Epidemiology Expert’s Opinion on Religious Objection to COVID-19 Vaccine Excluded
Posted on August 6, 2025 by Expert Witness Profiler
Kevin McCormick has sued his former employer, the Chicago Transit Authority. During the COVID-19 pandemic, the CTA established a policy requiring its employees to be vaccinated against the virus. McCormick sought a religious-based exemption from the requirement. The CTA concluded that McCormick had not shown that his request for an exemption was actually religion-based and denied his request. When McCormick still declined to be vaccinated, the CTA terminated his employment. This lawsuit followed.
Both parties have named an expert to give opinion testimony at trial, and each has asked the Court to prevent the other’s expert from testifying.
Biology Expert Witness
Pamela Acker has an undergraduate degree in biology, earned in 2004, and while an undergraduate she was involved in genomics research on a particular topic for a year.
She pursued a master’s degree in biology at The Catholic University of America from 2010 through 2012 and was awarded that degree in 2012. During various periods while at Catholic University, Acker worked as a research assistant, a teaching assistant, and an adjunct instructor.
Acker taught high school biology for about six years and developed curricula for a homeschool co-op and for a Catholic homeschool organization for about three years.
Epidemiology Expert Witness
Mark A. Roberts is an epidemiologist who has worked for a little over fifty years in public health, occupational medicine, and academia. He has a master’s degree in education; a master’s of public health in epidemiology and biostatistics; a doctorate in epidemiology and biostatics; and he is a medical doctor. Roberts served as the State Epidemiologist for the State of Oklahoma. He has published numerous articles, books, and other materials in the field of epidemiology, he has taught graduate-level courses; and has been qualified to render expert testimony in a number of court cases. In addition, since the outset of the COVID- 19 pandemic, Roberts has consulted with about two dozen companies, organizations, agencies, law firms, and others regarding responses to issues related to COVID-19.
Get the full story on challenges to Mark Roberts’ expert opinions and testimony with an in-depth Challenge Study.
Discussion by the Court
Plaintiff’s Witness Pamela Acker
Acker intended to render opinions that: (1) aborted fetal cell lines were used in the development of the COVID-19 vaccine, and provided a detailed description of how they were purportedly used; (2) McCormick, as a practicing Roman Catholic, had a legitimate religious-based objection to the vaccine due to the use of aborted fetal cell lines (along with a detailed description of why this is so); (3) contentions that other medications that McCormick uses or has used similarly involved use of aborted fetal cell lines are inaccurate, along with an explanation of why; (4) the COVID-19 vaccine causes physical harm to vaccinees, and the vaccine does not prevent infection; and (5) McCormick’s proposed alternative to vaccination—wearing a facemask and keeping a distance from others—was an adequate alternative.
The CTA contended that Acker’s opinions should be barred because she is not sufficiently qualified by education, training, or experience to give expert testimony on any of the points in question, and because her opinions regarding the religious legitimacy of McCormick’s beliefs will not assist the jury in determining any fact in issue.
Analysis
Acker is not qualified to render opinion testimony at a trial regarding the basis or legitimacy of McCormick’s claimed religious beliefs regarding the COVID-19 vaccine or vaccines generally. She does not identify any more training or expertise in the field of Catholic doctrine or theology than the average Catholic generally, or at least no more than the average person who attended a Catholic university and, perhaps, took the undergraduate theology courses typically required at such universities for persons not majoring in theology. The Court has no doubt that Acker has read a lot about Catholic teaching, including as it applies to vaccines, but that—even together with the rest of her background—does not give her any specialized knowledge within the meaning of Rule 702 that qualifies her to render opinions on these topics.
Qualifications aside, any opinion by Acker on the sincerity of McCormick’s religious beliefs or whether those beliefs actually motivated his objection to getting vaccinated would amount to an opinion regarding his state of mind, which is generally an inappropriate topic for “expert” or other opinion testimony.
On the particular topics regarding which she proposes to opine—how the COVID-19 vaccine is made; how other vaccines are made; the effectiveness and effect of the vaccine; and the adequacy of McCormick’s proposed alternative to vaccination—the record is sufficiently clear that Acker derives her claimed expertise (and, it appears, her opinions) simply from compiling and reading material produced by others.
Defendant’s Witness Mark Roberts
Roberts’ report stated that he has “reached the overarching opinion that there is no objective, scientific evidence supporting McCormick’s claim of a religious exemption from the [CTA’s] COVID-19 vaccination requirements for its employees.”
To begin with, McCormick did not challenge Roberts’ scientific or medical qualifications or expertise. The Court concluded that he is qualified to render opinion testimony in the fields in which he has worked and taught.
McCormick asserted a claim under Title VII for failure to accommodate his religious beliefs. To prevail, he must establish that: (1) he had a belief or practice that was religious in nature and conflicted with an employment requirement; (2) he called this belief or practice to the CTA’s attention; and (3) his religious belief or practice was the basis for his discharge.
If McCormick establishes these elements, then the burden shifts to the CTA to show that it could not accommodate McCormick’s religious belief or practice without undue hardship.
Analysis
Let us focus on Roberts’ broader opinion that “there is no objective, scientific evidence supporting McCormick’s claim of a religious exemption” to the vaccination requirement. As McCormick pointed out, religious beliefs or practices do not need to be supported by scientific or objective evidence. The Court agreed and ruled that Roberts may not offer this opinion at trial.
First, his testimony about the prevalence and community spread of COVID-19 during the relevant time period and the consistency of the CTA’s vaccination mandate with CDC and OSHA guidance was held to be relevant and admissible on the question of undue hardship. Second, the same is true regarding the safety risk posed by McCormick’s noncompliance with the vaccination mandate.
The Court also declined to exclude Roberts’ testimony regarding how and to what extent fetal cell lines were used in the development and testing of the vaccine. After all, the CTA is entitled to challenge McCormick’s contention that his opposition to getting vaccinated was not actually religious-based.
However, Roberts may not render opinions or conclusions regarding the “consistency” or inconsistency of McCormick’s views or practices. On that point, which essentially amounts to an inference or conclusion to be drawn from other evidence (including testimony that Roberts will render), Roberts has no specialized expertise that exceeds that of a jury.
Held
The Court granted the Defendant’s motion to bar Plaintiff’s expert witness Pamela Acker and partially granted but largely denied the Plaintiff’s motion to bar Defendant’s expert witness Dr. Mark A. Roberts.
Key Takeaway:
Given her biology background, Acker no doubt has a greater degree of understanding of these materials than the average person. But simply compiling, reading, and rendering opinions and conclusion reached by others who themselves may have the required specialized training or experience—which is all that Acker’s expert disclosure reflects she has done—does not qualify one to testify as an expert under Rule 702.
Case Details:
| Case Caption: | McCormick V. Chicago Transit Authority |
| Docket Number: | 1:23cv1998 |
| Court Name: | United States District Court, Illinois Northern |
| Order Date: | August 04, 2025 |
