JAMES DEW v. DU PONT DE NEMOURS AND COMPANY (2026)

ORDER

On July 13, 2026, trial will begin in this case. See [D.E. 286] 1. On April 17, 2026, trial plaintiffs Patsy Davis, Richard Davis, Annie Stevens, John Stevens, Allison Pini, and Sandra Riggins Branch (collectively, “plaintiffs”) and defendants E.I. Du Pont De Nemours and Company (“DuPont”), The Chemours Company, and The Chemours Company FC, LLC (collectively, “defendants”) moved to exclude the report and testimony of expert witnesses.

Plaintiffs move to exclude the testimony of defendants' epidemiological expert Dominik D. Alexander, Ph.D. (“Alexander”) [D.E. 288] and filed a memorandum in support [D.E. 289]. See Fed. R. Evid. 702. Plaintiffs also move to exclude the expert opinions of defendants' experts Michael Keinath, P.E. (“Keinath”) and Brent L. Finley, Ph.D. (“Finley”) or to present additional expert testimony to respond to certain opinions of Keinath and Finley [D.E. 290] and filed a memorandum in support [D.E. 292]. See Fed. R. Civ. P. 37(c). On May 1, 2026, defendants responded in opposition [D.E. 303, 304].

Defendants move to exclude the report and testimony of plaintiffs' experts Adam M. Domanski, Ph.D. (“Domanski”) [D.E. 291], Owen W. Duckworth, Ph.D. (“Duckworth”) [D.E. 294], Steven J. LaRosa (“LaRosa”) [D.E. 296], and Jamie C. DeWitt, Ph.D. (“DeWitt”) [D.E. 298], and filed memoranda in support [D.E. 293, 295, 297, 299]. See Fed. R. Evid. 702. On May 1, 2026, plaintiffs responded in opposition [D.E. 300, 301, 302, 305]. On July 1, 2026, defendants moved for leave to supplement the record with new evidence supporting their motion to exclude Domanski's report and testimony [D.E. 388, 391], and filed a memorandum in support [D.E. 389]. On July 2, 2026, the parties notified the court that the parties have stipulated that Keinath and Ruth Albright will not be trial witnesses [D.E. 393]. On the same day, plaintiffs responded in opposition to defendants' motion to supplement the record [D.E. 394]. As explained below, the court grants plaintiffs' motion to exclude Alexander's opinion about county-level cancer incidence data, grants in part and denies in part plaintiffs' motion to exclude Finley, grants defendants' motion to supplement the record, and denies defendants' motions to exclude Domanski, Duckworth, LaRosa, and DeWitt.

I.

Federal Rule of Evidence 702 governs the admission of expert testimony. See Fed. R. Evid. 702; Kumho Tire Co. v. Carmichael, 526 U.S. 137, 141–42 (1999); Gen. Elec. Co. v. Joiner, 522 U.S. 136, 142–43 (1997); Daubert v. Merrell Dow Pharms., Inc., 509 U.S. 579, 588 (1993); Engilis v. Monsanto Co., 151 F.4th 1040, 1046–50 (9th Cir. 2025); United States v. Forrest, 429 F.3d 73, 80–81 (4th Cir. 2005); Silicon Knights, Inc. v. Epic Games, Inc., No. 5:07-CV-275, 2011 WL 6748518, at *5–6 (E.D.N.C. Dec. 22, 2011) (unpublished). Rule 702 provides:

A witness who is qualified as an expert by knowledge, skill, experience, training, or education may testify in the form of an opinion or otherwise if the proponent demonstrates to the court that it is more likely than not that:

(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.

Fed. R. Evid. 702. “In 2023, Rule 702 was amended to clarify that the proponent of expert testimony bears the burden of establishing its admissibility and to emphasize that an expert's opinion must stay within the bounds of a reliable application of the expert's basis and methodology.” EcoFactor, Inc. v. Google LLC, 137 F.4th 1333, 1339 (Fed. Cir. 2025); see also Fed. R. Evid. 702 advisory committee's note to 2023 amendment (stating that the 2023 amendment is intended “to emphasize 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”).

Rule 702 “assign[s] to the trial judge the task of ensuring that an expert's testimony both rests on a reliable foundation and is relevant to the task at hand.” Daubert, 509 U.S. at 597; see Engilis, 151 F.4th at 1046–50; Cooper v. Smith & Nephew, Inc., 259 F.3d 194, 199–203 (4th Cir. 2001). In other words, Rule 702 requires that a trial judge “ensure that any and all scientific testimony or evidence admitted is not only relevant, but reliable.” EcoFactor, 137 F.4th at 1339 (cleaned up); see Daubert, 509 U.S. at 597–98; Engilis, 151 F.4th at 1046–50. Determining admissibility, which falls within the gatekeeping role of the court, is separate from determining “weight and credibility, which are within the province of the jury in a jury case.” EcoFactor, 137 F.4th at 1339; see Sommerville v. Union Carbide Corp., 149 F.4th 408, 423–27 (4th Cir. 2025).

The proponent of expert testimony must establish its admissibility by a preponderance of the evidence. See Fed. R. Evid. 702, 104(a); Daubert, 509 U.S. at 592 n.10; Engilis, 151 F.4th at 1048–50; Cooper, 259 F.3d at 199; see also Huddleston v. United States, 485 U.S. 681, 687 n.5 (1988); Bourjaily v. United States, 483 U.S. 171, 175 (1987). Expert testimony is appropriate when it “will help the trier of fact to understand the evidence or to determine a fact in issue.” Fed. R. Evid. 702(a). A district court may permit a witness qualified by knowledge, skill, experience, training, or education to testify and state an opinion where the testimony will help the trier of fact understand the evidence or determine a fact in issue and “([1]) the testimony is based on sufficient facts or data, ([2]) the testimony is the product of reliable principles and methods; and ([3]) the expert's opinion reflects a reliable application of the principles and methods to the facts of the case.” Fed. R. Evid. 702(b)–(d). Courts have distilled Rule 702's requirements into three crucial inquiries: (1) whether the proposed expert witness is qualified; (2) whether the proposed testimony is relevant; and (3) whether the proposed testimony is reliable. See Kumho Tire Co., 526 U.S. at 141; Daubert, 509 U.S. at 589; Engilis, 151 F.4th at 1048–50; Forrest, 429 F.3d at 80. The trial court must perform its special gatekeeping obligation concerning these three requirements. See, e.g., Fed. R. Evid. 702; Kumho Tire Co., 526 U.S. at 147; Engilis, 151 F.4th at 1048–50.

When a party challenges an expert's testimony, the court must “satisfy itself that the proffered testimony meets the relevant standard as a precondition to admissibility.” Snell v. Reid, No. 22-1869, 2024 WL 2815061, at *3 (4th Cir. June 3, 2024) (per curiam) (unpublished) (cleaned up); see Engilis, 151 F.4th at 1048–50; Sardis v. Overhead Door Corp., 10 F.4th 268, 282 (4th Cir. 2021). The court must make explicit findings concerning the challenged preconditions of admissibility either by written order or orally on the record. See Snell, 2024 WL 2815061, at *3; Sardis, 10 F.4th at 283; United States v. Smith, 919 F.3d 825, 835–36 (4th Cir. 2019).

As for qualification, an expert may be qualified based on “knowledge, skill, experience, training, or education.” Fed. R. Evid. 702. A court assesses qualifications in reference to the matter to which the witness seeks to testify. See Daubert, 509 U.S. at 591–93; Gladhill v. Gen. Motors Corp., 743 F.2d 1049, 1052 (4th Cir. 1984). The witness need not be the most well-known or well-qualified witness. See Gladhill, 743 F.2d at 1052. Nonetheless, a witness does not become an expert simply by claiming to be an expert or because some other court permitted the witness to testify as an expert. See, e.g., Thomas J. Kline, Inc. v. Lorillard, Inc., 878 F.2d 791, 799–800 (4th Cir. 1989) (holding that a witness with an MBA was not qualified to provide expert opinion testimony on complex economic antitrust matters about which the witness was not qualified by training, experience, or education); United States v. Bahena, 223 F.3d 797, 809–10 (8th Cir. 2000) (holding that a witness who held himself out to be an expert on voice spectrography lacked the required training, experience, or education). Moreover, expertise in one topic does not qualify a witness to testify about another topic. See, e.g., Engilis, 151 F.4th at 1050–54 (affirming exclusion of oncologist's opinion on specific causation because the oncologist failed to follow the differential etiology methodology his report purported to employ and failed to reliably rule out obesity as a potential cause of plaintiff's cancer); Brainchild Surgical Devices, LLC v. CPA Glob. Ltd., 144 F.4th 238, 254 (4th Cir. 2025) (affirming exclusion of expert with experience in international business and contracts to opine on patent renewal services where the expert lacked training or experience with patent renewal services); Kadel v. Folwell, 100 F.4th 122, 158 (4th Cir. 2025) (en banc) (affirming exclusion of medical doctors' testimony where doctors failed to demonstrate expertise in treating the medical condition at issue in the case), vacated on other grounds by Folwell v. Kadel, 145 S. Ct. 2838 (2025) (mem.); Sardis, 10 F.4th at 288–90, 295 (affirming exclusion of testimony about an industry standard not sufficiently related to the product at issue and excluding testimony that contradicts standards imposed by governing law); Zellers v. NexTech Ne., LLC, 533 F. App'x 192, 197 (4th Cir. 2013) (per curiam) (unpublished) (affirming exclusion of neurologist's testimony about the toxicity of certain chemicals used for refrigeration because the neurologist had no training in toxicology); Cooper, 259 F.3d at 200–04 (affirming exclusion of medical doctor's testimony where the medical doctor based an opinion on a medical device without conducting tests or studying the medical device); Ancho v. Pentek Corp., 157 F.3d 512, 519 (7th Cir. 1998) (affirming exclusion of testimony when the expert failed to visit the site of the accident or otherwise familiarize himself with the specific details of the accident at issue).

To be relevant, the proposed expert testimony must be helpful to the trier of fact concerning the evidence or a fact at issue in the case. See Fed. R. Evid. 702(a); Daubert, 509 U.S. at 591–92; United States v. Lespier, 725 F.3d 437, 449 (4th Cir. 2013); Kopf v. Skyrm, 993 F.2d 374, 377 (4th Cir. 1993); Persinger v. Norfolk & W. Ry., 920 F.2d 1185, 1188 (4th Cir. 1990); Scott v. Sears, Roebuck & Co., 789 F.2d 1052, 1055 (4th Cir. 1986). To be helpful, the proposed expert testimony must fit the facts of the case. See Fed. R. Evid. 702; Silicon Knights, Inc., 2011 WL 6748518, at *6–17. “Fit is not always obvious, and scientific validity for one purpose is not necessarily scientific validity for other, unrelated purposes.” Daubert, 509 U.S. at 591 (cleaned up). To be helpful to the trier of fact, the proposed expert testimony must be outside the common knowledge or function of the factfinder. See, e.g., Lespier, 725 F.3d at 449 (affirming exclusion of expert testimony on how sleep deprivation affects the reliability of an eye witness to a crime); Persinger, 920 F.2d at 1188 (affirming exclusion of expert testimony about the weight an individual could safely lift based on an easily-applied industry formula); Gladhill, 743 F.2d at 1052 (affirming decision that a police officer who had investigated 600 car accidents and arrived at the car accident scene immediately after the car accident was qualified to opine on the cause of the car accident based on his review of the car accident scene); cf. United States v. Hill, 749 F.3d 1250, 1260 (10th Cir. 2014) (holding that an expert witness cannot testify about whether another witness is credible); Nimely v. City of New York, 414 F.3d 381, 398 (2d Cir. 2005) (same).

“[T]he test of reliability is flexible and the law grants a district court” discretion when it decides reliability. United States v. Wilson, 484 F.3d 267, 274 (4th Cir. 2007) (cleaned up); see Kumho Tire Co., 526 U.S. at 141–42; Belville v. Ford Motor Co., 919 F.3d 224, 233 (4th Cir. 2019). Reliability focuses on the fit between the expert opinion and the facts of the case. There is not a fit when a large analytical gap exists between the facts of the case and the opinion. See, e.g., Joiner, 522 U.S. at 146–47 (affirming exclusion of testimony where the expert's opinion was based on irrelevant testing on animals unrelated to the case at issue); United States v. Hudak, 156 F.4th 405, 409–10 (4th Cir. 2025) (affirming exclusion of expert psychologist's testimony where expert opined that mental illness caused defendant's offense conduct but the psychologists report “included almost no facts about the period of time in which the conduct occurred”); Engilis, 151 F.4th at 1050–54 (affirming exclusion of oncologist's opinion on specific causation because the oncologist failed to follow the differential etiology methodology his report purported to employ and failed to reliably rule out obesity as a potential cause of plaintiff's cancer); In re Lipitor (Atorvastatin Calcium) Mktg., Sales Pracs. & Prods. Liab. Litig., 892 F.3d 624, 634–35, 644 (4th Cir. 2018) (affirming exclusion of testimony when the expert's testing contradicted his opinion); Nease v. Ford Motor Co., 848 F.3d 219, 232–33 (4th Cir. 2017) (affirming exclusion of testimony when expert on vehicle safety failed to test his own hypothesis); Cooper, 259 F.3d at 200–01 (affirming exclusion of testimony on what caused a medical injury when the expert's testing did not provide evidence of causation); Silicon Knights, Inc., 2011 WL 6748518, at *6–17 (excluding expert on damages where the opinions did not fit the facts of the case). Rule 702 does not permit or require “a district court to admit opinion evidence that is connected to existing data only by the ipse dixit of the expert.” Joiner, 522 U.S. at 146; see Small v. WellDyne, Inc., 927 F.3d 169, 177 (4th Cir. 2019) (“Without testing, supporting literature in the pertinent field, peer reviewed publications[,] or some basis to assess the level of reliability, expert opinion testimony can easily, but improperly, devolve into nothing more than proclaiming an opinion is true ‘because I say so.’ ”); In re Roundup Prods. Liab. Litig., MDL No. 2741, 2023 WL 7928751, at *2–6 (N.D. Cal. Nov. 15, 2023) (unpublished) (“For an expert to express an opinion that Roundup cause[d] [Non-Hodgkins Lymphoma], that expert must have engaged with the relevant literature enough to assess whether a study is credible, to explain why [he] relied on one study more than another, and to articulate how [he] reached [his] conclusion in the face of conflicting evidence. [The expert in this case] did not do that, so his general causation opinion is excluded.”), aff'd sub nom. Engilis, 151 F.4th 1040.

In determining “whether proffered testimony is sufficiently reliable, the court has broad latitude to consider whatever factors bearing on validity that the court finds to be useful; the particular factors will depend upon the unique circumstances of the expert testimony involved.” Westberry v. Gislaved Gummi AB, 178 F.3d 257, 261 & n.1 (4th Cir. 1999). Factors that may bear on the reliability of the expert's testimony include (1) whether a theory or technique can be (and has been) tested, (2) whether the theory or technique has been subjected to peer review and publication, (3) whether a technique has a high known or potential rate of error and whether there are standards controlling its application, and (4) whether the theory or technique enjoys general acceptance within the relevant community. See Kumho Tire Co., 526 U.S. at 149–50; Daubert, 509 U.S. at 593–94; see, e.g., Engilis, 151 F.4th at 1050–54 (affirming exclusion of oncologist's opinion on specific causation because the oncologist failed to follow the differential etiology methodology his report purported to employ and failed to reliably rule out obesity as a potential cause of plaintiff's cancer); Sardis, 10 F.4th at 288–90 (holding testimony about product safety unreliable when expert did not test the product); McKiver v. Murphy-Brown, LLC, 980 F.3d 937, 960 (4th Cir. 2020) (holding that a witness's method for analyzing the origin of swine fecal material was widely used and applied reliably enough to be admitted despite not being subject to peer review); In re Lipitor, 892 F.3d at 644–45 (holding that medical doctor's testimony that Lipitor caused certain diseases was excludable for not factoring in other risk factors, such as age, body mass index, and family history); Baxter v. Comm'r of IRS, 910 F.3d 150, 157–58 (4th Cir. 2018) (holding that mere disagreement with an expert's otherwise reliable economic methodology is not grounds for exclusion); United States v. Crisp, 324 F.3d 261, 265–70 (4th Cir. 2003) (holding that expert fingerprint analysis was admissible despite defendant's objections to its general scientific accuracy). “Result-driven analysis, or cherry-picking, undermines principles of the scientific method and is a quintessential example of applying methodologies (valid or otherwise) in an unreliable fashion.” In re Lipitor, 892 F.3d at 634; see E.E.O.C. v. Freeman, 778 F.3d 463, 468–70 (4th Cir. 2015) (Agee, J., concurring) (collecting cases).

A.

Plaintiffs move to preclude defendants' epidemiology expert Alexander from discussing the incidence of certain cancers in North Carolina. See [D.E. 288]. Defendants retained Alexander “to conduct a state-of-the-epidemiologic science review of per- and polyfluoroalkyl substances [(“PFAS”)].” [D.E. 289-2] 7. Alexander is the owner and principal epidemiologist at an epidemiology consulting firm. See id. Alexander supplemented his original report. See [D.E. 289-4].

One section of Alexander's initial report contains statistics about the incidence of certain cancers in certain North Carolina counties. See [D.E. 289-2] 31–37. Specifically, Alexander compared the incidence of certain cancers among residents of Bladen, Brunswick, Cumberland, New Hanover, and Pender Counties, with those of Columbus, Harnett, Johnston, Sampson, and Robeson Counties, and those of Cherokee, Catawbe, Gulliford, Gaston, and Franklin Counties. See, e.g., id. at 31. Alexander opines that:

Based on validated North Carolina State Cancer Profile data, the reported rates of cancer in the counties allegedly impacted by PFCs originating from the Fayetteville Works facility are not increased compared to rates of cancer in the U.S. general population, the state of North Carolina, adjacent or neighboring counties without exposure to PFCs, including GenX compounds or long-chain PFASs, or descriptively matched counties without exposure to PFCs, including GenX compounds or long-chain PFASs. Thus, there is no epidemiologic basis that exposure to PFCs, including exposures to GenX compounds or relevant long-chain PFASs, would be meaningful contributors to cancer risk in the counties allegedly impacted by these chemicals from the Fayetteville Works facility. Furthermore, there is no analytical epidemiologic evidence to support an association between exposure to GenX compounds and any type of human disease.

Id. at 8. Plaintiffs argue that cancer incidence data has “little if any probative value” because the county-level data cannot demonstrate causation and will only suggest an improper causal inference to the jury. [D.E. 289] 5; see id. at 5–6. Defendants acknowledge the impropriety of inferring causation from the cancer incidence statistics alone and respond that the county-level data validates Alexander's other opinions. See [D.E. 304] 3–4.

The court agrees with the parties that it is improper for Alexander to suggest or opine that the county-level data support a causal inference. The relevant portion of Alexander's report offers an ecological study. An ecological study “obtain[s] and compare[s] overall rates of disease or death” among two groups. See Federal Judicial Center, Reference Manual on Scientific Evidence 912 (4th ed. 2025). The objective is to identify some group-level difference that might explain differences in their risk of disease. See id. Ecological studies “rarely provide causal answers.” Id. As Alexander testified during his deposition, the cancer incidence data does not demonstrate causation. See, e.g., [D.E. 289-1] 9; cf. [D.E. 304] 3 (“Alexander does not rely on the North Carolina State Cancer Profile data as a basis for his general causation opinion.”). Alexander's county-level data cannot validate his analytical opinions (i.e., that the available evidence does not support general causation) because the county-level data has no bearing on causation. Cancer rates may have gone up or down in the relevant counties for myriad reasons. Thus, the court grants plaintiffs' motion to exclude Alexander's cancer incidence opinion to show causation and need not address the parties' arguments about Alexander's method for picking comparison counties.

B.

Defendants move to exclude the report and testimony of plaintiffs' expert DeWitt. See [D.E. 298]. DeWitt is a toxicologist who holds a bachelor's degree in biology and environmental science from Michigan State University and a Ph.D. in environmental affairs and neural science. See [D.E. 165-1] 67. DeWitt is a professor of pharmacology and toxicology at East Carolina University and an adjunct professor at North Carolina State University. See id. DeWitt's primary opinion, offered in her initial report, is that “the weight of the toxicological evidence, with confirmation from certain epidemiological evidence, that exposure to PFAS—including those found in [p]laintiffs' wells and at their properties—poses a hazard to human health.” Id. at 15. In related cases, the court has excluded certain of DeWitt's opinions because DeWitt offered the unsupported opinion that “any non-zero level of PFAS in drinking water is unsafe and hazardous to human and environmental health.” Nix v. Chemours Co. FC, 805 F. Supp. 3d 626, 656 (E.D.N.C. 2025). In light of that defect, the court also excluded DeWitt's opinions as unhelpful to the jury. See id. at 656–57.

In this case, DeWitt offered essentially the same opinion in her initial report as she offered in Nix. See, e.g., 805 F. Supp. 3d 626 at 653–55; [D.E. 165-1] 15 (“It is my opinion, based on the weight of the toxicological evidence, with confirmation from certain epidemiological evidence, that exposure to PFAS—including those found in [p]laintiffs' wells and at their properties—poses a hazard to human health.”). Plaintiffs now state, however, that DeWitt will not testify that any plaintiff suffers a physical injury that is, or could be, caused by exposure to PFAS or “that any [p]laintiff is at a particular risk of an identified disease or condition.” [D.E. 301] 3. Plaintiffs also state that DeWitt “will not testify that there is no safe level of exposure to the PFAS released from Fayetteville Works or that any non-zero level of PFAS is unsafe.” Id. at 5. Instead, plaintiffs proffer DeWitt's report and testimony on the “general traits of PFAS compounds,” the “state of the science” of PFAS toxicology, and to counter the opinions of defendants' experts Finley and Alexander. Id. at 2–3. Plaintiffs argue that DeWitt's opinions will contextualize the alleged reasonableness of plaintiffs' claims for damages. See id. at 5–6.

In light of plaintiffs' concessions, DeWitt's proffered testimony may be helpful to the jury's consideration of plaintiffs' damages claims. See Daubert, 509 U.S. at 591 (“Fit is not always obvious, and scientific validity for one purpose is not necessarily scientific validity for other, unrelated purposes.” (cleaned up)); Parris v. 3M Co., No. 4:21-CV-40, 2026 WL 791605, at *4–6 (N.D. Ga. Mar. 20, 2026) (unpublished) (agreeing with the court's analysis in Nix concerning DeWitt's opinions about safe and unsafe PFAS exposure levels, but permitting DeWitt to opine regarding “identifying potential health risks associated with PFAS exposure in the scientific literature”). But DeWitt cannot speculate on general causation or offer causation testimony under the guise of discussing the “general traits of PFAS compounds,” the “state of the science” of PFAS toxicology, or rebutting the opinions of defendants' experts. [D.E. 301] 3; see Fed. R. Evid. 702(d); Fed. R. Evid. 702 advisory committee's note to 2023 amendment (“Judicial gatekeeping is essential because just as jurors may be unable, due to lack of specialized knowledge, to evaluate meaningfully the reliability of scientific and other methods underlying expert opinion, jurors may also lack the specialized knowledge to determine whether the conclusions of an expert go beyond what the expert's basis and methodology may reliably support.”).

The court rejects defendants' argument that DeWitt's opinions are unreliable because she did not conduct a qualitative risk assessment. See [D.E. 299] 5–6. DeWitt need not conduct such an assessment to offer the testimony on which plaintiff's now proffer her. The court agrees with defendants, however, that DeWitt may not offer an opinion about general causation or alleged unsafe levels of PFAS.

Defendants also argue that DeWitt's comparison of regulatory standards for PFOA and PFOS to the compounds that plaintiffs seek to recover for in this case “distorts” the import of the regulatory guidelines, rendering her comparison unhelpful to the jury. See id. at 7–10. Plaintiffs respond that defendants' arguments about the applicable regulatory standards do not render DeWitt's comparison inadmissible. See [D.E. 301] 8–12.

The court rejects defendants' arguments. Defendants first argue that the EPA's intent to vacate certain regulatory standards for PFAS chemicals demonstrates that DeWitt should not have relied upon those standards. See [D.E. 299] 8. But the EPA's motion for partial vacatur filed in the D.C. Circuit relies on an alleged legal error in the rulemaking process. See [D.E. 299-4]. The EPA rulemaking process has no bearing on the way DeWitt used the regulatory standards. Moreover, the D.C. Circuit denied the motion for partial vacatur on which defendants rely, and the case otherwise appears to be proceeding in due course. See Order on Mot. for Partial Vacatur, Am. Water Works Ass'n v. EPA, No. 24-1188 (D.C. Cir. Jan. 21, 2026) (per curiam), Doc. #2155270; cf. [D.E. 327] 2–3. Thus, the court disagrees with defendants that DeWitt erred by considering regulatory standards that are in effect.

Next, defendants argue that maximum contaminant levels (“MCLs”), a regulatory standard on which DeWitt relies, “set a level below which exposure to PFAS in drinking water is deemed safe,” rendering DeWitt's reliance on them a “non sequitur.” [D.E. 299] 9. The parties' dispute about how much weight to place on the MCLs (which do not strictly apply to private water users like plaintiffs) is a question “best settled by a battle of the experts before the fact finder, not by judicial fiat.” Sommerville, 149 F.4th at 424 (citation omitted). Thus, the court rejects this argument. Defendants also contend that DeWitt's reliance on the regulatory standards is not useful to determine whether PFAS exposure at any particular moment is harmful, and that the regulatory standards are irrelevant because plaintiffs have abstained from consuming water contaminated with PFAS. See [D.E. 299] 9–10. Both arguments fail in light of plaintiffs' concession that they will not offer DeWitt's testimony about personal injury or causation. See [D.E. 301] 11.

Defendants also argue that DeWitt's opinions are irrelevant because this is not a personal injury case. See [D.E. 299] 11–12. The court agrees that this is not a personal injury case. As the Parris court recognized, however, DeWitt's testimony may contextualize plaintiffs' decisions about PFAS without impermissibly opining about general causation. See 2026 WL 791605, at *5. The court will ensure that DeWitt does not so impermissibly testify. Cf. Nix, 805 F. Supp. 3d at 656. Thus, the court denies defendants' motion to exclude DeWitt's testimony subject to the limitations on that testimony imposed by this order and plaintiffs' representations in their brief.

C.

Defendants move to exclude or limit the expert opinions of plaintiffs' expert Adam Domanski, Ph.D. See [D.E. 291]. Domanski is an economist who evaluated the effect of “contamination from the Chemours Fayetteville Works Plant” on residential property values. [D.E. 293-2] 6–7. Earlier in the case, defendants moved to exclude Domanski's report and testimony. See [D.E. 188]. Defendants argued that Domanski did not properly apply the difference-in-difference econometric methodology, subjectively designed his model, cherry-picked the data he used, produced a model with statistically insignificant findings, and offered unfounded opinions that did not fit the case. See Dew v. E.I. du Pont de Nemours & Co., No. 5:18-CV-73, 2024 WL 4349883, at *5 (E.D.N.C. Sept. 30, 2024) (unpublished). The court denied the motion, rejected defendants' arguments, and explained that Domanski's report and testimony satisfied Rule 702's requirements. See id. at *4–8.

Domanski supplemented his initial report to update his model with the “most recent data.” [D.E. 293-3] 4; [D.E. 302-2] 3; see Domanski Suppl. Report [D.E. 293-1] 4–5. Domanski's model otherwise remains the same model that defendants contested in their earlier motion. See Domanski Decl. [D.E. 302-1] ¶ 11. Domanski's supplemental report contains the following opinions: (1) “[r]esidential properties surrounding the Chemours Fayetteville Works Plant have diminished value due to environmental contamination,” (2) plaintiffs Richard and Patsy Davis have lost $141,988 in residential property value, Annie and John Stevens have lost $64,083 in residential property value, Allison Pini has lost $27,502 in residential property value, and Sandra Riggins Branch has lost $46,838 in residential property value, and (3) “[t]he Chemours Company, DuPont de Nemours and Company, and Corteva Inc./EIDP Inc are each financially viable companies with current assets exceeding $3 billion, $6.3 billion, and $17.3 billion, respectively.” Domanski Suppl. Report 4–5.

Defendants argue that Domanski's second opinion is unreliable and that, without the second opinion, Domanski's first opinion cannot assist the trier of fact. See [D.E. 293] 2, 7–15. Specifically, defendants contend that the dollar-figure estimates Domanski calculated for the trial plaintiffs' properties are unreliable because (1) Domanski's estimates rely on three post-regression calculations that defendants could not replicate, (2) Domanski did not statistically validate the dollar-figure estimates, which do not account for the actual PFAS contamination of individual properties, and (3) Domanski's three post-regression calculations are not backed by peer-reviewed literature. See id. at 7–14.

The court rejects defendants' arguments about Domanski's post-regression calculations. Domanski explained his methodology, including the post-regression calculations, in detail in his initial report and during his deposition. See [D.E. 293-2] 7–11; [D.E. 293-3] 5–8, 13–20. Defendants' failure to replicate Domanski's calculation results from rounding. See Domanski Decl. ¶ 19. That Domanski rounded certain values in his report to the nearest tenth decimal does not render the dollar-figure estimates unreliable. As for defendants' argument about statistical validation, defendants' desire to impose a validation requirement (i.e., that Domanski calculate confidence intervals concerning the dollar-figure estimates) is not a proper basis for excluding an expert's report and testimony. See Sommerville, 149 F.4th at 424 (“Excluding [the expert] for failing to ‘validate’ his data was a glaring abuse of discretion.”). Moreover, Domanski's model provides standard errors and an R-squared. From standard errors, confidence intervals may be derived. See Domanski Decl. ¶ 13. The R-squared measures the amount of variation in the data that the model can explain. See id. ¶¶ 16–17. As the court explained when it rejected defendants' similar argument about Domanski's initial report, “[d]efendants can scrutinize Dr. Domanski's specific methodological choices on cross examination.” Dew, 2024 WL 4349883, at *5.

As for defendants' argument about peer review, the difference-in-difference econometric model has been peer reviewed and approved as a reliable econometric method. See id. Domanski derived the dollar-figure estimates from the difference-in-difference model by converting the regression coefficients to dollar-figure estimates using rudimentary mathematics. See Domanski Decl. ¶ 12. Using mathematics to convert regression coefficients to dollar-figure estimates is not the type of issue on which peer review is helpful when determining reliability. See, e.g., Kumho Tire Co., 526 U.S. at 150–51. Thus, the court rejects defendants' arguments.

As for defendants' argument that Domanski's model did not account for PFAS contamination on individual properties and did not use updated property appraisals, “[w]here an expert witness explains why he considered certain variables and did not consider others in his econometric analyses, cross examination provides the best means for settling disputes about the intricacies of econometric analyses.” Dew, 2024 WL 4349883, at *5; see id. at *7–8 (rejecting similar argument); SMD Software, Inc. v. EMove, Inc., 945 F. Supp. 2d 628, 642 (E.D.N.C. 2013). Domanski explained his decisions to consider certain variables at the cost of other variables. See [D.E. 293-3] 10–11, 18–19. Those decisions do not render his methodology unreliable. See Sommerville, 149 F.4th at 423 (holding that a district court abused its discretion by ignoring or discounting expert's explanations for making certain assumptions); Dew, 2024 WL 4349883, at *8 (describing similar argument as “prime fodder for cross examination, not exclusion under Rule 702”). Defendants also cite evidence that the Cumberland County Regular Board of Equalization and Review (the “Board”) rejected some residents' claims for reduced property tax assessments because of PFAS-contamination on their properties. See [D.E. 389] 1–3; [D.E. 389-1] 2–17. The Board's disagreement with Domanski does not render Domanski's opinion unreliable. Defendants are free to cross-examine Domanski about his disagreement with the Board's decisions, including decisions discussed in defendants' motion to supplement [D.E. 391]. See Dew, 2024 WL 4349883, at *8; cf. [D.E. 394] 7 (acknowledging defendants' ability to cross-examine Domanski about the Board's December 2025 meeting minutes). Thus, the court rejects this argument. Because the court rejects defendants' arguments that Domanski's second opinion is unreliable, the court also rejects defendants' request to exclude Domanski's first opinion.

Defendants argue that Domanski's third opinion should be limited to the named defendants (i.e., that the opinion should not include the finances of nonparties Corteva, Inc. (“Corteva”) and DuPont de Nemours, Inc. (“new DuPont”)). See [D.E. 293] 16–17. Defendants argue that evidence of a nonparty's finances is irrelevant. See id. The Supreme Court of North Carolina has held that North Carolina courts have personal jurisdiction over Corteva and new DuPont based on agreements under which Corteva and new DuPont assumed the PFAS-related liabilities of E.I DuPont de Nemours and Company. See State ex rel. Stein v. E.I. du Pont de Nemours & Co., 382 N.C. 549, 562–65, 879 S.E.2d 537, 547–49 (2022). Plaintiffs cite new DuPont's financial statements, which state that new DuPont, Corteva, E.I. Du Pont De Nemours and Company, and Chemours “have agreed to share certain costs associated with potential future liabilities related to alleged historical releases of certain PFAS out of pre-July 1, 2015 conduct” and that some legal matters (presumably this one included) “are pending against Chemours and/or Corteva/EIDP in which [new DuPont] is not named․ Regardless of whether [new DuPont] is named, the costs of litigation and future liabilities, if any, in these matters, are or may be eligible PFAS costs under” the agreements between the companies. [D.E. 302-6] 123, 127; cf. id. at 125 (“With the exception of the fraudulent conveyance claims, which are excluded from the MOU, legal fees, expenses, costs, and any potential liabilities for eligible PFAS costs presented by the following matters will be shared in accordance with the MOU between Chemours, EIDP, Corteva and DuPont.”).

Defendants' motion concerning Domanski's third opinion is, in substance, a motion in limine about evidence of the nonparties' financial viability. That evidence is not clearly inadmissible on all possible grounds. Cf. McKiver, 980 F.3d at 973–74 (affirming district court's decision to admit certain financial evidence over a Rule 403 objection because North Carolina nuisance law allowed jury to consider the evidence and party argued it could not afford remediation). Thus, the court denies without prejudice defendants' motion to exclude Domanski's third opinion.

D.

Defendants move to exclude plaintiffs' expert Duckworth. See [D.E. 294]. Duckworth is a professor of soil biogeochemistry at North Carolina State University. See [D.E. 162-1] 16. Duckworth opines about plants containing PFAS. Specifically, Duckworth opines that (1) “Fayetteville Works PFAS can be taken up through the root systems and transported internally into arial tissues of plants” which “may result in Fayetteville Works PFAS concentrating in edible portions of food plants,” (2) “Fayetteville Works PFAS have been found in produce grown in a residential garden located approximately two miles from the facility” and “reflect those found in groundwater and soil at the location where the produce was grown,” (3) “[g]iven the documented presence of Fayetteville Works PFAS in groundwater and soil at [p]laintiffs' properties (‘Bellwether Properties’), produce grown at the Bellwether Properties may accumulate and would pose a significant risk of containing elevated concentrations of Fayetteville Works PFAS,” and (4) “[c]onsumption of food containing Fayetteville Works PFAS would contribute to human exposure to Fayetteville Works PFAS.” Id. at 4. Defendants challenge Duckworth's third and fourth opinions. See [D.E. 295] 2–3.

Defendants argue that Duckworth's third opinion is based on insufficient facts and data because he tested produce from the John and Annie Stevens' property but opines about all of trial plaintiffs' properties. See id. at 2–3, 6–9. But plaintiffs do not offer Duckworth to opine about contamination levels. Plaintiffs offer Duckworth's testimony to show the alleged reasonableness of plaintiffs' decisions to abstain from growing and eating produce. See [D.E. 300] 6; cf. [D.E. 162-1] 10 (“Consumption of home and locally grown foods is thus an additional route of PFAS exposure for this community.”) Duckworth has a sufficient basis for his third opinion, including academic articles investigating PFAS uptake by plants, his own sampling of the Stevens' property, and scientific principles. See [D.E. 162-1] 4–10. Duckworth does not opine about specific contamination values on the other trial plaintiffs' properties, which would require additional factual support. Cf. Nix, 805 F. Supp. 3d at 647–48 (rejecting challenge to expert's report where expert's opinions were offered for purpose that did not require expert to establish specific contamination values from reliable testing). Thus, the court rejects defendants' arguments about Duckworth's third opinion.

Next, defendants argue that Duckworth's fourth opinion will not help the trier of fact because it is commonsense that eating produce containing PFAS increases exposure to PFAS. See [D.E. 295] 9–11. Although part of Duckworth's fourth opinion (i.e., that eating produce containing PFAS increases exposure to PFAS) is commonsense, it does not render the opinion unhelpful to the jury given the rest of Duckworth's fourth opinion, which includes matters outside the jury's commonsense. See [D.E. 162-1] 10 (conceptualizing PFAS exposure from produce using comparison to different quantities of water). Defendants also argue that no expert could testify that such produce exposure is “harmful to the [p]laintiffs,” so the exposure evidence “cannot support [p]laintiffs' claims for loss of use and enjoyment of their properties, much less negligence damages.” [D.E. 295] 10. Defendants, however, do not cite authority under North Carolina law for the proposition that plaintiffs cannot recover on their claims unless the exposure to PFAS is harmful to plaintiffs' health. Cf. Dew, 2024 WL 4349883, at *14–15 (“A reasonable jury could find defendants liable for [plaintiff's] private nuisance claim.”). Thus, the court denies defendants' motion to exclude Duckworth's report and testimony.

E.

Defendants move to exclude plaintiffs' expert LaRosa. See [D.E. 296]. LaRosa is a senior technical leader at an engineering firm and leads the firm's emerging contaminants working group. See [D.E. 297-9] 2. LaRosa has 36 years of experience “performing assessment and remediation of environmental contaminants, drinking water source development and on site wastewater disposal.” Id. Plaintiffs offer LaRosa's report and testimony to “explain the costs of installing, operating, and maintaining a point of entry treatment (POET) system to remove Fayetteville Works PFAS from the household water at three of the five properties at issue.” [D.E. 305] 1. LaRosa's report estimates the costs of installing, operating, and maintaining a POET system over a 40-year timespan in net present value terms. See [D.E. 297-9] 2–7. LaRosa's report includes a range of costs depending on whether the systems require a booster pump and whether the granular activated carbon will need to be changed at quarterly or yearly increments. See id. at 5–7.

Defendants argue that LaRosa's cost calculations do not fit the facts of the case because LaRosa ignores that defendants offered plaintiffs water filtration systems and monitoring, and that plaintiffs' properties may be connected to public water in the future. See [D.E. 297] 4–7. Defendants' arguments are based on speculation about uncertain future decisions and plaintiffs' decisions to reject defendants' offers. Defendants' arguments that LaRosa's assumptions about the future may be proven wrong in hindsight and that defendants wish plaintiffs accepted their offers go to the weight, not the admissibility, of LaRosa's cost calculations. Cf. Dew v. E.I. du Pont de Nemours & Co., No. 5:18-CV-73, 2025 WL 1174727, at *10 (E.D.N.C. Mar. 31, 2025) (unpublished) (“North Carolina law does not preclude plaintiffs[ ] from seeking all damages related to a final water solution.”). Defendants also argue that LaRosa's calculations duplicate Domanski's opinions. But Domanski opines about the market value of the properties, while LaRosa's calculations concern the costs of the water treatment systems on the properties themselves. Compare [D.E. 302-1] ¶¶ 8–10, with [D.E. 297-9] 2.

Defendants also argue that LaRosa's methodology is unreliable because LaRosa stated that the total cost of treatment cannot be determined because the POET system might require a booster pump. See [D.E. 297] 7–9. LaRosa stated that the pump's necessity can be determined only after installing the system. Defendants do not explain why LaRosa's calculation of two figures, one accounting for the cost of the pump and one which does not, renders his calculations inadmissible. Similarly, LaRosa explained why he uses the level of “non-detect” as a goal in residential treatment systems. See [D.E. 305-2] 5–6; cf. Sommerville, 149 F.4th at 423. LaRosa's decision to use non-detect as a goal does not render his calculations unreliable. Thus, the court denies defendants' motion to exclude LaRosa's report and testimony.

II.

Plaintiffs move to exclude opinion one of Finley's supplemental report. See [D.E. 290]. The court's case management order required defendants to serve supplemental expert reports by March 27, 2026. See [D.E. 286] 2. Federal Rule of Civil Procedure 26(a)(2)(A) requires parties to “disclose to the other parties the identity of any [expert] witness.” Fed. R. Civ. P. 26(a)(2)(A). “[T]his disclosure must be accompanied by a written report ․ if the witness is one retained or specially employed to provide expert testimony ․” Fed. R. Civ. P. 26(a)(2)(B). The report must include “a complete statement of all opinions the witness will express and the basis and reasons for them.” Fed. R. Civ. P. 26(a)(2)(B)(i). Parties “must make these disclosures at the times and in the sequence that the court orders.” Fed. R. Civ. P. 26(a)(2)(D). A report that fails to include a complete statement of all opinions creates unfair surprise. See, e.g., Smith v. State Farm Fire & Cas. Co., 164 F.R.D. 49, 53–54 (S.D. W. Va. 1995).

Rule 26(e) requires a supplemental report when a party “learns that in some material respect the disclosure or response is incomplete or incorrect,” Fed. R. Civ. P. 26(e)(1)(A). But Rule 26(e) does not create a “right to produce information in a belated fashion,” EEOC v. Freeman, 961 F. Supp. 2d 783, 797 (D. Md. 2013) (citation omitted), aff'd in part, 778 F.3d 463 (4th Cir. 2015). Correcting an inadvertent error or completing a report with information that was not available by the initial disclosure deadline exemplifies proper supplementation. See id. at 797; Keener v. United States, 181 F.R.D. 639, 640 (D. Mont. 1998). Courts, however, distinguish “true supplementation ․ from gamesmanship.” Gallagher v. S. Source Packaging, LLC, 568 F. Supp. 2d 624, 631 (E.D.N.C. 2008) (citation omitted). And courts repeatedly reject attempts to provide “new and improved” expert opinions under the guise of supplementation. Id.; see Pierce v. N.C. State Bd. of Elections, No. 4:23-CV-193, 2024 WL 5170738, at *3 (E.D.N.C. Dec. 18, 2024) (unpublished); Solaia Tech. LLC v. ArvinMeritor, Inc., 361 F. Supp. 2d 797, 806–07 (N.D. Ill. 2005); Coles v. Perry, 217 F.R.D. 1, 3–4 (D.D.C. 2003). Thus, supplementation “does not cover failures of omission because the expert did an inadequate or incomplete preparation.” Akeva LLC v. Mizuno Corp., 212 F.R.D. 306, 310 (M.D.N.C. 2002).

Rule 37(c)(1) “give[s] teeth” to Rule 26's disclosure obligations. Vanderberg v. Petco Animal Supplies Stores, Inc., 906 F.3d 698, 702 (8th Cir. 2018). “If a party fails to provide information or identify a witness as required by Rule 26(a) or (e), the party is not allowed to use that information or witness to supply evidence ․ at a trial, unless the failure was substantially justified or is harmless.” Fed. R. Civ. P. 37(c)(1); see S. States Rack & Fixture v. Sherwin-Williams Co., 318 F.3d 592, 596 (4th Cir. 2003); Ali v. Worldwide Language Res., LLC, 686 F. Supp. 3d 430, 444–45 (E.D.N.C. 2023). “The party failing to disclose information bears the burden of establishing that the nondisclosure was substantially justified or was harmless.” Bresler v. Wilmington Tr. Co., 855 F.3d 178, 190 (4th Cir. 2017). The court must consider “(1) the surprise to the party against whom the evidence would be offered; (2) the ability of that party to cure the surprise; (3) the extent to which allowing the evidence would disrupt the trial; (4) the importance of the evidence; and (5) the nondisclosing party's explanation for its failure to disclose the evidence.” S. States, 318 F.3d at 597; see Pierce, 2024 WL 5170738, at *4; Ali, 686 F. Supp. 3d at 445. The first four factors “relate mainly to the harmlessness exception, while the remaining factor—explanation for the nondisclosure—relates primarily to the substantial justification exception.” S. States, 318 F.3d at 597; see Bresler, 855 F.3d at 190.

Defendants designated Finley as an expert to opine about the effect of PFAS exposure on developing disease. See Dew, 2024 WL 4349883, at *9–12. In his initial report, Finley “applie[d] a risk assessment methodology to determine whether hexafluoropropylene oxide dimer acid (GenX), perfluoro-2-methoxyaacetic acid (PFMOAA), perfluorooctanoic acid (PFOA), or perfluorooctane sulfonic acid (PFOS) pose a health risk.” Id. at *9 (quotations omitted). Opinion one of Finley's supplemental report includes the following substances that he did not discuss in his original report: PFMOBA/PEPA, PFMOPrA/PMPA, PFO3OA, and PFPrA. See [D.E. 292-7] 14. Finley “considered any PFAS congener for which there is an established EPA oral RfD [(reference dose)], or a provisional chronic oral toxicity value (PCOTV) derived” from a 2026 research paper that Finley coauthored. Id. at 7; see [D.E. 292-9].

Plaintiffs argue that Finley's opinion about PFPrA is an improper supplement because, in June 2023, the EPA derived an oral reference dose human health toxicity value for PFPrA. See [D.E. 292] 9; [D.E. 292-4] 2–3; cf. [D.E. 292-7] 13. Finley's initial report is dated July 12, 2023. See generally [D.E. 292-6]. For the remaining substances, plaintiffs argue that Finley could have included them in his original report because, though he cites the 2026 research paper, it relies on studies that predate Finley's initial report. See [D.E. 292] 9–10.

The court agrees with plaintiffs that Finley could have included PFPrA in his initial report based on the EPA's June 2023 publication but did not do so. Thus, the court grants plaintiffs' motion to exclude Finley's supplemental opinion one concerning PFPrA. See, e.g., Pierce, 2024 WL 5170738, at *3; Akeva, 212 F.R.D. at 310. Nonetheless, Finley's supplemental opinion one properly accounted for new developments about the remaining substances. Although the 2026 research paper relies on prior studies, the paper derived the PCOTVs from raw data from those studies. See [D.E. 292-9] 3–4. It did not simply restate or repackage data from the prior studies to make Finley's omission the result of “an inadequate or incomplete preparation” of the initial report. Akeva, 212 F.R.D. at 310. Thus, the court denies plaintiffs' motion to exclude Finley's supplemental opinion one concerning PFMOBA/PEPA, PFMOPrA/PMPA, and PFO3OA. Accordingly, the court grants in part and denies in part plaintiffs' motion to exclude Finley's report and testimony.

III.

In sum, the court GRANTS plaintiffs' motion to exclude Alexander's opinion about county-level cancer incidence data [D.E. 288] and GRANTS IN PART and DENIES IN PART plaintiffs' motion to exclude Finley [D.E. 290]. The court GRANTS defendants' motion to supplement the record [D.E. 391], DENIES defendants' motions to exclude Domanski [D.E. 291], Duckworth [D.E. 294], LaRosa [D.E. 296], and DeWitt [D.E. 298], and DENIES defendants' motion filed in error [D.E. 388].

SO ORDERED. This 2 day of July, 2026.

JAMES C. DEVER III United States District Judge