has not 

instituted any cancellation proceedings against Monsanto, 

6 Section 136a(f)(2) distinguishes this case from Riegel v. 

Medtronic, Inc., 552 U.S. 312 (2008), which held that the Medical 

Device Amendments (“MDA”) to the Federal Food, Drug, and Cosmetic 

Act (“FDCA”) expressly preempted claims challenging the safety and 

effectiveness of a medical device that received premarket approval from 

the Food and Drug Administration (“FDA”). Id. at 315, 330. Like 

FIFRA’s preemption provision, the MDA preempts certain state 

requirements that are different from, or in addition to, certain federal 
HARDEMAN V. MONSANTO 21

EPA’s approval of Roundup’s label is prima facie evidence 

of FIFRA compliance. See id. And looking at FIFRA 

holistically, this makes sense—if mere EPA approval of a 

label were determinative of FIFRA compliance, then 

FIFRA’s misbranding provision and regulations imposing a 

duty to report “additional factual information regarding 

unreasonable adverse effects” would serve no purpose. 

§ 136d(a)(2); see also § 136(q)(1) (detailing when a 

pesticide is misbranded); 40 C.F.R. § 159.152 (imposing 

duty to report additional information on adverse effects). So 

even though EPA approved Roundup’s label, a judge or jury 

could disagree and find that same label violates FIFRA. And 

because EPA’s labeling determinations are not dispositive of 

FIFRA compliance, they similarly are not conclusive as to 

which common law requirements are “in addition to or 

different from” the requirements imposed by FIFRA. See 

§ 136v(b); cf. Bates, 544 U.S. at 451 (“Private remedies that 

enforce federal misbranding requirements would seem to 

aid, rather than hinder, the functioning of FIFRA.”); Indian 

Brand Farms, Inc. v. Novartis Crop Prot. Inc., 617 F.3d 207, 

222 (3d Cir. 2010) (explaining that Bates “established that 

mere inconsistency between the duty imposed by state law 

and the content of a manufacturer’s labeling approved by the 

EPA at registration did not necessarily mean that the state 

law duty was preempted”).

Second, the EPA actions that Monsanto alleges preempt 

Hardeman’s claims do not carry the force of law. As noted 

in Bates, “[a] requirement is a rule of law that must be 

obeyed.” 544 U.S. at 445. To establish requirements that 

requirements. See 21 U.S.C. § 360k(a)(1). But the MDA does not 

contain a provision like FIFRA’s § 136a(f)(2), which clarifies that the 

agency’s approval of a label is not determinative of compliance with the 

statute.
22 HARDEMAN V. MONSANTO

can preempt state law under § 136v(b), agency action must 

have the force of law. See Wyeth v. Levine, 555 U.S. 555, 

576, 580 (2009). In other words, only where there is a 

relevant EPA action carrying the force of law are state 

failure-to-warn claims prohibited from imposing 

requirements inconsistent with that action.7 Monsanto tries 

to circumvent this caveat by arguing that although EPA’s 

approval of Roundup’s label was not a rulemaking, it 

happened “in the context of [a] registration process” that 

“has the hallmarks of formal agency action.” See § 136a; 

40 C.F.R. § 155.50(b)–(c). But, as explained above, FIFRA 

expressly states that EPA’s decision to approve a label 

during the registration process raises only a rebuttable 

presumption that the pesticide and its label comply with 

FIFRA. § 136a(f)(2). It would defy logic to say a rebuttable 

presumption carries the force of law necessary to have 

preemptive effect, as doing so would deny any ability to 

rebut the presumption.

Nor does EPA’s 2019 letter, sent after the conclusion of 

Hardeman’s trial to all registrants of products containing 

glyphosate, carry the force of law. Generally, “Congress 

contemplates administrative action with the effect of law 

when it provides for a relatively formal administrative 

procedure tending to foster the fairness and deliberation that 

7 Monsanto relies on Bates’s explanation that a failure-to-warn 

claim alleging that a label should have stated “DANGER” instead of 

“CAUTION” would be preempted “because it is inconsistent with 

40 C.F.R. § 156.64 (2004), which specifically assigns these warnings to 

particular classes of pesticides based on their toxicity.” 544 U.S. at 453. 

But this example deals with agency action that has the force of law—

FIFRA regulation 40 C.F.R. § 156.64. Here, however, neither EPA’s 

approval of Roundup’s label during registration nor EPA’s 2019 letter 

carriesthe force of law necessary to preempt Hardeman’s failure-to-warn 

claims.
HARDEMAN V. MONSANTO 23

should underlie a pronouncement of such force.” United 

States v. Mead Corp., 533 U.S. 218, 230 (2001). But the 

2019 letter—stating that EPA believes any pesticide label 

with a cancer warning due to the presence of glyphosate will 

be misbranded—did not follow any “formal administrative 

procedure” that would give the letter the force of law.8 See 

id. The 2019 letter was issued without any written notice, 

gave no hearing or opportunity to respond, and lacked any 

sort of dispute-resolution process. See Merck Sharp & 

Dohme Corp. v. Albrecht, 139 S. Ct. 1668, 1679 (2019). 

Instead, the 2019 letter is similar to the letter in Fellner v. 

Tri-Union Seafoods, LLC, which lacked preemptive effect 

because the FDA “merely expressed an informal policy 

opinion in a letter, and it did so only after [the plaintiff’s] 

injuries were allegedly suffered.” 539 F.3d 237, 255 (3d Cir. 

2008).9

8 EPA’s 2017 determination that glyphosate is not carcinogenic does 

not magically give the “force of law” to this 2019 letter on misbranding. 

EPA’s 2017 determination was given in the context of glyphosate 

“undergoing Registration Review” after evaluating glyphosate’s 

carcinogenic potential. EPA, Revised Glyphosate Issue Paper: 

Evaluation of Carcinogenic Potential 12 (Dec. 2017) (“Registration 

Review also allows the agency to incorporate new science.”). Even if 

the 2017 determination stems from more formal procedures, it is not 

necessarily at odds with the future failure-to-warn claim because it was 

made as part of EPA’s registration decision, which only supports 

presumptive (not conclusive) compliance with FIFRA. See § 136a(f)(2).

9 In contrast, EPA’s cancellation proceedings, for example, may 

have the force of law given that § 136d(b) lays out a formal notice and 

hearing process, and no comparable prima facie evidence restriction 

applies. See § 136a(f)(2) (stating that registration is “prima facie 

evidence” of FIFRA compliance “[a]s long as no cancellation 

proceedings are in effect”). But no cancellation proceedings were in 

effect here.
24 HARDEMAN V. MONSANTO

Thus, we affirm the district court’s conclusion that 

Hardeman’s state failure-to-warn claims are “equivalent to” 

and “fully consistent with” FIFRA and therefore not 

expressly preempted. See Bates, 544 U.S. at 449 (“The long 

history of tort litigation against manufacturers of poisonous 

substances adds force to the basic presumption against preemption. If Congress had intended to deprive injured parties 

of a long available form of compensation, it surely would 

have expressed that intent more clearly.”). The Supreme 

Court decided Bates over fifteen years ago, and regulatory 

preemption in other contexts has developed considerably in 

the interim. For FIFRA preemption, however, currently 

Bates controls.

B

Because Monsanto could comply with both FIFRA and 

California law, FIFRA did not impliedly preempt 

Hardeman’s state failure-to-warn claims.

1

A state failure-to-warn claim is impliedly preempted if 

the relevant federal and state laws “irreconcilably conflict.” 

Merck, 139 S. Ct. at 1679 (quoting Rice v. Norman Williams 

Co., 458 U.S. 654, 659 (1982)). “[S]tate and federal law 

conflict where it is impossible for a private party to comply 

with both state and federal requirements.” PLIVA, Inc. v. 

Mensing, 564 U.S. 604, 618 (2011) (internal quotation marks 

and citation omitted). To demonstrate an “irreconcilabl[e] 

conflict,” Monsanto must present “clear evidence” that 

(1) the agency was “fully informed” of “the justifications for 

the warning” the plaintiff demands, (2) the agency has 

“informed the . . . manufacturer that [it] would not approve 

changing the . . . label to include that warning,” and (3) the 

agency’s action “carr[ies] the force of law.” Merck, 139 S. 
HARDEMAN V. MONSANTO 25

Ct. at 1678–79. However, because EPA’s actions—such as 

registering Roundup, approving Roundup’s label, and 

issuing the 2019 letter—do not have the force of law, 

Monsanto fails part (3) of Merck’s “clear evidence” of 

“irreconcilabl[e] conflict” test and cannot show preemption. 

See supra Section II.A.

2

Monsanto also argues that Hardeman’s claims are 

impliedly preempted because, under EPA’s regulations, 

Monsanto could not have unilaterally changed Roundup’s 

label, making it impossible for Monsanto to comply with 

both FIFRA and California’s common law duty to warn. 

Monsanto relies primarily on PLIVA, a case concerning the 

federal regulatory scheme governing generic drugs. 

564 U.S. 604. But, as explained in PLIVA, “different federal 

statutes and regulations may . . . lead to different preemption results.” Id. at 626. Here, FIFRA’s regulatory 

regime for pesticides differs meaningfully from the 

regulatory scheme governing generic drugs in PLIVA and, as 

a result, Monsanto’s implied preemption argument fails.

Under the regulatory scheme at issue in PLIVA, generic 

drug manufacturers have an “ongoing federal duty of 

sameness,” according to which they must use the same 

labeling as the corresponding name-brand drug. Id. at 613 

(internal quotation marks and citations omitted). Generic 

drug manufacturers do not draft their products’ initial 

labeling and do not have the power to revise labeling. See 

id. As the Supreme Court explained, “[i]f [the generic drug 

manufacturers] had [asked the FDA for help], and if the FDA 

decided there was sufficient supporting information, and if 

the FDA undertook negotiations with the brand-name 

manufacturer, and if adequate label changes were decided on 

and implemented, then the [generic drug] [m]anufacturers 
26 HARDEMAN V. MONSANTO

would have started a Mouse Trap game that eventually led 

to a better label.” Id. at 619. But, in PLIVA, the generic drug 

manufacturer could not “independently satisfy . . . state 

duties for pre-emption purposes” because it “cannot satisfy 

its state duties without the Federal Government’s special 

permission and assistance, which is dependent on the 

exercise of judgment by a federal agency.” Id. at 623–24 

(explaining that “[t]he only action the [generic drug] 

[m]anufacturers could independently take” was “asking for 

the FDA’s help”).

Unlike the FDCA and FDA regulatory scheme for 

generic drug manufacturers, FIFRA and the EPA regulatory 

scheme provide that pesticide manufacturers are responsible 

for drafting their own product labels, § 136a(c)(1)(C), and 

do not need to maintain the same labeling as another 

manufacturer. Once a pesticide is registered, the 

manufacturer has a “continuing obligation to adhere to 

FIFRA’s labeling requirements.” Bates, 544 U.S. at 438 

(citations omitted). When a label needs to be changed, the 

manufacturer has the responsibility to change the label by 

drafting and submitting the label to EPA for approval, 

40 C.F.R. § 152.50(e), which EPA “shall” approve if it 

determines the change will not violate FIFRA, § 136a(f)(1). 

This is a far cry from the “special permission and assistance” 

needed from the FDA in PLIVA to change a generic drug 

label, a process constrained by a duty of sameness and the 

added step of agency deliberations with name-brand 

manufacturers. See 564 U.S. at 623–24.

Moreover, EPA permits pesticide manufacturers to make 

certain changes to labels without prior approval. See id.

at 623. Specifically, manufacturers can make minor 

modifications to labeling without prior EPA approval if EPA 

is notified of the change. 40 C.F.R. § 152.46(a); EPA, 
HARDEMAN V. MONSANTO 27

Office of Pesticide Programs, Pesticide Registration Notice 

98-10 (Oct. 22, 1998) (“PRN 98-10”). Thus, unlike the 

generic drug manufacturers in PLIVA, pesticide 

manufacturers “can act sufficiently independently under 

federal law” when amending a label. See PLIVA, 564 U.S. 

at 623.

Though Monsanto contends that “[a]dding a warning 

about cancer would hardly qualify as a ‘minor 

modification,’” EPA has repeatedly permitted pesticide 

manufacturers to use the notification procedure to add 

notices related to cancer to their products’ labels.10 

Nevertheless, Monsanto counters that there is no “single 

example where EPA has allowed a registrant to use the 

notification process” where EPA previously “found the 

relevant chemical was not carcinogenic, much less where it 

determined a cancer warning would render a label false and 

misleading,” referring to the 2019 letter.

But neither EPA’s 2017 finding that glyphosate is not 

carcinogenic nor the 2019 letter (which do not carry the force 

of law) divert Monsanto to a different process for amending 

10 For instance, pursuant to PRN 98-10, pesticide manufacturer 

Bayer CropScience notified EPA “of a minor labeling amendment for 

LARVIN Technical,” informing EPA that “[a]s required by California 

Proposition 65, the following statement has been added to the label, ‘This 

product contains a chemical known to the state of California to cause 

cancer.’” Letter from Larry R. Hodges, Registration Manager, Bayer 

CropScience, to EPA, Office of Pesticide Programs 4 (Nov. 29, 2012), 

www3.epa.gov/pesticides/chem_search/ppls/000264-00343-20131217.

pdf. In response, EPA’s Registration Division “conducted a review of 

this request for its applicability under PRN 98-10 and finds that the 

action(s) requested fall within the scope of PRN 98-10.” Letter from 

Jennifer Gaines, EPA, Office of Pesticide Programs, to Larry Hodges,

Bayer CropScience 2 (Dec. 17, 2012), www3.epa.gov/pesticides/chem_

search/ppls/000264-00343-20131217.pdf.
28 HARDEMAN V. MONSANTO

a label beyond those normally followed by pesticide 

manufacturers under FIFRA and its regulations, as described 

above. Considering the responsibility FIFRA places on 

manufacturers to update pesticide labels and that EPA has 

allowed pesticide manufacturers to add cancer warnings to 

labels through the notification process without prior 

approval, it is not impossible for Monsanto to add a cancer 

warning to Roundup’s label. See PLIVA, 564 U.S. at 623; 

see also Wyeth, 555 U.S. at 573 (explaining that 

“[i]mpossibility pre-emption is a demanding defense”).

III

Whether the district court applied the correct legal 

standard under Daubert is reviewed de novo, and the district 

court’s decision to admit expert testimony is reviewed for 

abuse of discretion. Estate of Barabin v. AstenJohnson, Inc., 

740 F.3d 457, 462 (9th Cir. 2014) (en banc), overruled on 

other grounds by United States v. Bacon, 979 F.3d 766 (9th 

Cir. 2020) (en banc). We hold that the district court 

ultimately applied the correct legal standard under Daubert

and did not abuse its discretion by admitting Hardeman’s 

general and specific causation expert testimony.

A

Under Federal Rule of Evidence 702, expert testimony 

must be reliable to be admissible. Daubert, 509 U.S. at 589. 

Scientific evidence is reliable when “the principles and 

methodology used by an expert are grounded in the methods 

of science.” Clausen v. M/V New Carissa, 339 F.3d 1049, 

1056 (9th Cir. 2003). When determining reliability, district 

court judges can consider the following non-exclusive 

factors: (1) “whether the theory or technique employed by 

the expert is generally accepted in the scientific 

community;” (2) “whether it’s been subjected to peer review 
HARDEMAN V. MONSANTO 29

and publication;” (3) “whether it can be and has been tested;” 

and (4) “whether the known or potential rate of error is 

acceptable.” Daubert v. Merrell Dow Pharms., Inc., 43 F.3d 

1311, 1316 (9th Cir. 1995) (citing Daubert, 509 U.S. at 593–

95). “Th[is] inquiry is ‘flexible,’” Wendell, 858 F.3d at 1232 

(quoting Daubert, 509 U.S. at 594), and “should be applied 

with a ‘liberal thrust’ favoring admission,” Messick v. 

Novartis Pharms. Corp., 747 F.3d 1193, 1196 (9th Cir. 

2014) (quoting Daubert, 509 U.S. at 588).11

Monsanto contends that, by relying on a misguided 

reading of Wendell and Messick, the district court 

misinterpreted Daubert to be more forgiving of experts’ 

extrapolations than this circuit allows. But, in reaching its 

conclusions, the district court followed this court’s 

precedent and thus cannot be faulted for following binding 

case law. Monsanto’s specific critiques are addressed 

below.

First, according to Monsanto, the district court 

erroneously stated there is “slightly more room for deference 

to experts” in close cases, In re Roundup, 390 F. Supp. 3d 

at 1113, and that courts in this circuit are “more tolerant of 

11 This liberal thrust favoring admission is not without limits. “Just 

as the district court cannot abdicate its role as gatekeeper, so too must it 

avoid delegating that role to the jury.” Estate of Barabin, 740 F.3d at 464 

(holding that district court erred by “pass[ing] its greatest concern about 

[the expert’s] testimony to the jury to determine” and there was little 

“indication that the district court assessed, or made findings regarding, 

the scientific validity or methodology of [another expert’s] proposed 

testimony”); see also United States v. Valencia-Lopez, 971 F.3d 891, 899 

(9th Cir. 2020) (holding that district court erred in admitting expert 

testimony without making a reliability determination by dismissing the 

expert’s deficiencies as “going to the weight, not admissibility, of [the 

expert’s] testimony” (quoting Nease v. Ford Motor Co., 848 F.3d 219, 

230 (4th Cir. 2017))).
30 HARDEMAN V. MONSANTO

borderline expert opinions,” In re Roundup, 358 F. Supp. 3d 

at 959.

As an initial matter, this court is not an outlier following 

a more flexible Daubert approach than other circuits. The 

cases on which the district court relied do not establish 

otherwise. For instance, in the Fourth Circuit case relied on 

by the district court, the expert failed to provide a proper 

scientific basis for her differential diagnosis by “focus[ing] 

almost exclusively on the fact that [plaintiff] took the drug 

and later developed the disease, rather than explaining what 

led her to believe that it was a substantial contributing factor 

as compared to other possible causes.” In re Lipitor 

(Atorvastatin Calcium) Mktg., Sales Pracs. & Prods. Liab. 

Litig., 892 F.3d 624, 645 (4th Cir. 2018). But if we compare 

the expert in Lipitor to, for instance, the expert in Messick, 

the cases are readily distinguishable. Unlike the Lipitor 

expert, the expert in Messick provided a scientific basis for 

his conclusion by “refer[ing] to his own extensive clinical 

experience as the basis for his differential diagnosis, as well 

as his examination of [plaintiff’s] records, treatment, and 

history.” 747 F.3d at 1198.

Similarly, in the Sixth Circuit case relied on by the 

district court, the expert’s causation analysis was insufficient 

because literature had only hypothesized but did not find a 

link between the chemical and disease. Tamraz v. Lincoln 

Elec. Co., 620 F.3d 665, 677–78 (6th Cir. 2010). The 

Tamraz court explained, “the problem is not that [the expert] 

failed to cite studies about [the chemical] causing [the 

disease] . . . or could not quantify how much [of the 

chemical] would lead to how much [of the disease]; the 

problem is that he failed to cite any non-speculative evidence 

for his conclusion.” Id. at 674. In contrast, the experts in 

Wendell did not present that deficiency, as they “relied not 
HARDEMAN V. MONSANTO 31

just on . . . studies—which not only examined reported cases 

but also used statistical analysis to come up with risk rates—

but also on their own wealth of experience and additional 

literature.” 858 F.3d at 1236. Thus, the Fourth Circuit and 

Sixth Circuit cases on which the district court relied are not 

at odds with this court’s Daubert approach.

To the extent the district court relied on In re Zoloft 

(Sertraline Hydrochloride) Products Liability Litigation, 

858 F.3d 787, 800 (3d Cir. 2017), and McClain v. Metabolife 

International, Inc., 401 F.3d 1233, 1244–45 (11th Cir. 

2005), to show those courts adopted the any step 

principles,12 those cases do not reveal a more flexible 

Daubert approach in this circuit. We have explained that

“expert evidence is inadmissible where the analysis is the 

result of a faulty methodology or theory as opposed to 

imperfect execution of laboratory techniques whose 

theoretical foundation is sufficiently accepted in the

scientific community to pass muster under Daubert.” City 

of Pomona v. SQM N. Am. Corp., 750 F.3d 1036, 1047–48 

(9th Cir. 2014) (internal quotation marks and citation 

omitted). Imperfect application of methodology may not 

render expert testimony unreliable because “‘[a] minor flaw 

in an expert’s reasoning or a slight modification of an 

otherwise reliable method’ does not render expert testimony 

inadmissible.” Id. at 1048 (quoting Amorgianos, 303 F.3d 

at 267 (adopting the any step principles)) (alteration in 

original). The reasoning guiding the any step principles is 

12 “The Daubert ‘requirement that the expert testify to scientific 

knowledge—conclusions supported by good grounds for each step in the 

analysis—means that any step that renders the analysis unreliable under 

the Daubert factors renders the expert’s testimony inadmissible.’” 

Amorgianos v. Nat’l R.R. Passenger Corp., 303 F.3d 256, 267 (2d Cir. 

2002) (quoting In re Paoli R.R. Yard PCB Litig., 35 F.3d 717, 745 (3d 

Cir. 1994)); see also Zoloft, 858 F.3d at 797; McClain, 401 F.3d at 1245.
32 HARDEMAN V. MONSANTO

not dissimilar; namely, “[t]he judge should only exclude the 

evidence if the flaw is large enough that the expert lacks 

‘good grounds’ for his or her conclusions.” Amorgianos, 

303 F.3d at 267 (quoting Paoli, 35 F.3d at 746).

Despite its incorrect assumption that this court is more 

permissive than others in admitting Daubert testimony, the 

district court still employed the correct legal standard for 

reliability when it admitted Hardeman’s expert testimony. 

For instance, the district court’s slight “deference to experts” 

with “borderline . . . opinions” was proper under Daubert: 

“[T]he interests of justice favor leaving difficult issues in the 

hands of the jury and relying on the safeguards of the 

adversary system . . . to ‘attack[] shaky but admissible 

evidence.’” Wendell, 858 F.3d at 1237 (quoting Daubert, 

509 U.S. at 596) (alteration in original). The Supreme Court 

has not directed courts to follow a different rule since it first 

decided Daubert almost 28 years ago.

Second, Monsanto takes issue with the district court’s 

suggestion that courts in this circuit can admit opinions “that 

lean strongly toward the ‘art’ side of the spectrum.” In re 

Roundup, 358 F. Supp. 3d at 959 (citation omitted). Though 

that may seem strange out of context, the district court was 

only reiterating our precedent following Daubert. See 

Messick, 747 F.3d at 1198 (“Medicine partakes of art as well 

as science . . . .”). The district court did not suggest that 

courts in this circuit allow “art” as a separate, standalone 

category divorced from logic and science. Rather, in 

referencing “art,” the district court followed Wendell and 

Messick’s instructions that a testifying expert can rely on his 

own extensive clinical experience under Daubert. See 

Wendell, 858 F.3d at 1237 (“Where, as here, two doctors 

who stand at or near the top of their field and have extensive 

clinical experience with the rare disease or class of disease 
HARDEMAN V. MONSANTO 33

at issue, are prepared to give expert opinions supporting 

causation, we conclude that Daubert poses no bar based on 

their principles and methodology.”); Messick, 747 F.3d 

at 1198 (allowing “extensive clinical experience” to form 

basis of differential diagnosis opinion).

Monsanto attempts to distinguish Wendell by arguing 

that it only allows experts to rely on clinical experience in 

exceptional circumstances not present here, particularly 

cases involving rare diseases with insufficient 

epidemiological data. Considering that Wendell drew the 

concept of “art” from Messick, a case which did not involve

a rare disease, we do not find that the application of art is 

limited to exceptional circumstances.

The district court allowed experts to rely on clinical 

experience, or “art,” only when conducting differential 

diagnosis to render specific causation opinions. Allowing 

experts to rely on clinical experience while conducting 

differential diagnosis, as the district court did here, is 

consistent with Messick. See 747 F.3d at 1198 (“[T]here is 

nothing wrong with a doctor relying on extensive clinical 

experience when making a differential diagnosis.”).

Monsanto further tries to distinguish Messick by 

emphasizing that the expert there relied on clinical 

experience as well as an examination of medical literature 

and plaintiff’s records. But Hardeman’s experts did the 

same thing here, if not more, by relying on epidemiological, 

animal, and cell studies. Acknowledging this, Monsanto 

counters that “there are numerous epidemiological studies 

on the association between glyphosate and Hardeman’s 

subtype of non-Hodgkin’s lymphoma that obviated the need 

for any reliance on ‘art.’” But Monsanto contradicts its own 

argument, asserting Wendell and Messick “state that 

experience can supplement reliable scientific studies and 
34 HARDEMAN V. MONSANTO

medical literature.” On this point, Monsanto is right: 

Hardeman’s experts’ clinical experience could supplement 

the epidemiological studies on which they relied.

Thus, the district court applied the correct legal standard 

under Daubert by following our precedent and fulfilling its 

“special obligation to determine the reliability of an expert’s 

testimony.” Elsayed Mukhtar v. Cal. State Univ., Hayward, 

299 F.3d 1053, 1063 (9th Cir. 2002) (internal quotation 

marks and citation omitted), overruled on other grounds by 

Estate of Barabin, 740 F.3d 457.

B

To establish general causation, Hardeman’s experts 

needed to show that glyphosate can cause NHL at exposure 

levels people realistically may have experienced. Here, 

Hardeman’s general causation experts relied on three types 

of studies: epidemiological,13 animal, and cellular. Animal 

studies are relevant evidence of causation where there is a 

sound basis for extrapolating conclusions from those studies 

to humans in real-world conditions. See Domingo ex rel. 

Domingo v. T.K., 289 F.3d 600, 606 (9th Cir. 2002). 

Similarly, cell studies can support more substantial evidence 

of causation. Therefore, animal and cell studies can help 

show causation so long as there is evidence of an association 

between glyphosate and NHL in humans within the 

epidemiological literature. This means that to be admissible 

testimony, the experts must have reliably based their general 

causation opinions on epidemiological evidence showing a 

13 Epidemiology is “the field of public health and medicine that 

studies the incidence, distribution, and etiology of disease in human 

populations.” Michael D. Green et al., Reference Guide on 

Epidemiology, in Reference Manual on Scientific Evidence 551, 551 (3d 

ed. 2011) (“Reference Manual”).
HARDEMAN V. MONSANTO 35

connection between glyphosate and cancer. As discussed 

below, the district court did not abuse its discretion in 

concluding that Hardeman’s experts satisfied this 

requirement.

Monsanto maintains that the experts did not use the 

epidemiological evidence reliably because they 

(1) dismissed the Agricultural Health Study (“AHS”) and 

(2) focused on case-control studies that did not sufficiently 

account for confounding factors. These criticisms, however, 

are not enough to render the expert opinions unreliable.

First, Monsanto criticizes Hardeman’s experts for 

ignoring the AHS, which Monsanto considers to be the most 

powerful evidence on the relationship between glyphosate 

and NHL. That study was a cohort study conducted by the 

National Institutes of Health that considered a range of 

pesticide exposures on 57,000 participants over several 

years. The AHS found no statistically significant association 

between glyphosate and NHL and showed no dose-response 

relationship, meaning “no evidence of higher rates of [NHL] 

with more days of exposure.”

Nonetheless, Hardeman’s experts had a reasonable basis 

for placing less weight on the AHS. For instance, an 

epidemiologist employed by Monsanto wrote years before 

the AHS results were announced that “the exposure 

assessment in the AHS will be inaccurate” because the AHS 

will have “spurious exposure-disease findings due to 

exposure misclassification.” Similarly, Monsanto’s 

toxicologist, Donna Farmer, recognized that “[m]any groups 

have been highly critical of the study as being a flawed 

study, in fact some have gone so far as to call it junk science 

. . . . [T]he bottom line is scary . . . there will be associations 

identified . . . just because of the way this study is designed.”
36 HARDEMAN V. MONSANTO

These criticisms from Monsanto employees resemble 

those from Hardeman’s experts that the AHS is flawed and 

unreliable. Though Monsanto changed its tune on the AHS 

because the misclassification concerns were allegedly 

addressed using “sensitivity analyses” as the study 

progressed, the overlapping criticisms still show that 

Hardeman’s expert opinions on the AHS are within “the 

range where experts might reasonably differ.” Kumho Tire 

Co. v. Carmichael, 526 U.S. 137, 153 (1999). Accordingly, 

the district court did not abuse its discretion in concluding 

that “the epidemiology evidence is open to different 

interpretations” such that “an expert who places more weight 

on the case-control studies than the AHS cannot be excluded 

as categorically unreliable for doing so.” In re Roundup, 

390 F. Supp. 3d at 1126.

Second, Monsanto criticizes Hardeman’s experts for 

relying on three case-control studies: De Roos (2003), 

McDuffie (2001), and Eriksson (2008), which allegedly 

contain serious flaws. Although case-control studies are 

“prone to recall bias,”14 Hardeman’s experts gave the district 

court valid reasons to discount this concern. For example, 

the experts explained that epidemiology studies overall 

found associations only between glyphosate and NHL, but 

not between glyphosate and other cancers asked about in the 

studies. The experts pointed out that, if participants were 

pre-disposed to think glyphosate caused cancer and 

consequently exhibited recall bias, the studies would have 

reported associations for glyphosate and other cancers. 

14 “[R]ecall bias[] occurs where people with a disease . . . are

differently able to recall past exposures than are people who never get 

sick; generally, the assumption is that the cases will recall greater levels 

of exposure, as those who become ill are more likely to ruminate about 

the possible causes of their disease.” Reference Manual at 585–86.
HARDEMAN V. MONSANTO 37

Hardeman’s experts also relied upon studies that sought to 

validate self-reports of pesticide exposure and found similar 

recall accuracy between controls and cases. Considering this 

evidence, the district court did not abuse its discretion in 

finding the “possible presence of recall bias” is “not 

significant enough to require an expert categorically to 

weight [the case-control studies] less heavily than the AHS.” 

In re Roundup, 390 F. Supp. 3d at 1133.

Monsanto criticizes the De Roos study specifically for 

“not properly account[ing] for [NHL’s] latency period” 

because the study analyzed data collected between 1979 and 

1986, but NHL takes “at least five to ten years to develop” 

and Roundup was put on the market in 1974. As the district 

court pointed out, a potential confounding variable15 is an 

important reason a study might show an association between 

glyphosate and NHL shortly after glyphosate was put on the 

market.

The De Roos study, however, reduced the risk of 

confounding by adjusting for many other pesticides. While 

Hardeman’s experts acknowledged that it is “always 

possible” that the observed association was the result of 

confounding not accounted for in De Roos, the adjustment 

for many other pesticides in De Roos made it “significantly 

less likely” that a pesticide other than glyphosate caused the 

observed association. As a result, the district court properly 

scrutinized the reliability of De Roos and did not abuse its 

discretion in concluding that, “at least for the studies that 

adjust for other pesticide exposures [i.e., De Roos], the 

relatively short period between glyphosate exposure and 

cancer development is not a concern so significant as to 

15 Confounding variables are other factors that could explain an 

observed association between a substance and the disease.
38 HARDEMAN V. MONSANTO

disqualify an expert who gives significant weight to the casecontrol studies in rendering a causation opinion.” In re 

Roundup, 390 F. Supp. 3d at 1123.

Nonetheless, Monsanto argues that Hardeman’s experts 

still did not sufficiently consider confounding factors while 

evaluating epidemiology. According to Monsanto, 

“McDuffie did not account for the effect of exposure to 

pesticides beyond glyphosate at all” and, “while Eriksson 

did provide some results adjusted for the effect of other 

pesticides, the adjusted results did not show a statistically 

significant link between glyphosate and [NHL].”

But while the district court acknowledged that 

“exclusive consideration of numbers unadjusted for other 

pesticides, when adjusted numbers are available, would be 

disqualifying,” In re Roundup, 390 F. Supp. 3d at 1140, 

Hardeman’s experts did not do that here. For instance, 

“Dr. Portier addressed the most significant concern—the 

possibility that pesticides other than glyphosate caused the 

observed cases of NHL—by focusing on data adjusted for 

potential confounding by various other pesticides.” In re 

Roundup, 390 F. Supp. 3d at 1133; see also id. at 1140–41, 

1143 (discussing Dr. Ritz and Dr. Weisenburger). Further, 

even where adjustment for other pesticides resulted in loss 

of statistical significance, the results still showed a positive 

association between glyphosate and NHL.16 Thus, contrary 

16 Monsanto criticizes Dr. Weisenburger for relying on a single 

favorable odds ratio from the “earliest iteration” of the North American 

Pooled Project. But such reliance is not enough to render 

Dr. Weisenburger’s entire testimony unreliable. See, e.g., Wendell, 

858 F.3d at 1233 (explaining that district courts should not look “too 

narrowly at each individual consideration, without taking into account 

the broader picture of the experts’ overall methodology”). The district 
HARDEMAN V. MONSANTO 39

to Monsanto’s criticisms, the general causation expert 

opinions were sufficiently supported by reliable 

epidemiological evidence, so admitting these experts’ 

testimony was not an abuse of discretion.

C

To establish specific causation, experts needed to show 

that Hardeman’s NHL was caused by glyphosate, rather than 

some other factor. To do so, Hardeman’s experts—

Dr. Weisenburger, Dr. Shustov, and Dr. Nabhan—used 

“differential diagnosis,” which starts with ruling in “all 

potential causes, then rul[ing] out the ones as to which there 

is no plausible evidence of causation, and then determin[ing] 

the most likely cause among those that cannot be excluded.” 

Wendell, 858 F.3d at 1234; see also Clausen, 339 F.3d 

at 1057. Here, Hardeman’s experts reliably used differential 

diagnosis because they ruled in glyphosate based on the 

epidemiological evidence supporting the general causation 

opinions and ruled out alternative causes, such as idiopathy 

and HCV.

1

Monsanto argues that Hardeman failed to adequately 

rule out idiopathy, considering that 70% or more of NHL 

cases have unknown causes. Monsanto acknowledges that 

an expert can rule out idiopathy by reliably concluding that 

the known factor (here, glyphosate) is a “substantial cause,” 

which can be shown when a strong association exists 

between the disease and that known risk factor. See Wendell, 

858 F.3d at 1235, 1237 (even though expert “was not entirely 

court properly considered this issue before concluding 

Dr. Weisenburger’s testimony was sufficiently reliable.
40 HARDEMAN V. MONSANTO

able to rule” out idiopathy, he could conclude a “known risk 

factor[]” was a substantial cause because “literature 

show[ed] that patients exposed to” the drugs in question 

were “at an increased risk for” the disease). But here, 

Monsanto argues that Hardeman’s experts did not reliably 

conclude that glyphosate was a substantial cause because no 

strong association existed between glyphosate and NHL, 

forcing the experts to rely on two flawed studies and their 

own subjective judgment.

Specifically, Monsanto argues that Hardeman’s experts 

did not rule in glyphosate as a substantial cause because, 

unlike the experts in Wendell, they did not show a sharp 

enough increased risk of cancer for those exposed to 

glyphosate. Monsanto focuses on Hardeman’s experts’ 

inability to present a study with an adjusted odds ratio 

above 2.0. But we have never suggested that a hardline 

increase in a risk statistic, or even an adjusted odds ratio 

above 2.0, is necessary for finding a strong association. See 

id. at 1234. To the contrary, flexibility is warranted 

considering the contextual nature of the Daubert inquiry. 

Thus, it was not an abuse of discretion to admit expert 

testimony—that glyphosate is a substantial cause—partly 

based on the epidemiological studies from the general 

causation opinions, where the general causation opinions 

showed a “robust connection between glyphosate and NHL.” 

In re Roundup, 358 F. Supp. 3d at 960.

Next, Monsanto criticizes Hardeman’s experts for 

relying on “two flawed studies”—McDuffie and Eriksson—

linking glyphosate and NHL. Monsanto focuses on the 

experts’ two attempted uses for those studies: (1) to assign a 

quantified risk to Hardeman based on the studies’ 

“unadjusted numbers” and (2) to show that Hardeman’s risk 

ratio must have exceeded 2.0 because he exceeded the 
HARDEMAN V. MONSANTO 41

exposure minimums from the two studies (i.e., two days per 

year or ten lifetime days of exposure). But this focus is 

misplaced. Though relying on McDuffie and Eriksson for 

those propositions may have been problematic, that is not 

what happened here. The district court explicitly considered 

these issues and properly exercised its gatekeeping function 

by precluding the experts from using the studies in those two 

ways.

Instead, the district court allowed Hardeman’s experts to 

rely on McDuffie and Eriksson to show a dose-response 

relationship between glyphosate and NHL. And 

Hardeman’s experts presented a sufficient basis for using 

these studies (though unadjusted for other pesticides) to 

show such a relationship. For instance, Dr. Weisenburger 

clarified, if a chemical “shows a dose response, it’s very 

likely an etiologic agent because it’s . . . unusual that a 

chemical would cause a disease and not have a dose 

response. So when you see a dose response, that gives you 

some assurance that it really is causing the disease.”

Had the experts relied only on McDuffie and Eriksson to 

show glyphosate is a substantial cause of NHL, their specific 

causation opinions may have been unreliable. However, 

Hardeman’s experts relied not only on McDuffie and 

Eriksson but also other epidemiological evidence (like De 

Roos) supporting a strong association, as well as their 

clinical experience and review of plaintiff’s medical records. 

Thus, as a whole, the evidence provided a sufficient basis for 

reliably ruling out idiopathy by concluding glyphosate was 

a substantial cause of Hardeman’s NHL. See Wendell, 

858 F.3d at 1233–34 (ruling out idiopathy for disease with 

70% idiopathy rate where expert relied on clinical 

experience, literature, and medical records).
42 HARDEMAN V. MONSANTO

2

Monsanto also argues that Hardeman’s experts did not 

reliably rule out HCV as an alternate cause. HCV is an 

established cause of NHL. Even though Hardeman was 

treated for HCV in 2005 and 2006, Monsanto claims that he 

was vulnerable to cellular damage caused by the virus for 

many years, including NHL. But, as Dr. Weisenburger 

explained, to cause cancer, the virus must be active, and 

there was no evidence that Hardeman’s HCV had been 

active for the decade preceding his NHL diagnosis. And this 

conclusion, as determined by the district court, had 

significant support in the scientific literature.

Further, Dr. Weisenburger’s underlying methodology 

for reaching this conclusion was sound. He relied on 

Hardeman’s medical records and his clinical experience and 

reviewed scientific literature (including seven studies) as the 

basis for ruling out HCV. See Messick, 747 F.3d at 1199 

(“[D]ifferential diagnosis grounded in significant clinical 

experience and examination of medical records and 

literature can certainly aid the trier of fact and cannot be 

considered to be offering ‘junk science.’”). Thus, 

Dr. Weisenburger reliably ruled out HCV as an alternate 

cause of Hardeman’s NHL, and the district court did not 

abuse its discretion in admitting Hardeman’s expert 

testimony on specific causation.

IV

 The district court’s decision to admit IARC’s 

glyphosate classification as a “probable carcinogen” but 

exclude contrary conclusions from other regulatory bodies is 

reviewed for abuse of discretion. Estate of Barabin, 

740 F.3d at 462. The district court made that decision to 
HARDEMAN V. MONSANTO 43

mitigate prejudice to Hardeman after granting Monsanto’s 

request to bifurcate the trial.

Monsanto argues that admitting IARC’s classification 

was an error because the classification’s minimal probative 

value was outweighed by unfair prejudice and juror 

confusion, which was allegedly exacerbated by the district 

court’s exclusion of various foreign regulatory agencies’ 

rejections of IARC’s classification. We disagree.

Under Rule 403, the district court can “exclude relevant 

evidence if its probative value is substantially outweighed by 

a danger of one or more of the following: unfair prejudice, 

confusing the issues, misleading the jury, undue delay, 

wasting time, or needlessly presenting cumulative 

evidence.” Fed. R. Evid. 403. “A district court’s Rule 403 

determination is subject to great deference, because the 

considerations arising under Rule 403 are susceptible only 

to case-by-case determinations, requiring examination of the 

surrounding facts, circumstances, and issues.” United States 

v. Hinkson, 585 F.3d 1247, 1267 (9th Cir. 2009) (en banc) 

(internal quotation marks and citation omitted).

According to Monsanto, IARC’s classification had 

minimal probative value because it did not rely on new data 

or gauge cancer risk from real-world glyphosate exposure. 

But this misses the point: IARC’s classification was 

admitted to mitigate prejudice to Hardeman from the trial’s 

bifurcation. Monsanto had specifically requested 

bifurcation to preclude evidence of its “attempting to 

influence regulatory agencies and manipulate public opinion 

regarding glyphosate.” Without IARC’s classification, 

“jurors w[ould] be left wondering, during the causation 

phase, how glyphosate could possibly be dangerous if it 

ha[d] gone largely unregulated for decades.” Further, the 

district court minimized the risk of prejudice to Monsanto by 
44 HARDEMAN V. MONSANTO

only admitting IARC’s classification, not the underlying 

details, and admitting the continued approval of glyphosate 

from three other regulators—EPA, EFSA, and ECA. 

Importantly, the district court instructed the jury to “not 

defer” to the conclusions of any of these regulatory bodies 

because they were not a substitute for the jurors’ “own 

independent assessment of the evidence.” While other 

regulatory agencies had also rejected IARC’s classification, 

the district court did not err in concluding that evidence of 

additional regulators’ post-IARC conclusions would have 

been cumulative. Admitting all foreign regulatory 

conclusions would have invited the jury to weigh competing 

regulatory findings rather than independently assess the 

scientific evidence.

Even if these evidentiary decisions were erroneous, any 

error was harmless because it was “more probable than not 

that the . . . admission of the evidence did not affect the 

jury’s verdict.” United States v. Ramirez-Robles, 386 F.3d 

1234, 1244 (9th Cir. 2004) (internal quotation marks and 

citations omitted). Considering the strong limiting 

instruction and the expert testimony linking glyphosate to 

cancer, the jury would likely have reached the same 

causation verdict even without evidence of IARC’s 

classification or with more evidence of regulatory agency 

rejections of that classification. Therefore, we affirm the 

decision to admit the conclusions from IARC, EPA, EFSA, 

and ECA, and to exclude evidence from additional 

regulatory agencies.

V

Monsanto also challenges the district court’s causation 

jury instruction. We review de novo whether that instruction 

correctly states the law. Peralta v. Dillard, 744 F.3d 1076, 

1082 (9th Cir. 2014) (en banc). We conclude that the district 
HARDEMAN V. MONSANTO 45

court’s causation jury instruction was inconsistent with the 

Judicial Council of California Civil Jury Instructions 

(“CACI”) and California case law. We conclude, however, 

that any error was harmless. See Caballero v. City of 

Concord, 956 F.2d 204, 206 (9th Cir. 1992).

The district court’s causation jury instruction included a 

substantial factor and but-for causation instruction, drawing 

from CACI 430, and a concurrent independent causes 

instruction.17 The first paragraph of this instruction (on 

substantial factor and but-for causation) adopted the same 

17 The jury was instructed as follows:

To prevail on the question of medical causation, 

Mr. Hardeman must prove by a preponderance of the 

evidence that Roundup was a substantial factor in 

causing his non-Hodgkin’s lymphoma. A substantial 

factor is a factor that a reasonable person would 

consider to have contributed to the harm. It must be 

more than a remote or trivial factor. It does not have 

to be the only cause of the harm. Subject to the 

additional instructions below, conduct is not a 

substantial factor in causing harm if the same harm 

would have occurred without that conduct.

The following additional instructions apply if you 

believe that two or more NHL-causing factors 

operated independently on Mr. Hardeman:

If you conclude that Mr. Hardeman has proven that his 

exposure to Roundup was sufficient on its own to 

cause his NHL, then you must find for Mr. Hardeman 

even if you believe that other factors were also 

sufficient on their own to cause his NHL. On the other 

hand, if you conclude that Mr. Hardeman has not 

proven that his exposure to Roundup was sufficient on 

its own to cause his NHL, then you must find for 

Monsanto.
46 HARDEMAN V. MONSANTO

language as CACI 430, the model “substantial factor” 

instruction. The district court’s instruction included 

CACI 430’s final optional sentence on but-for causation that 

reads, “[c]onduct is not a substantial factor in causing harm 

if the same harm would have occurred without that conduct.” 

But CACI 430’s “Directions for Use” instruct courts to “not 

include the [but-for instruction] in a case involving 

concurrent independent causes,” which the district court did 

here. As such, “the but-for test is inappropriate in cases 

when two forces are actively operating and each is sufficient 

to bring about the harm.” Lopez v. The Hillshire Brands Co., 

254 Cal. Rptr. 3d 377, 383–84 (Ct. App. 2019) (quoting 

Major v. R.J. Reynolds Tobacco Co., 222 Cal. Rptr. 3d 563, 

579 (Ct. App. 2017)). And this makes sense considering that 

the two instructions tend to contradict each other when used 

together.

Here, the district court’s causation jury instruction 

erroneously incorporated the optional final sentence of 

CACI 430. The concurrent independent causation 

instruction was appropriate—otherwise, the jury might not 

have found causation, even if it thought Roundup caused 

Hardeman’s cancer, because HCV may have been an 

additional cause. See Viner v. Sweet, 70 P.3d 1046, 1051 

(Cal. 2003) (explaining there is an exception to but-for cause 

for “multiple forces operating at the same time and 

independently, each of which would have been sufficient by 

itself to bring about the harm”). But because the concurrent 

independent causation instruction inherently conflicted with 

but-for causation, the district court’s jury instruction did not 

state the law entirely correctly. See Peralta, 744 F.3d 

at 1082. We recognize the district court tried to alleviate this 

conflict by adding the introductory language of “[s]ubject to 

the additional instructions below,” before providing the but-
HARDEMAN V. MONSANTO 47

for causation instruction, but we still find that language 

confusing, such that the instruction was “misleading.” Id.

An erroneous instruction does not require reversal, 

however, when “the error is more probably than not 

harmless.” Caballero, 956 F.2d at 206 (citation omitted). 

That standard is “less stringent than review for harmless 

error in a criminal case” and “more stringent than review for 

sufficiency of the evidence.” Id. at 207. Because the 

instruction given likely did not prejudice Monsanto, the 

harmlessness standard is met. For instance, if the jury did 

not view the but-for instruction as a bar to finding causation, 

then it applied the appropriate causation standard. And even 

if the jury interpreted the optional but-for sentence from 

CACI 430 to mean Hardeman could only prevail if Roundup 

was a but-for cause, then it would have also found legal 

causation under the more flexible concurrent independent 

causation standard. Thus, we affirm because the error in the 

causation instruction was likely harmless.

VI

Monsanto argues it was entitled to judgment as a matter 

of law on the failure-to-warn claims because it did not know 

and could not have known that glyphosate caused cancer in 

2012 (when Hardeman stopped using Roundup). But 

reviewing de novo and “view[ing] the evidence in the light 

most favorable to [Hardeman] . . . and draw[ing] all 

reasonable inferences in h[is] favor,” Lakeside-Scott v. 

Multnomah Cnty., 556 F.3d 797, 802 (9th Cir. 2009), we 

conclude that sufficient scientific evidence was presented to 

the jury to support that the association between glyphosate 

and cancer was “knowable” by 2012.

To prevail on his failure-to-warn claim, Hardeman was 

required to prove that the link between Roundup and cancer 
48 HARDEMAN V. MONSANTO

was “known or knowable in light of the generally recognized 

and prevailing best scientific and medical knowledge 

available at the time of manufacture and distribution.” 

Anderson v. Owens–Corning Fiberglas Corp., 810 P.2d 549, 

558 (Cal. 1991). While the “scientific landscape” was “more 

favorable” to Monsanto before 2012, there was sufficient 

scientific evidence presented to the jury that the link between 

glyphosate and cancer was “knowable.”

For instance, as early as 1985, EPA classified glyphosate 

as a possible human carcinogen after reviewing a mouse 

study finding that “[g]lyphosate was oncogenic in male 

mice,” causing rare tumors. Even though EPA changed its 

designation of glyphosate to non-carcinogenic in 1991, 

several studies found an association between glyphosate and 

cancer in the 1990s. In the late 1990s, Monsanto hired 

Dr. Parry, a genotoxicologist, who found evidence that 

glyphosate may be genotoxic and urged Monsanto to 

conduct specific tests on Roundup’s genotoxicity. Though 

Monsanto never conducted all the tests Dr. Parry 

requested,18 various independent scientific studies linking 

glyphosate and cancer were released by 2012. Thus, 

sufficient evidence was presented to the jury that the 

association between glyphosate and cancer was, at 

minimum, “knowable” by 2012, and Monsanto was 

therefore not entitled to judgment as a matter of law.

VII

Finally, we address both parties’ challenges to the 

punitive damages award. We review whether California law 

18 Years later, in 2009, Monsanto toxicologist Donna Farmer said, 

“you cannot say that Roundup does not cause cancer . . . [because] we 

have not done carcinogenicity studies with ‘Roundup.’”
HARDEMAN V. MONSANTO 49

permits a jury’s decision to award punitive damages for 

substantial evidence. Kaffaga v. Estate of Steinbeck, 

938 F.3d 1006, 1013 (9th Cir. 2019). We review de novo, 

with an “[e]xacting appellate review,” the constitutionality 

of a punitive damages award. State Farm Mut. Auto. Ins. 

Co. v. Campbell, 538 U.S. 408, 418 (2003) (citing Cooper 

Indus., Inc. v. Leatherman Tool Grp., Inc., 532 U.S. 424, 436 

(2001)). “[W]e defer to the district court’s ‘findings of fact 

unless they are clearly erroneous.’” Arizona v. ASARCO 

LLC, 773 F.3d 1050, 1054 (9th Cir. 2014) (quoting Cooper 

Indus., 532 U.S. at 440 n.14). Based on this review, we hold 

that (1) California law permits a punitive damages award 

because substantial evidence was presented to the jury that 

Monsanto acted with malice, and (2) though the $75 million 

punitive damages award was constitutionally excessive, the 

reduced $20 million award comports with the outer limits of 

the Due Process Clause.

A

Punitive damages were permissible under California law 

because substantial evidence was presented that Monsanto 

acted with malice by, among other things, ignoring 

Roundup’s carcinogenic risks. See Kaffaga, 938 F.3d 

at 1018.

Punitive damages are permissible under California law 

when there is “clear and convincing evidence that the 

defendant has been guilty of oppression, fraud, or malice.” 

Cal. Civ. Code § 3294(a). As relevant here, “malice” means 

“despicable conduct which is carried on by the defendant 

with a willful and conscious disregard of the rights or safety 

of others.” § 3294(c)(1).

That definition of malice requires that we examine what 

constitutes “despicable conduct” and “conscious disregard.” 
50 HARDEMAN V. MONSANTO

“Despicable conduct” is conduct “so vile, base, 

contemptible, miserable, wretched or loathsome that it 

would be looked down upon and despised by most ordinary 

decent people.” Pac. Gas & Elec. Co. v. Super. Ct., 235 Cal. 

Rptr. 3d 228, 236 (Ct. App. 2018) (internal quotation marks 

and citation omitted). “Conscious disregard” requires that 

the defendant “have actual knowledge of the risk of harm it 

is creating and, in the face of that knowledge, fail to take 

steps it knows will reduce or eliminate the risk of harm.” Id. 

(internal quotation marks and citation omitted). But whether 

a “defendant is aware of the probable dangerous 

consequences of [its] conduct and [it] willfully fails to avoid 

such consequences” can be “proved either expressly through 

direct evidence or by implication through indirect evidence 

from which the jury draws inferences.” Pfeifer v. John 

Crane, Inc., 164 Cal. Rptr. 3d 112, 135 (Ct. App. 2013) 

(quoting Angie M. v. Super. Ct., 44 Cal. Rptr. 2d 197, 204 

(Ct. App. 1995)).

Substantial evidence of Monsanto’s malice was 

presented to the jury, supporting punitive damages under 

§ 3294(a). For example, internal emails were presented 

supporting that Monsanto was consciously aware of the 

potential health risks associated with Roundup. One email, 

from Monsanto toxicologist Mark Martens, read, “I don’t 

know for sure how suppliers would react—but if somebody 

came to me and said they wanted to test Roundup I know 

how I would react—with serious concern.” A second email, 

from Monsanto toxicologist William Heydens, read, 

“[g]lyphosate is OK but the formulated product (and thus the 

surfactant) does the damage.” And a third email, from 

Monsanto toxicologist Donna Farmer, read, “you cannot say 

that Roundup is not a carcinogen . . . [because] we have not 

done the necessary testing on the formulation to make that 

statement.” These emails provide the substantial evidence 
HARDEMAN V. MONSANTO 51

necessary to support punitive damages based on Monsanto’s 

awareness that Roundup posed a potential health risk.

There was also substantial evidence sufficient for a jury 

to find that Monsanto “fail[ed] to take steps it kn[ew] 

w[ould] reduce or eliminate the risk of harm.” Pac. Gas & 

Elec. Co., 235 Cal. Rptr. 3d at 236 (internal quotation marks 

and citation omitted). For instance, after its own hired 

expert, Dr. Parry, found that glyphosate—alone and when 

mixed with other chemicals in Roundup—had increased 

genotoxic risks, evidence was sufficient to infer that 

Monsanto largely failed to perform further studies. Instead, 

Monsanto helped author an article downplaying 

glyphosate’s health and safety concerns. Even though “it is 

also possible to draw a contrary conclusion” that Monsanto 

was ignorant or negligent (but not malicious),19 the “jury’s 

verdict must be upheld [because] it is supported by

substantial evidence” that Monsanto consciously 

disregarded Roundup’s potential harm. See Pavao v. Pagay, 

307 F.3d 915, 918 (9th Cir. 2002).

B

We next turn to the amount of punitive damages that 

would still comport with the Due Process Clause. Hardeman 

argues that the district court erred by reducing the jury’s 

$75 million punitive damages award to $20 million. And 

Monsanto contends that even the reduced punitive damages 

award was unconstitutional under the Due Process Clause. 

19 Monsanto also argues that it cannot be deemed to have acted with 

malice because it complied with regulations. But “[a] defendant’s 

compliance with, or actions consistent with, governmental regulations or 

determinations about a product do not necessarily eviscerate a claim for 

punitive damages.” Johnson & Johnson Talcum Powder Cases, 249 Cal. 

Rptr. 3d 642, 678 (Ct. App. 2019).
52 HARDEMAN V. MONSANTO

Consistent with our “[e]xacting appellate review,” State 

Farm, 538 U.S. at 418 (citing Cooper Indus., 532 U.S. 

at 436), we lay out some fundamental principles underlying 

the constitutionality of punitive damages awards.

“Compensatory damages and punitive damages serve 

different purposes; compensatory damages redress concrete 

loss caused by the defendant’s wrongful conduct, while 

punitive damages are aimed at deterrence and retribution.” 

Planned Parenthood of Columbia/Willamette Inc. v. Am. 

Coal. of Life Activists, 422 F.3d 949, 953 (9th Cir. 2005) 

(citing State Farm, 538 U.S. at 416; Cooper Indus., 532 U.S. 

at 432). Further, “[t]he Supreme Court has instructed us to 

go ‘no further’ if a ‘more modest punishment’ for the 

‘reprehensible conduct’ at issue ‘could have satisfied the 

State’s legitimate objectives’ of punishing and deterring 

future misconduct.” Lompe v. Sunridge Partners, LLC, 

818 F.3d 1041, 1065 (10th Cir. 2016) (quoting State Farm, 

538 U.S. at 419–20). Ultimately, we are mindful that in 

applying the Due Process Clause, it is “a constitution we are 

expounding.” Tabares v. City of Huntington Beach, 

988 F.3d 1119, 1122 (9th Cir. 2021) (quoting McCulloch v. 

Maryland, 17 U.S. 316, 407 (1819)).

When punitive damages are “grossly excessive,” they 

violate the Due Process Clause. State Farm, 538 U.S. at 416. 

Whether punitive damages are “grossly excessive” depends 

on three factors: “(1) the degree of reprehensibility of the 

defendant’s misconduct; (2) the disparity between the actual 

or potential harm suffered by the plaintiff and the punitive 

damages award; and (3) the difference between the punitive 

damages awarded by the jury and the civil penalties 

authorized or imposed in comparable cases.” Id. at 418 

(citing BMW of N. Am., Inc. v. Gore, 517 U.S. 559, 575 

(1996)).
HARDEMAN V. MONSANTO 53

1

The weightiest factor is “the degree of reprehensibility 

of the defendant’s conduct.” Gore, 517 U.S. at 575. The 

district court found “Monsanto’s approach to the safety of its 

product was indeed reprehensible.” In re Roundup Prods. 

Liab. Litig., 385 F. Supp. 3d 1042, 1047 (N.D. Cal. 2019). 

The district court’s finding was reasonable and supported by 

the facts presented to the jury. Thus, the question is to what 

degree Monsanto’s actions were reprehensible. We 

determine the reprehensibility of Monsanto’s conduct by 

considering the following five factors: whether “[1] the harm 

caused was physical as opposed to economic; [2] the tortious 

conduct evinced an indifference to or a reckless disregard of 

the health or safety of others; [3] the target of the conduct 

had financial vulnerability; [4] the conduct involved 

repeated actions or was an isolated incident; and [5] the harm 

was the result of intentional malice, trickery, or deceit, or 

mere accident.” State Farm, 538 U.S. at 419 (citing Gore, 

517 U.S. at 576–77).

Several aggravating factors associated with 

reprehensible conduct are present based on the evidence at 

trial. First, the harm inflicted on Hardeman—cancer—was 

physical, not purely economic. Hardeman has already been 

well compensated for damages resulting from his physical 

injury. Indeed, $5,066,667 of the compensatory damages—

about 96% of the jury’s $5,267,634.10 total compensatory 

award—was based on noneconomic harm. See In re 

Roundup, 385 F. Supp. 3d at 1045. The district court found 

the $2 million in compensatory damages related to future 

noneconomic harm were “borderline” high because 

Hardeman’s cancer was in remission. Id. And while 

remission is “no guarantee,” testimony showed his cancer is 

unlikely to return. Id. But, as the district court explained, 
54 HARDEMAN V. MONSANTO

this concern was “mitigate[d]” because “the jury likely 

intended the future award to compensate a longer period of 

suffering.” Id. These factual findings by the district court, 

which are reasonable and not clearly erroneous, highlight the 

reprehensibility of causing serious physical harm and the 

need to deter future harm. While Hardeman was well 

compensated for past and future harm, the serious nature of 

the harm supports finding that Monsanto’s actions were 

reprehensible.

Second, the district court’s factual conclusion that 

Monsanto ignored safety risks is not clearly erroneous and 

also supports reprehensibility. For example, the district 

court found that “Monsanto’s behavior betrayed a lack of 

concern about the risk that its product might be 

carcinogenic.” Id. at 1047. In addition, it found that “the 

evidence at trial painted the picture of a company focused on 

attacking or undermining the people who raised concerns, to 

the exclusion of being an objective arbiter of Roundup’s 

safety.” Id. But the district court also found mitigating 

evidence. Notwithstanding the jury’s verdict for Hardeman, 

the district court explained that “the metaphorical jury is still 

out on whether glyphosate causes NHL.” Id. Indeed, “there 

is credible evidence on both sides of the scientific debate” 

which “surely diminish[es]—to a degree—Monsanto’s 

culpability.” Id. Moreover, “[t]he scientific landscape was 

even more favorable to Monsanto during the time 

Mr. Hardeman was using Roundup.” Id.

We also agree with the district court that no evidence was 

presented that Monsanto knew Roundup in fact caused 

cancer. Monsanto never conducted studies that may have 

indicated (as its scientists suspected) that Roundup was 

carcinogenic. And regulators, like EPA, have repeatedly 

found glyphosate to not have carcinogenic risks. But, as the 
HARDEMAN V. MONSANTO 55

district court found, the evidence supports that Monsanto 

knew Roundup might cause cancer, hence its concern and 

reluctance to, for instance, conduct Dr. Parry’s 

recommended studies. We have no quibble with any of the 

district court’s findings of fact. Ultimately, evidence of 

Monsanto’s conduct—downplaying concerns and failing to 

fully assess Roundup’s safety after being alerted to possible 

risks—supports that Monsanto acted with “indifference to or 

a reckless disregard of the health or safety of others.” State 

Farm, 538 U.S. at 419.

Third, State Farm asks us to look at Hardeman’s 

financial vulnerability. Id. It goes without saying that this 

is a case of a large corporation and an individual—not two 

corporations on equal footing. Having said that, this factor 

is not particularly relevant in a mostly noneconomic 

damages case like this one. See Lompe, 818 F.3d at 1066 

(“But as a practical matter, the financial vulnerability factor 

does not have particular relevance . . . where the harm 

[plaintiff] suffered was physical rather than a reprehensible 

exploitation of financial vulnerability through fraud or other 

financial misconduct.”). The district court below did not 

analyze this factor. We do not find this factor helpful one 

way or another to establish reprehensibility.

Fourth, the district court did not clearly err in finding that 

Monsanto’s “conduct involved repeated actions” instead of 

“an isolated incident.” See In re Roundup, 385 F. Supp. 3d 

at 1047 (quoting State Farm, 538 U.S. at 419). Evidence 

was presented that Monsanto repeatedly sold Roundup 

without a warning label. Id. Thus, this factor supports 

reprehensibility because “repeated misconduct is more 

reprehensible than an individual instance of malfeasance.” 

Gore, 517 U.S. at 577.
56 HARDEMAN V. MONSANTO

Fifth, the district court recognized Monsanto’s actions 

exhibited malice but also made findings of fact that 

mitigated this factor. The district court noted there was no 

evidence “that Monsanto hid evidence from the EPA or, 

alternatively, that it had managed to capture the EPA.” See 

In re Roundup, 385 F. Supp. 3d at 1047. There was also no 

evidence “that Monsanto was in fact aware that glyphosate 

caused cancer but concealed it, thus distinguishing this case 

from the many cases adjudicating the conduct of the tobacco 

companies.” Id. Nonetheless, there was evidence of 

Monsanto’s malice. As the district court found, “[d]espite 

years of colorable claims in the scientific community that 

Roundup causes NHL,” emails showed “Monsanto 

employees crassly attempting to combat, undermine or 

explain away challenges to Roundup’s safety.” Id. And “not 

once was [the jury] shown an email suggesting that 

Monsanto officials were actively committed to conducting 

an objective assessment of its product.” Id. We do not find 

the district court’s findings of fact clearly erroneous.

Based upon the district court’s findings, four of the five 

factors support that Monsanto’s actions were reprehensible. 

But in two of those factors, there were significant mitigating 

considerations which suggest that Monsanto’s actions, while 

reprehensible, were not “particularly egregious.” See Gore, 

517 U.S. at 582.

2

We next examine the disparity between harm to 

Hardeman and the punitive damages award by looking to the 

Supreme Court’s guidelines on appropriate ratios. State 

Farm, 538 U.S. at 424. The Supreme Court has explained 

that “[s]ingle-digit multipliers are more likely to comport 

with due process, while still achieving the State’s goals of 

deterrence and retribution.” Id. at 425. “[A]n award of more 
HARDEMAN V. MONSANTO 57

than four times the amount of compensatory damages might 

be close to the line of constitutional impropriety.” Id. (citing 

Pac. Mut. Life Ins. Co. v. Haslip, 499 U.S. 1, 23–24 (1991)). 

But there are “no rigid benchmarks that a punitive damages 

award may not surpass” and greater ratios might “comport 

with due process where ‘a particularly egregious act has 

resulted in only a small amount of economic damages.’” Id.

(quoting Gore, 517 U.S. at 582).

Here, the jury awarded $5,267,634.10 in compensatory 

damages and $75 million (approximately 14.2 times the 

compensatory amount) in punitive damages. But 

Monsanto’s conduct—though plausibly viewed as 

reprehensible—was not “particularly egregious” as to 

warrant a damages ratio above the single-digit range, 

especially considering the absence of evidence showing a 

known safety risk was intentionally concealed. See id. Thus, 

we have little trouble holding that the jury’s 14.2 to 1 ratio 

violated due process.

The $5,267,634.10 compensatory damages award was 

substantial. See, e.g., Ramirez v. TransUnion LLC, 951 F.3d 

1008, 1037 (9th Cir. 2020), cert. granted in part on other 

grounds, No. 20-297, 2020 WL 7366280 (U.S. Dec. 16, 

2020) (describing $8 million compensatory damages award 

as “quite substantial”); Lompe, 818 F.3d at 1069 

(“[C]ompensatory damages have often been considered 

‘substantial’ when they are over $1,000,000.”). “When 

compensatory damages are substantial, then a lesser ratio, 

perhaps only equal to compensatory damages, can reach the 

outermost limit of the due process guarantee.” State Farm, 

538 U.S. at 425. But “State Farm’s 1:1 compensatory to 

punitive damages ratio is not binding, no matter how 

factually similar the cases may be.” Hangarter v. Provident 

Life & Accident Ins. Co., 373 F.3d 998, 1014 (9th Cir. 2004). 
58 HARDEMAN V. MONSANTO

Considering these precedents, we have held that “[i]n cases 

where there are significant economic damages and punitive 

damages are warranted but behavior is not particularly 

egregious, a ratio of up to 4 to 1 serves as a good proxy for 

the limits of constitutionality.” Planned Parenthood, 

422 F.3d at 962.

Even though “substantial” compensatory damages were 

awarded here, the evidence justifies a damages ratio higher 

than 1 to 1. Monsanto intentionally downplayed and ignored 

calls to test Roundup’s carcinogenic risks, and the jury 

determined that Roundup caused Hardeman’s cancer. 

Coupled with the physical damage—cancer—these factors 

suggest a damages ratio up to 4 to 1 “serves as a good proxy 

for the limits of constitutionality.” Id.; see State Farm, 

538 U.S. at 425 (“The precise award in any case, of course, 

must be based upon the facts and circumstances of the 

defendant’s conduct and the harm to the plaintiff.”).

3

Third, the district court speculated that fines for failure 

to warn of a product’s risk under FIFRA and the California 

Health and Safety Code could potentially “over time[] 

become quite high” because “both state and federal law 

calculate penalties per violation.” In re Roundup, 385 F. 

Supp. 3d at 1048; see also 7 U.S.C. § 136j(a)(1)(E); 

40 C.F.R. § 19.4; Cal. Health & Safety Code § 25249.7. We 

note the need to avoid speculation in analyzing this factor. 

See State Farm, 538 U.S. at 428 (rejecting consideration of 

speculative future penalties unrelated to plaintiffs’ harm). 

The parties failed below, and again on appeal, to explain 

what the relevant civil fines are, how they would be 

calculated, and even whether they would be warranted. See 

In re Roundup, 385 F. Supp. 3d at 1048. Monsanto points 

out, however, that no civil or criminal fines have been 
HARDEMAN V. MONSANTO 59

imposed, apparently by any federal or any state agency, 

including California.

Though California in 2017 categorized glyphosate as a 

chemical known to the state to cause cancer, see Glyphosate 

Proposition 65, it is also not clear that Monsanto would have 

been subject to civil fines under California law in 2012. 

Because neither party presents argument or evidence, we 

agree with the district court that this guidepost is not 

“particularly helpful here.” See id. at 1048 (“[A]bsent an 

explanation from either party about how these penalties 

would be calculated, it is difficult to use them as a 

benchmark.”).

* * *

We hold that the jury’s $75 million punitive damages 

award was “grossly excessive” given the mitigating factors 

found by the district court. See State Farm, 538 U.S. at 416. 

Considering the evidence of reprehensibility, however, we 

hold that the district court’s reduced $20 million punitive 

damages award (a 3.8 to 1 damages ratio), while at the outer 

limits of constitutional propriety, ultimately comports with 

due process. Planned Parenthood, 422 F.3d at 962; see also 

Ramirez, 951 F.3d at 1037 (upholding 4 to 1 ratio where 

$8 million compensatory damages awarded).

Though we uphold the district court’s $20 million 

punitive damages award, we emphasize that the award is 

“close to the line of constitutional impropriety.” See State 

Farm, 538 U.S. at 425. Considering the number of cases 

pending in this Roundup multidistrict litigation, we 

recognize a smaller punitive damages award in other cases 

may safely satisfy due process concerns by still imposing the 

appropriate punishment and achieving the goals of 

deterrence and retribution. Cf. Lompe, 818 F.3d at 1065 
60 HARDEMAN V. MONSANTO

(“The Supreme Court has instructed us to go ‘no further’ if 

a ‘more modest punishment’ for the ‘reprehensible conduct’ 

at issue ‘could have satisfied the State’s legitimate 

objectives’ of punishing and deterring future misconduct.” 

(quoting State Farm, 538 U.S. at 419–20)); see, e.g.,

Johnson v. Monsanto Co., 266 Cal. Rptr. 3d 111, 129 (Ct. 

App. 2020), as modified on denial of reh’g (Aug. 18, 2020), 

review denied (Oct. 21, 2020) (reducing punitive damages 

award in a Roundup case to a 1 to 1 ratio with compensatory 

damages of $10.3 million and where facts of Monsanto’s 

reprehensibility were likely stronger than this case).

VIII

We are aware this appeal involves a bellwether trial with 

potentially thousands of federal cases to follow. But many 

of our holdings are fact-specific. Different Roundup cases 

may present different considerations, leading to different 

results. For example, were there evidence that EPA took 

certain enforcement action against Monsanto after a cancer 

warning was added to Roundup’s label, perhaps the 

preemption analysis would lead to a different outcome. And 

while our holding that expert testimony was admissible here 

may be applicable to other Roundup cases, much of this 

expert testimony was unique to Hardeman’s specific case. 

Thus, it would not be unreasonable for the district court to 

revisit the admissibility of expert testimony based upon the 

facts raised in future cases. Similarly, despite the punitive 

damages upheld here, a smaller punitive damages award in 

future cases may better comport with due process. 

Ultimately, we agree that the district court in this case either 

reached the correct result or need not be reversed.

AFFIRMED.
HARDEMAN V. MONSANTO 61

N.R. SMITH, Circuit Judge, dissenting to section VII.B.

After a mandated de novo review of the district court’s 

punitive damages award, determining if the amount was 

constitutionally excessive (not simply determining whether 

the award was acceptable or reasonable), I must dissent. Let 

me explain.

Punitive damages are “‘quasi-criminal,’ operat[ing] as 

‘private fines’ intended to punish the defendant and to deter 

future wrongdoing.” Cooper Indus., Inc. v. Leatherman 

Tool Grp., Inc., 532 U.S. 424, 432 (2001) (quoting Pacific 

Mut. Life Ins. Co. v. Haslip, 499 U.S. 1, 19 (1991)). 

“Exacting appellate review ensures that an award of punitive 

damages is based upon an ‘application of law, rather than a 

decisionmaker’s caprice.’” State Farm Mut. Auto. Ins. Co. 

v. Campbell, 538 U.S. 408, 418 (2003). As the majority has

stated, “the Supreme Court has instructed us to go ‘no 

further’ if a ‘more modest punishment’ for the ‘reprehensible 

conduct’ at issue ‘could have satisfied the State’s legitimate 

objectives’ of punishing and deterring future misconduct.” 

Lompe v. Sunridge Partners, LLC, 818 F.3d 1041, 1065 

(10th Cir. 2016) (quoting State Farm, 538 U.S. at 419–20). 

In order to determine de novo whether the punishment is 

“grossly excessive,” the Supreme Court requires us “to 

consider three guideposts: (1) the degree of reprehensibility 

of the defendant’s misconduct; (2) the disparity between the 

actual or potential harm suffered by the plaintiff and the 

punitive damages award; and (3) the difference between the 

punitive damages awarded by the jury and the civil penalties 

authorized or imposed in comparable cases.” State Farm, 

538 U.S. at 417–18. Of course, we always defer to the 

district court’s findings of fact unless they are clearly 

erroneous. Cooper Indus., 532 U.S. at 440 n.14.
62 HARDEMAN V. MONSANTO

The district court made the following findings of fact, 

upon which one must make the analysis:

a. The jury found it was more likely than not 

that Roundup (the glyphosate therein) 

was a “substantial factor” in causing 

Hardeman’s NHL. In order to evidence 

that Roundup was a substantial factor in 

this cause, Hardeman’s experts only 

performed a differential diagnosis. 

Differential diagnosis is a methodology 

by which a physician “rules in” all 

potential causes of a disease, “rules out” 

those for “which there is no plausible 

evidence of causation, and then 

determines the most likely cause among 

those that cannot be excluded.”

b. NHL is a cancer that affects white blood 

cells in the immune system. 

Approximately 70% or more of the NHL 

cases are idiopathic, meaning they 

develop for unknown reasons. However, 

some causes of NHL, such as hepatitis C 

(HCV), are well established. Hardeman 

had HCV for 25 to 40 years before 

developing NHL.

c. Hardeman was diagnosed with NHL in 

early 2015. He started using Roundup in 

the 1980s but ended his use in 2012. 

During the time Hardeman was using 

Roundup, the scientific landscape (of 

whether it could cause cancer) was more 

favorable to Monsanto than at the time of 

trial. In 2012, EPA had little to no 
HARDEMAN V. MONSANTO 63

evidence that glyphosate was at all 

carcinogenic in humans. Not until 2015 

did the International Agency for Research 

on Cancer (“IARC”) suggest that 

glyphosate was probably carcinogenic to 

humans.

d. Even today, there is credible evidence on 

both sides with regard to whether 

glyphosate causes NHL as documented 

by the repeated approvals of glyphosate 

by EPA, the European Chemicals 

Agency, Health Canada, and other 

worldwide regulatory agencies.

e. There is no evidence that Monsanto was 

in fact aware that glyphosate caused 

cancer; that Monsanto concealed it from 

EPA; or that Monsanto somehow had 

“captured” those in EPA, such that EPA 

would not take a position contrary to 

Monsanto.

f. The record at best shows that Monsanto 

knew Roundup might cause cancer but 

made minimal efforts to determine 

whether the scientific evidence (finding 

glyphosate may cause NHL) was 

accurate.

g. However, Monsanto did attack or 

undermine those who raised concerns for 

Roundup’s safety.
64 HARDEMAN V. MONSANTO

h. Monsanto has sold Roundup without a 

warning label.1

i. The award of future noneconomic 

damages was not based on physical pain 

or impairment but was limited to 

“anxiety, mental suffering, loss of 

enjoyment of life, emotional distress, and 

inconvenience.”

j. Hardeman’s NHL is now in remission, 

his prognosis is “very good” and it is 

“extremely unlikely” that his NHL will 

return.

See In re Roundup Prod. Liab. Litig., 385 F. Supp. 3d 1042, 

1047 (N.D. Cal. 2019).

1. The degree of reprehensibility of Monsanto’s 

conduct.

Considering each of the three guideposts, the degree of 

reprehensibility is “[t]he most important indicium of the 

reasonableness of a punitive damages award.” See State 

Farm, 538 U.S. at 419. The degree of reprehensibility is 

determined by considering (1) “the harm caused was 

physical as opposed to economic”; (2) “the tortious conduct 

evinced an indifference to or a reckless disregard of the 

health or safety of others”; (3) the target of the conduct had 

financial vulnerability”; (4) “the conduct involved repeated 

actions or was an isolated incident”; and (5) “the harm was 

1 The district court noted that Monsanto continues to sell Roundup 

without a warning label. However, “the conduct that harmed [plaintiff] 

is the only conduct relevant to the reprehensibility analysis.” State Farm, 

538 U.S. at 424.
HARDEMAN V. MONSANTO 65

the result of intentional malice, trickery, or deceit, or mere 

accident.” Id. Applying the facts (as determined by the 

district court) de novo to these five considerations, 

Monsanto’s conduct from the 1980s to 2012 did not 

constitute the degree of “reprehensible conduct” that would 

warrant an award of punitive damages at a 3.8:1 ratio. See 

id. Reviewing these five considerations instead 

demonstrates a low degree of reprehensibility.

First, while Hardeman suffered from physical harm 

(NHL), he was well compensated for it by the jury. 

Importantly, the physical harm suffered was not based on 

acts or threats of violence, see Florez v. Delbovo, 939 F. 

Supp. 1341, 1348 (N.D. Ill. 1996) (explaining that “acts of 

violence or threats of bodily harm” are “the most 

reprehensible” (citing BMW of N. Am., Inc. v. Gore, 517 U.S. 

559, 575 (1996)), or “from some physical assault or trauma,” 

see State Farm, 538 U.S. at 426. Further, (as demonstrated 

below) Monsanto did not engage in deliberate conduct to 

exploit Hardeman and expose him to a risk of cancer. Cf. 

Bullock v. Philip Morris USA, Inc., 131 Cal. Rptr. 3d 382, 

396 (Ct. App. 2011) (concluding “that in a case involving 

physical harm, the physical or physiological vulnerability of 

the target of the defendant’s conduct is an appropriate factor 

to consider in determining the degree of reprehensibility, 

particularly if the defendant deliberately exploited that 

vulnerability”).

Second, one must determine whether Monsanto’s 

conduct evinced “indifference to or a reckless disregard of

the health or safety of others.” State Farm, 538 U.S. at 419. 

In California, Hardeman had to demonstrate that Monsanto 

“had been guilty of oppression, fraud, or malice,” in order to 

be awarded punitive damages from Monsanto. Cal. Civ. 

Code § 3294(a). Section 3294(c)(1) outlines that 
66 HARDEMAN V. MONSANTO

Monsanto’s conduct must have been undertaken “with a 

willful and conscious disregard of the rights or safety of 

others.” A conscious disregard “requires that the defendant 

have actual knowledge of the risk of harm it is creating and, 

in the face of that knowledge, fail[ed] to take steps it kn[ew 

would] reduce or eliminate the risk of harm.” Ehrhardt v. 

Brunswick, Inc., 231 Cal. Rptr. 60, 65 (Ct. App. 1986). 

Given this standard, although ignoring evidence that 

Roundup might cause cancer could be substantial evidence 

to establish punitive damages against Monsanto, there was 

and still exists “credible evidence on both sides of the 

debate” about whether Roundup actually does cause cancer. 

During the time that Hardeman used Roundup, the evidence 

was scant that Roundup may cause cancer, but Monsanto did 

disregard it. However, its conduct does not demonstrate (nor 

did the court find) that Monsanto intentionally targeted 

Hardeman.

Third, there is no evidence in the record that the target of 

the conduct (Hardeman) had financial vulnerability. See 

Clark v. Chrysler Corp., 436 F.3d 594, 604 (6th Cir. 2006) 

(“The financial vulnerability of a target is particularly 

relevant when the harm inflicted is economic in nature.”). 

The wealth of Monsanto cannot justify an award of punitive 

damages absent a connection of its “financial resources and 

the physical injury suffered” by Hardeman. See id.

Fourth, Monsanto’s failure to place a warning on 

Roundup’s label does not constitute “repeated actions.”2 See 

Gore, 517 U.S. at 577. “[E]vidence that a defendant has 

repeatedly engaged in prohibited conduct while knowing or 

suspecting that it was unlawful would provide relevant 

2 As previously noted, the district court seems to rely on conduct 

that occurred post 2012 in determining the reprehensibility.
HARDEMAN V. MONSANTO 67

support for an argument that strong medicine is required to 

cure the defendant’s disrespect for the law.” Id. at 576–77. 

At the time Hardeman used the product, Monsanto was not 

engaging in unlawful conduct. At that time, EPA had little 

to no evidence that glyphosate was carcinogenic in humans. 

In fact (again), there is credible evidence (to this day) on 

both sides with regard to whether glyphosate causes NHL. 

Notably, IARC did not decide to classify glyphosate as 

“probably carcinogenic to humans” until 2015 (three years 

after Hardeman stopped using Roundup). See In re Roundup 

Prod. Liab. Litig., 385 F. Supp. 3d at 1047. Further, after 

California’s passage of Proposition 65 (requiring a warning 

label for glyphosate), Michael L. Goodis, EPA, Office of 

Pesticide Programs, sent a letter to registrants (like 

Monsanto) challenging Proposition 65 as contrary to “EPA’s 

determination that glyphosate is ‘not likely to be 

carcinogenic to humans.’” Proposed Interim Registration 

Review at 11. The letter charged that the Proposition 65 

warning was a “false and misleading statement” and violated 

the Federal Insecticide, Fungicide, and Rodenticide Act 

(“FIFRA”).

Fifth, Monsanto did not act with “intentional malice, 

trickery, or deceit.” See State Farm, 538 U.S. at 419. As the 

district court found, Monsanto acted with indifference, but 

Monsanto did not engage in intentional acts, trickery, or 

deceit.3

 See Williams v. First Advantage LNS Screening 

3 Even the majority does not conclude that Monsanto acted with 

“intentional malice, trickery, or deceit.” See Maj. Op. 53. Rather, it 

describes Monsanto’s conduct as “malice.” Id. at 56. However, 

“malice,” as found by the district court, means a “conscious disregard of 

the rights or safety of others.” See In re Roundup Prod. Liab. Litig., 

385 F. Supp. 3d at 1046 (quoting Cal. Civ. Code § 3294(c)(1)). Thus, 

there is no evidence that the harm suffered by Hardeman was the “result 

of intentional malice”; Monsanto did not “intend[] to cause injury” to 
68 HARDEMAN V. MONSANTO

Sols. Inc, 947 F.3d 735, 754 (11th Cir. 2020) (concluding 

that “[a]t worst, Defendant acted recklessly, but without any 

intent to harm Plaintiff”). In fact, Monsanto’s actions were 

not contrary to “government regulations.” See Johnson & 

Johnson Talcum Powder Cases, 249 Cal. Rptr. 3d 642, 678 

(Ct. App. 2019), review denied (Oct. 23, 2019). Although 

compliance with regulations cannot “eviscerate a claim for 

punitive damages,” id., it does evidence that the harm “was 

[not] the result of intentional malice, trickery, or deceit,” 

State Farm, 538 U.S. at 419. As the district court found, the 

association between Roundup and NHL “remains under 

scientific investigation” and there was no evidence of 

intentional acts on the part of Monsanto. Id.; cf. Satcher v. 

Honda Motor Co., 52 F.3d 1311, 1316–17 (5th Cir. 1995) 

(precluding punitive damages when there was a genuine 

dispute in the scientific community).

Lastly, in reviewing these considerations, “some wrongs 

are more blameworthy than others,” such as “violence,” 

“trickery and deceit,” or “intentional malice” and are more 

deserving of a higher punitive damages ratio. See Gore, 

517 U.S. at 575. We have suggested that this “hierarchy of 

reprehensibility” starts “with acts and threats of violence

. . . , followed by acts taken in reckless disregard for others’ 

health and safety, affirmative acts of trickery and deceit, and 

finally, acts of omission and mere negligence.” Swinton v. 

Potomac Corp., 270 F.3d 794, 818 (9th Cir. 2001) (citation 

Hardeman. See Gober v. Ralphs Grocery Co., 40 Cal. Rptr. 3d 92, 106 

(Ct. App. 2006). Nevertheless, despite a lack of evidence of this 

“important criterion,” the majority still concludes that a punitive 

damages award at outer constitutional boundaries for this case of 

significant compensatory damages was appropriate. See Rhone-Poulenc 

Agro, S.A. v. DeKalb Genetics Corp., 345 F.3d 1366, 1371 (Fed. Cir. 

2003) (noting that this “factor has become an important criterion of what 

the Constitution accepts as reprehensible conduct”).
HARDEMAN V. MONSANTO 69

and quotation marks omitted). Thus, “[i]n order to justify a 

substantial punitive damage award, a plaintiff ordinarily 

must prove that the defendants’ conduct falls at the upper 

end of the blameworthiness continuum, or, put another way, 

that the conduct reflects a high level of culpability.” 

Zimmerman v. Direct Fed. Credit Union, 262 F.3d 70, 82 

(1st Cir. 2001).

No review of these considerations reflects “a high level 

of culpability.” Id. Thus, Monsanto’s low degree of 

reprehensibility cannot constitutionally justify the district 

court’s substantial punitive damages award.

2. The disparity between harm suffered and 

punitive damages award.

“The second and perhaps most commonly cited indicium 

of an unreasonable or excessive punitive damages award is 

its ratio to the actual harm inflicted on the plaintiff.” Gore, 

517 U.S. at 580. In determining punitive damages for each 

case, the Supreme Court has outlined that “the precise 

award” of such damages “must be based upon the facts and 

circumstances of the defendant’s conduct and the harm to the 

plaintiff.” State Farm, 538 U.S. at 425. Although the Court 

has not drawn a “bright-line ratio” for punitive damages, the 

Court’s jurisprudence suggests “that, in practice, few awards 

exceeding a single digit-ratio between punitive and 

compensatory damages, to a significant degree, will satisfy 

due process.” Id. “A higher ratio may . . . be justified in 

cases” where (1) “the injury is hard to detect,” (2) “the 

monetary value of noneconomic harm might have been 

difficult to determine,” or (3) “a particularly egregious act 

has resulted in only a small amount of [compensatory] 

damages.” Gore, 517 U.S. at 582. The Court then clarified 

the outer boundaries for such an award: “an award of more 

than four times the amount of compensatory damages might 
70 HARDEMAN V. MONSANTO

be close to the line of constitutional impropriety.” Id. 

However, it also emphasized an outermost limit in making 

such an award, stating “when compensatory damages are 

substantial, then a lesser ratio [less than 4:1], perhaps only 

equal to compensatory damages, can reach the outermost 

limit of the due process guarantee.” Id. (emphasis added).

The compensatory damages in this case are substantial 

($5,267,634.10) and the reasons to justify a higher ratio do 

not exist. Thus, a punitive damages amount equal to 

compensatory damages reaches the Supreme Court’s 

outermost limit for punitive damages.

The California Supreme Court provides further 

guidance, especially focusing on a case where there is a 

relatively low reprehensibility. It said that “a ratio of one to 

one might be the federal constitutional maximum in a case 

involving . . . relatively low reprehensibility and a 

substantial award of noneconomic damages: ‘When 

compensatory damages are substantial, then a lesser ratio, 

perhaps only equal to compensatory damages, can reach the 

outermost limit of the due process guarantee.’” Roby v. 

McKesson Corp., 219 P.3d 749, 769 (Cal. 2009) (quoting 

State Farm, 538 U.S. at 425). In this case, the district court 

reduced the jury’s 14.2:1 punitive damages award to nearly 

a 4:1 ratio, which is generally reserved for a higher degree 

of reprehensible conduct. Id. Monsanto’s conduct here did 

not include (1) acts or threats of violence; or (2) acts of 

trickery or deceit, evidencing a low degree of 

reprehensibility.

Even in a case that involved conduct that was highly 

reprehensible, the California Court of Appeal concluded that 

“the permissible ratio of punitive to compensatory damages” 

should be reduced when the noneconomic damages 

“appear[ed] to include a punitive component.” See 
HARDEMAN V. MONSANTO 71

Bankhead v. ArvinMeritor, Inc., 139 Cal. Rptr. 3d 849, 866–

67 (Ct. App. 2012) (allowing punitive damages award at a 

2.4:1 ratio). The Supreme Court agrees. See State Farm, 

538 U.S. at 425–26, 429 (explaining that “in light of the 

substantial compensatory damages awarded (a portion of 

which contained a punitive element), a punitive damages 

award at or near the amount of compensatory damages” was 

justified).

The jury awarded substantial past and future 

noneconomic damages totaling $5,066,667, which contain a 

punitive element. The district court recognized this fact 

when it noted that the $2,000,000 in future noneconomic 

damages was “borderline,” because it was “somewhat 

difficult to rationalize the conclusion that the suffering he 

will face is, effectively, two-thirds of the suffering he has 

already endured.” In re Roundup Prod. Liab. Litig. 385 F. 

Supp. 3d. at 1045. Thus, a punitive damages award of 3.8:1 

exceeded the constitutionally permissible limits. See State 

Farm, 538 U.S. at 425; Roby, 219 P.3d at 769. The ratio of 

punitive damages should be reduced to a 1:1 ratio. See id.

3. The difference between the punitive damages 

awarded and the civil penalties authorized or 

imposed in similar cases.

The third guidepost also supports punitive damages 

equal to the compensatory damages award. Sanctions for 

comparable misconduct can be determined by either the 

“civil or criminal penalties that could be imposed for 

comparable misconduct,” Gore, 517 U.S. at 583, or “the 

existence of other civil awards against the defendant for the 

same conduct,” Haslip, 499 U.S. at 22; see also Ismail v. 

Cohen, 899 F.2d 183, 186 (2d Cir. 1990) (“Reference to 

other awards in similar cases is proper.”).
72 HARDEMAN V. MONSANTO

One has difficulty comparing civil or criminal penalties 

with this punitive damages award. During the time 

Hardeman used Roundup, there were no federal or state 

criminal or civil penalties for Monsanto’s conduct. Neither 

the federal government nor the State of California had 

imposed any penalties for the possibility that glyphosate may 

cause cancer.4

 Although Monsanto’s conduct following the 

harm can be considered in setting the punitive damages 

award, see Johnson & Johnson Talcum Powder Cases, 

249 Cal. Rptr. 3d at 678, California did not list glyphosate as 

a chemical known to cause cancer until 2017.5 It is similarly 

difficult to determine how the federal government or 

California would apply or calculate fines (which is probably 

one of the reasons neither party really addressed this issue).

Comparing this case to the only other litigated case 

against Monsanto regarding the sale of Roundup supports a 

1:1 ratio. See Johnson v. Monsanto Co., 266 Cal. Rptr. 3d 

111, 135 (Ct. App. 2020). In Johnson, the plaintiff 

developed cancer in 2014 after using Roundup. Id. at 116–

17. Johnson sought damages, based on Monsanto’s 

knowledge regarding Roundup’s carcinogenicity. Id. at 117. 

4 Criminal and civil penalties may be imposed under federal and 

state law. See 7 U.S.C. §§ 136j(a)(1)(E), 136l(a)(1); 40 C.F.R. § 19.4; 

Cal. Health & Safety Code §§ 25249.6, 25249.7(a). Under federal law, 

civil penalties may be assessed up to $5,000 for each offense. 7 U.S.C. 

§ 136l(a)(1); see also 40 C.F.R. § 19.4 (2012). Criminal penalties may 

result in either imprisonment of one year, a $50,000 fine, or both. Id.

§ 136l(b)(1). California law imposes a civil penalty up to $2,500 per day 

for each violation. Cal. Health & Safety Code § 25249.7(a).

5 California Health & Safety Code section 25249.6 prohibits any 

“person in the course of doing business [from] knowingly and 

intentionally expos[ing] any individual to a chemical known to the state 

to cause cancer or reproductive toxicity without first giving clear and 

reasonable warning to such individual.”
HARDEMAN V. MONSANTO 73

Reviewing the evidence, the district court reduced 

compensatory damages to $10,253,309.32 and awarded 

punitive damages at a 1:1 ratio. Id. at 129. The damages 

awarded (for essentially “the same conduct”) in Johnson

provide a worthy comparison in assessing the 

constitutionality of this punitive damages award. See 

Haslip, 499 U.S. at 22; see also Restatement (Second) of 

Torts § 908 cmt. e (1979) (noting that “[i]t seems appropriate 

to take into consideration both the punitive damages that 

have been awarded in prior suits and those that may be 

granted in the future, with greater weight being given to the 

prior awards”).

Finally, our sister circuits have come to similar 

conclusions when dealing with substantial compensatory 

damages (even when the conduct is highly reprehensible). 

For example, in Boerner v. Brown & Williamson Tobacco 

Co., the Eighth Circuit concluded that, despite American 

Tobacco’s “highly reprehensible” conduct, the “punitive 

damages award [of $15,000,000] [wa]s excessive when 

measured against the substantial compensatory damages 

award [of $4,025,000].” 394 F.3d 594, 603 (8th Cir. 2005). 

Thus, it “conclude[d] that a ratio of approximately 1:1 would 

comport with the requirements of due process.” Id.; 

Saccameno v. U.S. Bank Nat’l Ass’n, 943 F.3d 1071, 1090 

(7th Cir. 2019), cert. denied sub nom. Saccameno v. Ocwen 

Loan Servicing, LLC, 140 S. Ct. 2674 (2020) (holding that 

“a considerable compensatory award for the indifferent, not 

malicious, mistreatment” and evidence that the “award 

reflects emotional distress damages that ‘already contain [a] 

punitive element’” “should not exceed 1:1”); Bridgeport 

Music, Inc. v. Justin Combs Pub., 507 F.3d 470, 490 (6th 

Cir. 2007) (“Given the large compensatory damages award 

of $366,939, a substantial portion of which contained a 

punitive element, and the low level of reprehensibility of 
74 HARDEMAN V. MONSANTO

defendants’ conduct, a ratio of closer to 1:1 or 2:1 is all that 

due process can tolerate in this case.”); see also Clark, 

436 F.3d at 607 (holding that “because the compensatory 

damage award here is not particularly large, a 1:1 ratio is 

inappropriate. But due to the lack of several of 

reprehensibility factors, any ratio higher than 2:1 is 

unwarranted”).

4. Conclusion:

I start where I began. Because we are mandated to 

review de novo the district court’s award of punitive 

damages, one must undertake the review. In light of the 

three guideposts, the district court’s $20,000,000 punitive 

damages award exceeds the line of constitutionality. The 

facts found by the district court do not support a 3.8:1 ratio 

to compensatory damages. Most notably, Monsanto’s 

conduct is not particularly reprehensible in light of the 

ongoing scientific debate. The compensatory damages are 

substantial; thus, punitive damages in an amount equal to 

compensatory damages reaches the outermost limit of the 

due process guarantee. Criminal and civil penalties and 

punitive damages awarded in other cases do not suggest a 

higher award. We then should go no further; this 

punishment will satisfy the State’s legitimate objectives for 

imposing such damages.