Plaintiff Leroy Jerome Richardson, III, a basketball referee, has sued his former employer, NBA Services Corp. and the National Basketball Association (together, the “NBA”) after his request for a religious exemption from its requirement that all NBA referees be vaccinated against COVID-19 during the 2021-22 season was denied.
The NBA filed a motion to exclude the testimony of the Plaintiff’s expert, Dr. Harvey Risch.
Epidemiology Expert Witness
Harvey A. Risch is a practicing epidemiologist with more than 40 years of research and teaching experience. He is a Professor Emeritus of Epidemiology at Yale School of Public Health.
The majority of his career has focused on cancer and its causation. In May 2020, he published a paper on early treatment of high-risk COVID-19 outpatients. Since that time, he has co-authored other papers on COVID-19, which he describes as focusing on early outpatient management.
Risch believes that the spread of infection is inevitable and post-infection natural immunity is a public good. He believes that the pandemic should not have been managed by tracking infection but rather by tracking deaths, hospitalization, and the incidence of serious long-term syndromes caused by infection. Accordingly, he asserts, governments, businesses and schools should not have mandated vaccination to prevent the spread of infection.
Insofar as the NBA is concerned, Risch observed that by December 2021, the NBA had added a booster dose requirement to its mandate. Nonetheless, NBA referees and players, almost all of whom were vaccinated, caught COVID-19 during the 2021-22 season. Risch concluded that, given the small number of NBA staff seeking a religious exemption, even if all had gotten COVID-19, the infection burden would have been less than the breakthrough infection burden among the vaccinated referees.
Relevance
The NBA argued that many of Risch’s opinions are irrelevant. According to the NBA, the issue for the jury will be whether it reasonably relied on health authority guidance for the 2021-22 season and has carried its burden to show that allowing exemptions to its vaccination policy would have imposed an undue hardship. Accordingly, the NBA sought to strike Risch’s disagreements with the advice given by government agencies regarding COVID-19 and the data presented by government health authorities. For instance, Risch took issue with whether the government data was accurate and argued that the government should have focused more on issues such as post-infection natural immunity or developed incentives for vaccination.
Although Risch is offered as a witness on the issue of undue hardship, he did not offer any opinion on the negative impact that game postponement, rescheduling, and cancellation would have on the NBA and those involved in NBA games. Nor did he dispute that the Omicron variant of the COVID-19 virus was considered even more transmittable than prior variants. His disagreements with public health management of the pandemic are irrelevant to the particular issues that created hardship for the NBA and the reasonableness of the NBA’s reliance on its experts in 2021 and 2022.
The NBA sought to strike as well those opinions which relied on studies published after the 2021-22 season as irrelevant to the NBA’s determination by December 2021 to insist that its referees be vaccinated.
Although Risch indicated that he is relying on later studies only to confirm his opinion, without those later studies it is unclear whether Risch had any reliable basis in the fall of 2021 for a different opinion than the one offered by the NBA’s medical consultants. The Court held that citing those later studies would only create confusion at best.
Legal Conclusion
The NBA additionally sought to exclude Risch’s report to the extent it offered legal conclusions. As an example of such inadmissible testimony, the NBA pointed to Risch’s opinion that allowing Richardson to work without a vaccination did not constitute an undue hardship when measured against the Equal Employment Opportunity Commission (“EEOC”) guidelines.
The NBA is correct that the Plaintiff’s expert cannot offer such opinions to the jury. In opposition to this motion, Richardson agreed that Risch cannot testify to the legal conclusions in his report.
Reliability
The NBA explained that Risch has rejected nearly all of the studies that were available during the 2021-22 season and has relied instead on a 2024 “pre-print” study — i.e., a study that is shared publicly but not peer-reviewed — to conclude that vaccinations were not as effective as they were believed to be through 2022.
The NBA also contended that Risch has selectively pointed to passages in studies to reach conclusions different from what the authors of the study concluded, and has done so without an adequate explanation.
In opposing this motion, Richardson pointed to only three studies that he argued are relevant and provide appropriate support for Risch’s opinion: Madewell, Puhach and the pre-print Riemersma.
While Madewell acknowledged that COVID-19 vaccines became less effective in reducing the spread of new variants, Risch distorted Madewell to cite it for the proposition that vaccines had “lost most of their ability” to suppress the spread of infection. Puhach was not published until March 2023 and therefore would not have been available to the NBA when it made its decision to no longer permit unvaccinated referees to work.
Finally, Riemersma, according to Risch, indicated that those infected during the period in which the Delta variant was prominent, had “similar” viral loads whether or not they had been vaccinated. That is an accurate description of Riemersma. But this study, which was not peer reviewed, does not undercut the advice the NBA’s experts provided to it, much less the recommendations of the Centers for Disease Control and Prevention (“CDC”). It does not take issue with the data showing that vaccination reduced the risk of infection.
In sum, the Court ruled that Risch’s opinions should also be excluded because they were not reliable.
Rule 403
Finally, the NBA argued that the report must also be stricken pursuant to Rule 403.
Risch’s analysis created a substantial risk of confusing and misleading the factfinder. In deciding whether the NBA has carried its burden of showing that an accommodation of Richardson would have created an undue hardship, jurors must focus on what the relevant scientific community and the NBA understood of the COVID-19 virus and the efficacy of vaccines and testing in the 2021-22 season, particularly during the late fall of 2021.
The Court held that Risch’s criticism of public health authorities’ recommendations in the midst of a pandemic, especially when based on a few hand-picked studies that post-date the period in which the NBA made its decision, has limited to no probative value.
Held
The Court granted the Defendants’ motion to exclude the testimony of the Plaintiff’s expert, Dr. Harvey Risch.
Key Takeaway:
While cross-examination is an appropriate method for demonstrating the limitations in an expert’s analysis, before that analysis may be admitted at trial, its proponent must still show that it is sufficiently reliable to pass muster under Rule 702 and Daubert. This Richardson has not done.
Admission of Risch’s testimony risks misleading and confusing the jury as to the relevant standard for determining undue hardship and the relevant evidence on which to base its verdict.
Case Details:
Case Caption:
Richardson V. The National Basketball Association Et Al
Board of Education of the City of St. Louis, through Superintendent Kelvin Adams and Chief Human Resources Officer Charles Burton, imposed a vaccination mandate on its employees. Despite inviting requests for religious exemptions (and received nearly 200 of them), it denied every single one of them. As a result, many of the employees brought this suit against the Board, Adams, and Burton.
Defendants retained Dr. Daniel Salmon to provide opinions in six general areas: (1) the threat of COVID-19 in October 2021, (2) the “[s]afety and [e]fficacy of COVID-19 vaccines,” (3) institutions’ COVID-19 vaccine mandates, (4) the “[i]mpact of medical and religious exemption requests,” (5) “the anti-vaccine movement’s impact on mandatory vaccine policies,” and (6) the connection between COVID-19 vaccines and stem cells. Plaintiffs filed a motion to exclude the proposed testimony of Salmon.
Epidemiology Expert Witness
Daniel Salmon works as a professor of global disease epidemiology and control in the Department of International Health at the Johns Hopkins University Bloomberg School of Public Health.
The Plaintiffs argued Salmon lacked knowledge about the specific parties in the case, noting he reviewed only three exhibits and didn’t know the number of exemption requests.
The Court held that these objections did not warrant dismissing Salmon’s opinions wholesale.
2. Relevance
Plaintiffs argued that Salmon’s opinions lacked relevancy because they did not relate to Defendants’ stated reasons for denying Plaintiffs’ religious exemption requests. After all, the only reason that Defendants gave for denying Plaintiffs’ exemption requests was the need to “balance the constitutional obligation to provide a free public education” to Missouri youth against the right to the free exercise of religion.
Plaintiffs thus argued that any other attempted justification for the denials bears no relevance to the case because “[g]overnment ‘justification[s]’ for interfering with First Amendment rights ‘must be genuine, not hypothesized or invented post hoc in response to litigation.’”
The letters denying the religious-exemption requests did not explicitly mention the Board’s interest in protecting students and staff from COVID-19. But the challenged vaccination policy itself did. Basically, the Board of Education adopted this policy to safeguard the health and well-being of employees and their families.
Therefore, the post-hoc-in-response-to-litigation doctrine did not render Salmon’s opinions irrelevant.
3. Assistance to the Trier of Fact
Plaintiffs argued that Salmon’s opinions “expressed factual determinations that a jury is readily capable of making without expert assistance” and that his opinions “are premised on publicly available information regarding the COVID-19 pandemic.”
However, the Court rejected Plaintiffs’ argument on this ground as undeveloped.
4. Relevance and Unfair Prejudice
Plaintiffs argued that Salmon’s testimony would be “unfairly prejudicial” because it would associate Plaintiffs “with anti-vaccine movements and statements about stem cells.” Salmon admitted that he “[doesn’t] know anything about the Plaintiffs in this case.”
The Court agreed with Plaintiffs that Salmon’s opinions about the anti-vaccine movement’s impact on mandatory vaccine policies would not help the jury. After all, Salmon can offer nothing of value on the question of whether Plaintiffs’ objections were “religious in nature.”
So although Salmon might have knowledge about anti-vaccine movements, he does not (and cannot) connect any Plaintiff to any anti-vaccine movement.
Plaintiffs alleged in their complaint that their “religious beliefs prevented them from receiving the vaccination due to their use of fetal stem cells taken from aborted fetuses.”
As for Salmon’s opinions about stem cells and stem cells’ connection to COVID-19 vaccines, Salmon did not (and could not) opine on the extent to which the stem-cell issue influenced Plaintiffs’ objections to COVID-19 vaccination since he didn’t know anything about Plaintiffs.
5. Legal Conclusions
Salmon’s report answers this question: “Did institutions have a responsibility to evaluate non-medical exemption requests rather than simply rubber-stamping requests?” Salmon did not explain what he meant by “responsibility.”
To the extent that Salmon attempted to characterize “responsibility” as legal obligation, the Court excluded Salmon’s testimony as an improper legal opinion.
And to the extent that Salmon attempted to characterize “responsibility” in a different way (e.g., as moral or ethical responsibility), Defendants have failed to establish that Salmon has expertise to render opinions in that domain, and they have also failed to identify any reason why any opinions about moral or ethical responsibilities—as opposed to legal obligations—would have any relevance to the issues in this case.
Therefore, the Court excluded Salmon’s testimony to the extent that Salmon sought to testify to institutional responsibility of evaluating non-medical exemption requests.
6. Expertise
Plaintiffs argued, once again, that Salmon “did not apply any specialized expertise to the evidence.” The Court disagreed. Salmon’s expert report showed that he largely reached his conclusions based on his assessment, interpretation, and synthesis of numerous scientific studies related to vaccinology and epidemiology.
And Plaintiffs have failed to point to any specific opinions that they believe Salmon reached without his expertise. The Court rejects Plaintiffs’ generic, undeveloped argument on this ground.
Held
The Court granted in part and denied in part the Plaintiffs’ motion to exclude the testimony of Daniel Salmon.
Key Takeaway:
Salmon does not (and cannot) opine on the extent to which the stem-cell issue influenced Plaintiffs’ objections to COVID-19 vaccination because objective facts about the vaccines’ connections to stem cells have no bearing on whether Plaintiffs objected to vaccination based on their religious beliefs, which “need not be acceptable, logical, consistent, or comprehensible to others” to merit protection under the law.
Case Details:
Case Caption:
Brandon V. Board of Education of City of ST. Louis
Docket Number:
4:22 cv 00635
Court Name:
United States District Court for the Eastern District of Missouri, Eastern Division
Washington Governor Jay Inslee issued Proclamation 21-14 (“the Proclamation”), which required state employees to be fully vaccinated by October 18, 2021, to continue employment with the state. The Proclamation carved out an exception to the vaccination requirement for employees who were entitled to disability related accommodations or accommodations related to a sincerely held religious belief under relevant anti-discrimination laws, including Title VII and the Washington Law Against Discrimination (“WLAD”).
This litigation concerns a number of Plaintiffs who requested religious accommodations from the Washington State Department of Fish and Wildlife (“WDFW”).
While the Plaintiffs were initially granted religious accommodations, they were informed in late September of 2021 that “no reasonable accommodation” could be found because their jobs “must at times be done in the physical presence of others.” The Plaintiffs were subsequently terminated in November of 2021.
Harvey Risch is a practicing epidemiologist with more than 40 years of research and teaching experience. He is a Professor Emeritus of Epidemiology at Yale School of Public Health.
Lisa Brock has worked in human resources (“HR”) for over forty years. She spent the majority of her career in healthcare. Most recently, she worked as the HR director at Overlake Medical Center and Clinics.
John R. Cary is a certified rehabilitation counselor (CRC) and disability management specialist (CDMS) with over 19 years of experience in providing rehabilitation counseling and case management services to individuals facing socio-economic and psychosocial challenges, multiple morbidities, and language barriers.
Risch submitted two expert reports—one on the efficacy of COVID-19 vaccines and vaccine mandates and one rebuttal report.
In the rebuttal report, Risch opined that the vaccine mandate failed to recognize that “post infection natural immunity” is as good as if not better than vaccination.
Defendants objected to Risch’s opinions on the efficacy of COVID-19 vaccines, the role of natural immunity, and the Proclamation.
Relevancy
To begin with, Defendants maintain that “Risch’s opinions on the efficacy of COVID-19 vaccines, the role of natural immunity, and the Proclamation should be excluded for lack of relevancy,” as they will not assist the trier of fact in understanding “a fact in issue.”
The Court concluded that Risch’s testimony about the efficacy of COVID-19 vaccines, the role of natural immunity, and the governor’s Proclamation requiring vaccination will be excluded for lack of relevance.
Facial challenges to the Proclamation have been rejected and the vaccine mandate itself is not at issue in this litigation—only how WDWF applied it to its employees. Accordingly, the Court held that testimony about the efficacy of the Governor’s vaccine mandate will not aid the “trier of fact to understand the evidence or to determine a fact in issue.”
Moreover, Defendants argued that his opinions based on “information available after WDWF made accommodation decisions regarding Plaintiffs” must be excluded as not relevant.
Besides, Defendants added that judging an employer’s undue hardship decision based on knowledge and information developed after the fact would hold that employer to an impossible standard. Risch asserted that WDFW cannot establish undue hardship because “the cumulative hardship would not have been inordinate compared to the larger breakthrough infection burden from the vaccinated staff.”
Likewise, the Court excluded Risch’s conclusions about whether Defendants provided a reasonable accommodation or established undue hardship.
Reliability
Defendants argued that Risch’s opinions are not the product of reliable principles and methods because he does not state “what method of analysis he applies to any of the data he includes in his report.”
As to Risch’s opinions about the risk of breakthrough infections, Defendants argued that he “fails to compare apples to apples.”
In determining the number of WDWF employees who could have been expected to have breakthrough infections, Risch used CDC figure of 4.3%. The 4.3% figure represented the total number of vaccinated breakthrough cases by the total number of vaccinated people from April 2021 to December 2021: 5,988,636 divided by 139,768,554.
The Court held that not only were Risch’s calculations incorrect, but Risch offered no information or analysis comparing the job duties and responsibilities of the hypothetical employees who would suffer a breakthrough infection with those of the unvaccinated employees. For example, it is unknown whether any of these hypothetical employees teleworked full-time or otherwise interacted with co-workers or the public.
Thus, even if there were hypothetical employees who suffered breakthrough infections, it impossible to evaluate whether those hypothetical employees would have, or would not have, posed a greater risk than the unvaccinated Plaintiffs in this case.
Furthermore, the Court determined that Risch’s opinion about the 4.3% figure—that it “is also likely a very large undercount” is unreliable, as Risch does not cite any peer reviewed evidence or statistical analysis that suggests that the CDC figure is an undercount or account for whether CDC itself corrected for the factors Dr. Risch opines resulted in the undercount.
Lisa Brock
In her report, Brock included a step-by-step best practices guide published by the Society for Human Resources Management (SHRM) on handling requests exemptions to a vaccine requirement. She testified that her professional opinion in the report is based on her experience as a “practitioner of human resources,” and specifically the experience she gained as an “HR practitioner during the time of the proclamation and the COVID vaccine.”
Defendants asserted that “despite her failure to engage in a comprehensive review of any Plaintiff’s accommodation process, Brock made several unsupported factual conclusions regarding WDFW’s accommodation process and also made impermissible legal conclusions.”
The Court held that Brock relied on her personal experience and a paucity of documents to evaluate WDFW’s accommodations process. This extremely limited evidence did not “provide a complete picture of relevant events”—indeed, Brock did not review any documents specific to more than half of the Plaintiffs going to trial and did not review the accommodations policies that WDFW had in place.
The Court excluded Brock’s report because she offered opinions without a full understanding or knowledge of the facts of this case.
John Cary
On January 31, 2025—the final day of discovery—Plaintiffs submitted an expert rebuttal report from John Cary. The rebuttal deadline had been extended at the Parties request to January 14, 2025.
Rule 37 forbids the use of Cary’s expert report unless Plaintiffs are able to show that the failure was substantially justified or harmless. Plaintiffs could have requested leave from the Court for late supplementation but did not. Plaintiffs could have notified Defendants and the Court during the discovery hearing on January 30, 2025, but did not. Accordingly, the Court excluded Cary’s expert report.
Held
The Court granted the Defendants’ motions to exclude the opinions of Dr. Harvey Risch, Lisa Brock and John Cary.
Key Takeaway:
The Court held that Risch did not base his critiques of the CDC’s methods in widely accepted scientific methods of analysis—and failed to explain the analytical method he is using.
Brock relied on her personal experience and a paucity of documents to evaluate WDFW’s accommodations process. Accordingly, because Brock’s testimony lacks support from sufficient facts or data and fails to sufficiently specify the method by which she reached her conclusions, the testimony does not satisfy the Daubert standard.
Case Details:
Case Caption:
Shirley Et Al V. Washington State Department Of Fish And Wildlife Et Al
This is a multidistrict litigation (“MDL”) in which over 5,000 individual Plaintiffs allege that they developed Parkinson’s disease because of their exposure to an herbicide, paraquat dichloride (“paraquat”). Paraquat is a restricted-use quaternary ammonium herbicide that is used to control weeds in farming operations and other settings around the United States. Defendants, Syngenta Crop Protection, LLC and Syngenta AG (collectively “Syngenta”), currently manufacture and distribute paraquat for use in the United States, whereas Defendant, Chevron U.S.A., Inc. (“Chevron”), manufactured and distributed paraquat until 1986.
Facts of the Case
Dr. Martin Wells serves as Plaintiffs’ sole expert witness on the critical issue of general causation, offering an opinion that occupational exposure to paraquat can cause Parkinson’s disease. Defendants filed a motion to exclude Wells’ proffered testimony which raised complex issues related to the study of epidemiology and the scientific methodologies of systematic review and meta-analysis. Defendants’ motion is brought in four of the six member cases that were selected for case-specific discovery in the Court’s April 13, 2022 order. These four cases have gone through fact and expert discovery and now serve as this MDL’s first set of trial selection cases.
Plaintiffs retained Martin Wells to “analyze the epidemiological evidence relating the association and causation of the occupational exposure of paraquat to the onset of Parkinson’s disease.” To accomplish this task, Wells conducted a meta-analysis of seven epidemiological studies that measured a potential association between paraquat and Parkinson’s disease. Wells determined, based on this meta-analysis, that there was a “near tripling of PD occurrence in [study] participants occupationally exposed to paraquat.”
After establishing a positive association between occupational exposure to paraquat and Parkinson’s disease, Wells conducted a weight of the evidence review to determine whether the association was attributable to a causal relationship. He found that it was and drew the following conclusions: (i) the available epidemiological evidence supports a causal relationship between paraquat and Parkinson’s disease; and (ii) the trial selection Plaintiffs fit the exposure and diagnostic criteria of the seven studies in his meta-analysis, meaning that they were at “near tripl[e]” the risk of developing Parkinson’s disease.
Epidemiology Expert Witness
Dr. Martin Wells boasts of an impressive career as an academic, researcher, and prolific publisher in the fields of biostatistics and epidemiology. He received his Ph.D. in Mathematics from the University of California in 1987 and became an Assistant Professor at Cornell University that same year. Furthermore, Wells currently serves as a Professor of Clinical Epidemiology and Health Services Research at Weill Medical School and as the Chair of the Department of Statistics and Data Science at Cornell. Moreover, he has published 250 scholarly articles on statistics, human health, and other topics and has received research grants from numerous governmental and non-governmental institutions, including the U.S. Department of Agriculture, the U.S. Army, and the National Institutes of Health.
In his own words, Wells offers an opinion that “the available epidemiological evidence supports a causal relationship between occupational paraquat exposure and PD.”
(a) the expert’s scientific, technical, or other specialized knowledge will help the trier of fact to understand the evidence or to determine a fact in issue;
(b) the testimony is based on sufficient facts or data;
(c) the testimony is the product of reliable principles and methods; and
(d) the expert’s opinion reflects a reliable application of the principles and methods to the facts of the case.”
Amended Rule 702
This amended version of Rule 702 took effect on December 1, 2023, after the Parties submitted their briefing. The Advisory Committee on the Rules of Evidence explained that the amendment does not “impose[] any new, specific procedures.”
Rather, the amendment emphasized that the proponent bears the burden of demonstrating compliance with Rule 702 by a preponderance of the evidence, and that “each expert opinion must stay within the bounds of what can be concluded from a reliable application of the expert’s basis and methodology.”
The Advisory Committee cautions that “expert testimony may not be admitted unless the proponent demonstrates to the court that it is more likely than not that the proffered testimony meets the admissibility requirements set forth in [Rule 702].”
In providing this instruction, the Advisory Committee noted that some courts had “incorrect[ly]” held that an expert’s basis of opinion and application of her methodology were questions of weight, not admissibility. The Advisory Committee thus appears to have found that courts had erroneously admitted unreliable expert testimony based on the assumption that the jury would properly judge reliability by assigning appropriate weight to an expert’s opinion.
Bradford Hill Analysis
To judge causation, researchers ordinarily consider how the following nine “Bradford Hill” factors (named after the British epidemiologist and statistician, Sir Austin Bradford Hill) apply to an observed association:
(1) temporal relationship (the exposure must occur before the disease develops);
(2) strength of association (the higher the RR or OR, the greater the likelihood that the relationship is causal);
(3) dose-response relationship (whether a higher dose increases the incidence or severity of the disease);
(4) replication of findings (whether research findings have been replicated in different populations with consistent results);
(5) biological plausibility (whether the association is consistent with current biological knowledge about the disease);
(6) consideration of alternative explanations (whether the research has properly accounted for bias and confounding variables);
(7) cessation of exposure (whether the cessation of exposure reduces the risk of disease);
(8) specificity of association (an association is specific and more likely to be causal if the exposure is associated with only a single or a small number of diseases); and
(9) consistency with other knowledge (whether a causal inference is consistent with relevant general knowledge or data).
After establishing a positive association, Wells conducted a Bradford Hill analysis to determine whether occupational exposure to paraquat was causally related to Parkinson’s disease. Wells discussed six of the nine Bradford Hill factors (strength of association, consistency, temporality, dose-response, experimental evidence regarding the cessation of exposure, and specificity) in his first report, and assumed that the other three factors (biological plausibility, coherence, and analogy) were satisfied based on the report of Plaintiffs’ toxicology expert. He appears to have found that the six factors he evaluated were all satisfied, and on that basis, concluded that “drawing general causal inferences related to occupational paraquat exposure and PD is merited.”
Legal Analysis
A. Qualifications
Defendants first attacked Wells on the basis that he was not qualified to offer an opinion about the causal relationship between occupational paraquat exposure and Parkinson’s disease. This argument purported to show that although Wells possessed impressive credentials as a statistician, his qualifications were limited to just that type of work—calculating a summary risk estimate from a pre-selected universe of epidemiological studies.
The Court held that Wells is not just a statistician; he is a professor of epidemiology with an impressive record of scholarly publications on epidemiological issues. As such, he is well-equipped to judge the relative quality of the epidemiological studies at issue.
Simply put, as a biostatistician and epidemiologist, Wells is well qualified to offer a general causation opinion based on a Bradford Hill analysis and to evaluate the relative quality of epidemiological studies relevant to the causation question at issue.
B. Reliability
1.The Scope of Dr. Wells’ General Causation Opinion
An epidemiological causation assessment ordinarily proceeds in two steps: (i) a determination of whether a disease is associated with exposure to a particular agent; and (ii) if a positive association is found, a Bradford Hill analysis to determine whether the association is the result of a cause-and-effect relationship. At a high level, Wells followed these steps as well. First, he surveyed the epidemiological literature and established a positive association by conducting a meta-analysis of seven case-control studies that examined a possible association between paraquat exposure and Parkinson’s disease. Second, he conducted a Bradford Hill/weight of the evidence analysis to determine whether the totality of the evidence supported a causal relationship between occupational paraquat exposure and Parkinson’s disease. Wells then offered the opinion that the elevated odds ratio from his meta-analysis applied to the four trial selection Plaintiffs, Mr. Richter, Mr. Burgener, Mr. Fuller, and Mr. Coward.
Wells offered an expert opinion that “occupational” paraquat exposure was causally related to Parkinson’s disease. Any exposure that did not qualify as “occupational” is therefore not within the scope of his opinion. The Court observed that Wells redefined “occupational” exposure no less than three times, creating more questions than answers about the types of paraquat exposures that, according to him, can cause Parkinson’s disease.
2. Wells’ Meta-Analysis
Wells’ violations of the rules of meta-analysis are evident from the very beginning of his process. One of the initial steps in a meta-analysis involves the search for relevant studies that are then further analyzed for potential inclusion in the analysis. Wells’ first report is entirely devoid of a search narrative that would allow other researchers to validate his process.
The next methodological red flag in Wells’ meta-analysis is that until he submitted his rebuttal report, he failed to clearly articulate the inclusion/exclusion criteria that purportedly governed a study’s eligibility for his analysis. Indeed, Wells testified at his first deposition that he reviewed the relevant studies “holistically” to determine “whether or not [they were] reliable enough for inclusion.” This “holistic” approach was neither reduced to writing, nor did it offer any discernible objective criteria that would allow others to replicate Wells’ eligibility determinations.
Moreover, Wells relied on an evolving set of quality criteria to determine which studies ultimately warranted inclusion in his meta-analysis. This alone undermines the methodological soundness of his qualitative evaluation of the literature.
Another methodological issue in Wells’ meta-analysis concerned his apparent failure to follow even his own articulated reliability standards. Wells appeared to have violated this guideline for the most important study in his meta-analysis, Liou (1997).
The Court took no position on the relative merit of the various epidemiological studies at issue in Wells’ analysis. Indeed, the Court did not find Wells’ meta-analysis unreliable because it excluded van der Mark (2014), Shrestha (2020), or any other relevant study for that matter. Rather, Wells’ meta-analysis did not pass muster under Rule 702 because its methodology was unclear, inconsistently applied, not replicable, and at times transparently reverse-engineered.
3. Dr. Wells’ Weight of the Evidence / Bradford Hill Analysis
a. General Observations
After he generated his odds ratio of 2.8, Wells conducted a “weight of the evidence” review utilizing the Bradford Hill framework to determine whether the association was attributable to a cause-and-effect relationship between occupational paraquat exposure and Parkinson’s disease. This analysis involved the “combination of two methods”—weight of the evidence review and application of the Bradford Hill factors. Although this approach is generally reliable, there is “very little” circuit-level authority guiding its application in toxic tort cases.
In short, experts in toxic tort actions commonly employ this methodology to answer complex epidemiological causation questions. Because of its widespread adoption in the scientific community and in other litigations, the general reliability of this approach is not in dispute. However, the method gives researchers significant flexibility to decide how to analyze the evidence and weight each Bradford Hill factor in relation to the others. An expert could “theoretically assign the most weight to only a few factors, or draw conclusions about one factor based on a particular combination of evidence.” So, while the methodology offers the benefit of flexibility, it is vulnerable to results-driven analysis, which, of course, raises significant reliability concerns.
b. The Reliability of Dr. Wells’ Bradford Hill Analysis
Wells’ weight of the evidence/Bradford Hill analysis is a textbook example of the type of standardless presentation of evidence that courts have cautioned against. The most obvious methodological defect is the absence of any discernible weighting methodology. Neither Wells’ first report nor his rebuttal report offer any explanation of the relative weight or importance assigned to each of the six Bradford Hill factors he analyzed.
c. Isolation from the Scientific Community
This Court has focused, as it must, on the methodological soundness of Wells’ analyses in support of his conclusions, not the conclusions themselves. However, the line between methodology and conclusion is “not always an easy [one] to draw.”
Daubert expressly addressed the importance of independent validation of an expert’s opinion when it observed that “[w]idespread acceptance can be an important factor in ruling particular evidence admissible.” The Advisory Committee on the Federal Rules of Evidence therefore cautions that “when an expert purports to apply principles and methods in accordance with professional standards, and yet reaches a conclusion that other experts in the field would not reach, the trial court may fairly suspect that the principles and methods have not been faithfully applied.”
In conclusion, Wells’ causation theory has not been adopted or independently validated in any peer-reviewed scientific analysis outside of this litigation.
4. Dr. Wells’ Plaintiff-specific Opinions
Wells’ third and final proffered opinion concerned the individual Plaintiffs in the four trial selection cases, Mr. Burgener, Mr. Coward, Mr. Fuller, and Mr. Richter. According to Wells, “these individuals fit the inclusion criteria in the referenced seven studies in my meta-analysis.” As a result, “[t]he elevated odds ratio of 2.8[] and the [Bradford] Hill criteria apply to these individuals.”
This opinion will be excluded because it is not severable from Wells’ meta-analysis and his weight of the evidence/Bradford Hill analysis. Plaintiffs conceded this point at the Daubert hearing by noting that Wells’ meta-analysis is “critical for specific causation.” Moreover, without testimony concerning (i) a positive association between occupational paraquat exposure and Parkinson’s disease, and (ii) a causal relationship between occupational paraquat exposure and Parkinson’s disease, there is no testimony for Wells to give as it pertains to the four trial selection Plaintiffs.
Held
To sum it up, the Court concluded that Martin Wells’ proffered opinions were not admissible under Federal Rule of Evidence 702 and Daubert v. Merrell Dow Pharmaceuticals, Inc., 509 U.S. 579, 113 S. Ct. 2786, 125 L. Ed. 2d 469 (1993).
Key Takeaways:
Moreover, in addition to the Bradford Hill factors of strength of association, consistency, and temporality (which he also considered in Monroe), Wells discusses experimental evidence related to the cessation of exposure, evidence of a dose-response relationship, and specificity. Nonetheless, the Court is not persuaded that his discussion of these considerations pushes his testimony beyond the limits of his qualifications as a biostatistician and epidemiologist. Furthermore, Wells’ Bradford Hill analysis is appropriately limited to the epidemiological studies he reviewed. He does not purport to venture into the realm of toxicology or other disciplines that are beyond his area of expertise.
Wells’ reliance on an unwritten, “holistic” methodology presents an ideal example of “because I said so” expertise that is impermissible under Rule 702. Wells insisted that he “ha[s] the credentials to do this” and that he “had a process that [he] followed.” But these assurances, without more, do not show that Wells faithfully applied the necessary steps of his chosen methodology as Daubert requires.
Against the backdrop of Wells’ departure from the most basic methodological requirements of a weight of the evidence review, it is not surprising that his analysis reveals extensive selection bias. Wells appears to have fallen prey to the temptations of selection bias in his discussion of several Bradford Hill factors, most notably those concerning a dose-response relationship and strength of association.
Case Details:
Case Caption:
Richter v. Syngenta AG (In re Paraquat Prods. Liab. Litig.)
