Marpe v. Tonoga, Inc.: Limiting Frye Hearings and Clarifying Expert Causation Standards in New York PFOA Toxic-Tort Litigation

I. Introduction

The Appellate Division, Third Department’s decision in Marpe v. Tonoga, Inc., 2025 NY Slip Op 07053 (Dec. 18, 2025), is a significant procedural and evidentiary ruling in New York toxic-tort law, and particularly in the burgeoning litigation over perfluorooctanoic acid (PFOA) contamination in Hoosick Falls and surrounding areas.

The case addresses whether a trial court may require a full-blown evidentiary hearing (a Frye hearing) on the admissibility of plaintiffs’ expert testimony, where the experts’ methodologies are already well established in the scientific and legal community and where their submissions facially satisfy the causation requirements articulated in Parker v. Mobil Oil Corp., 7 NY3d 434 (2006). The Third Department holds that, under such circumstances, ordering a hearing is an abuse of discretion and that the defendant’s motions to preclude the experts and obtain summary judgment should have been denied outright.

In doing so, the court:

• Reinforces the narrow and focused role of the Frye test in New York.
• Clarifies how Parker’s foundational requirements for toxic-tort causation should be applied at the motion stage.
• Formally recognizes that the methodologies used by key PFOA experts (epidemiology, differential diagnosis, and medical monitoring assessment) are not “novel” and have already been accepted in other courts.
• Signals to trial courts that routine orders for evidentiary hearings in similar toxic-tort contexts may improperly expand judicial gatekeeping and delay litigation.

II. Factual and Procedural Background

A. The Underlying Litigation

These consolidated appeals arise from four related actions involving alleged PFOA contamination in municipal water supplies and private wells in the Village of Hoosick Falls and the Towns of Hoosick and Petersburgh in Rensselaer County, New York. The contamination allegedly occurred over decades (1954–2016) and has been the subject of extensive civil litigation and regulatory action, including designation of affected sites as federal Superfund locations.

The three named plaintiffs in the captioned actions—Emily Marpe, Beverly Waitekus, and Macy Lindsey (collectively “plaintiffs”)—allege that:

• Defendant Saint-Gobain Performance Plastics Corp. (“Saint-Gobain”) released PFOA into the air and soil from its manufacturing plant between 1996 and 2003.
• This facility is now a designated Superfund site.
• The releases contaminated their drinking water, resulting in exposure to elevated levels of PFOA.
• As a result of this exposure, they developed various thyroid diseases.

Plaintiffs settled with all other defendants, leaving Saint-Gobain as the sole remaining defendant in these actions.

B. The Motions Below

Saint-Gobain moved in each action:

1. To preclude the testimony of three key expert witnesses proffered by plaintiffs, and
2. For summary judgment, premised on the exclusion of that expert testimony.

The challenged experts were:

1. Dr. David Savitz – plaintiffs’ general causation expert, an epidemiologist opining on whether PFOA exposure is capable of causing thyroid disease in humans.
2. Dr. Manijeh Berenji – plaintiffs’ specific causation expert, who used a differential diagnosis to conclude that PFOA exposure was a significant factor in causing each plaintiff’s thyroid condition.
3. Dr. Alan Ducatman – plaintiffs’ expert on medical monitoring, opining on plaintiffs’ future need for medical surveillance due to their PFOA exposure.

Saint-Gobain argued that:

• The experts’ testimony constituted novel scientific evidence requiring scrutiny under Frye v. United States, 293 F 1013 (DC Cir 1923), and
• The experts did not satisfy Parker’s foundational requirements for causation in toxic-tort cases—particularly with respect to general and specific causation.

Supreme Court (Silverman, J.) did not immediately decide the motions. Instead, it ordered a joint evidentiary hearing to determine the admissibility of plaintiffs’ expert testimony. Plaintiffs appealed, contending that ordering such a hearing was an abuse of discretion in light of the record and existing precedent.

C. Appealability

An order merely granting a hearing to assist in deciding a motion is generally not appealable as of right (CPLR 5701[a][2][v]). The Third Department acknowledged this line of authority, citing:

• Matter of Chain Trust, 220 AD3d 770 (2d Dept 2023)
• Matter of Civil Serv. Empls. Assn., Local 1000 v Evans, 92 AD2d 669 (3d Dept 1983)
• Contra-leaning examples such as Parker v Crown Equip. Corp., 39 AD3d 347 (1st Dept 2007), and Stowell v Berstyn, 26 AD2d 828 (2d Dept 1966)

However, the court exercised its authority under CPLR 5701(c) to treat the notices of appeal as applications for permission to appeal, and granted them, citing Mahoney v Staffa, 168 AD2d 809 (3d Dept 1990). Thus, the Third Department reached the merits.

III. Summary of the Opinion

Justice Ceresia, writing for a unanimous panel, reversed Supreme Court’s order and held:

1. No Frye hearing was warranted.
   • Saint-Gobain’s objections largely challenged the reliability of the experts’ conclusions, not the novelty or general acceptance of their methodologies.
   • The methodologies used by all three experts (epidemiology for general causation, differential diagnosis for specific causation, and medical monitoring assessment) are well-established and have been accepted in prior New York and federal PFOA litigation, including Burdick v Tonoga, Inc. and Baker v Saint-Gobain Performance Plastics Corp.
   • Under New York law, absent a truly “novel or experimental” scientific theory, a Frye hearing is generally unwarranted.
2. The experts’ submissions satisfied Parker’s causation framework.
   • General causation: Dr. Savitz’s report went beyond showing an association and provided a reasoned opinion that PFOA exposure is capable of causing thyroid disease in humans, supported by epidemiological literature, consideration of alternative explanations, and discussion of dose-response.
   • Specific causation: Dr. Berenji’s differential diagnosis accounted for known risk factors and relied on plaintiffs’ long-term exposure history and blood PFOA levels—reported to be orders of magnitude above background—and available water concentration data.
   • The Court of Appeals has explicitly declined to require exact quantification of exposure levels under Parker and Cornell v 360 W. 51st St. Realty, LLC, 22 NY3d 762 (2014), and the experts’ methodologies fit comfortably within those precedents.
3. Ordering the evidentiary hearing was an abuse of discretion.
   • While trial courts have discretion to order evidentiary hearings, that discretion has limits. Here, where the experts’ methods were neither novel nor inadequate under Parker, a hearing was unnecessary and improper.
   • Consequently, Saint-Gobain’s motions to preclude the experts and for summary judgment “should have been denied in their entirety.”

The court accordingly reversed the order “on the law, with costs,” and denied the defendant’s motions.

IV. Detailed Analysis

A. Precedents Cited and Their Role in the Court’s Reasoning

1. The Frye Framework and Its Interpretation

• Frye v United States, 293 F 1013 (DC Cir 1923)
  The classic decision requiring that “novel scientific evidence” must be based on principles and methods that have gained “general acceptance” in the relevant scientific community. New York adheres to Frye, not the federal Daubert standard, for determining the admissibility of expert scientific testimony.
• People v Wilson, 192 AD3d 1379 (3d Dept 2021)
  Cited for the proposition that the “singular purpose” of a Frye hearing is to determine whether the methods used to generate novel scientific evidence are generally accepted and reliable. This emphasizes that Frye focuses on methodology, not on whether a court agrees with an expert’s conclusions.
• Guerra v Ditta, 185 AD3d 667 (2d Dept 2020), quoting People v LeGrand, 8 NY3d 449 (2007)
  These cases explain that a court need not hold a Frye hearing if it can look to prior decisions in other cases as evidence that a methodology is generally accepted. Marpe relies on this principle to say, in essence: We already have judicial confirmation that these expert methods (and even these very experts) are accepted; another hearing is redundant.
• People v Vaughn, 43 NY3d 190 (2024)
  Cited for the same point: previous rulings can obviate the need for a Frye hearing. Marpe uses this to emphasize that Frye is not to be reflexively invoked whenever expert science is contested.
• People v Brooks, 31 NY3d 939 (2018); People v Johnston, 192 AD3d 1516 (4th Dept 2021)
  These decisions underscore that absent a “novel or experimental scientific theory,” a Frye hearing is “generally unwarranted.” Marpe squarely applies this rule: PFOA epidemiology, differential diagnosis, and medical monitoring are not novel.
• Lipschitz v Stein, 65 AD3d 573 (2d Dept 2009); Parker v Crown Equip. Corp., 39 AD3d 347 (1st Dept 2007)
  These cases delineate the line between:
  • Challenges to the soundness of methodology (a Frye issue), versus
  • Attacks on the persuasiveness or correctness of an expert’s conclusions (which go to weight, not admissibility).

  In Marpe, the court notes that Saint-Gobain’s arguments largely attacked the experts’ conclusions about causation rather than the general acceptance of their methods. Under Lipschitz and similar authorities, such disputes are for cross-examination and jury evaluation, not for preclusion under Frye.

2. The Parker Causation Framework

• Parker v Mobil Oil Corp., 7 NY3d 434 (2006)
  This is the seminal New York Court of Appeals decision governing causation in toxic-tort cases. It requires that expert testimony on causation:
  1. Sets forth the plaintiff’s exposure to the toxin;
  2. Shows that the toxin is capable of causing the particular illness at issue (general causation); and
  3. Demonstrates that the plaintiff was exposed to sufficient levels of the toxin to cause the illness (specific causation).

  Marpe quotes Parker (via People v Wesley, 83 NY2d 417 [1994]) to emphasize the shift from Frye’s focus on general scientific acceptance to a case-specific assessment of whether the expert’s procedures and reasoning reliably support causation.

• Cornell v 360 W. 51st St. Realty, LLC, 22 NY3d 762 (2014)
  Cornell clarified and built upon Parker. Among other things, it:
  • Reaffirmed the importance of both general and specific causation.
  • Stated that while quantitative exposure assessments (e.g., precise dose calculations) can be helpful, exact quantification is not always necessary for admissible causation testimony.

  Marpe relies on Cornell to support Dr. Berenji’s specific causation opinions, even though she did not provide exact numeric dose reconstructions, because she relied on documented blood levels and water concentrations, along with medical history and risk factors, in a scientifically acceptable way.

• People v Wesley, 83 NY2d 417 (1994)
  Although originally a DNA evidence case, Wesley is frequently cited for its articulation of the shift from bare Frye “general acceptance” to a more nuanced inquiry into the reliability of specific procedures and their application. Marpe uses Wesley (via Parker) to justify looking at whether the experts’ procedures were reliable and sufficiently grounded in data—not whether their methods were new.

3. Precedents Involving Epidemiology, Differential Diagnosis, and PFOA

• Jackson v Nutmeg Tech., Inc., 43 AD3d 599 (3d Dept 2007); Nonnon v City of New York, 88 AD3d 384 (1st Dept 2011)
  These cases confirm that reliance on epidemiological studies is a standard, non-novel method for establishing causal relationships between chemical exposure and disease in toxic-tort litigation. Marpe cites them to support the admissibility of Dr. Savitz’s epidemiological general causation testimony without a Frye hearing.
• Cornell (again) and B.T.N. v Auburn Enlarged City Sch. Dist., 45 AD3d 1339 (4th Dept 2007)
  These cases recognize differential diagnosis—a physician’s method of ruling in and ruling out potential causes of a patient’s condition—as a generally accepted method of establishing specific causation. Marpe accordingly holds that Dr. Berenji’s approach is not novel and does not justify a Frye hearing.
• PFOA-specific litigation:
  • Burdick v Tonoga, Inc., Sup Ct, Rensselaer County, Index No. EF2016-253835
    New York state trial court decisions in Burdick had already found Dr. Savitz’s PFOA general causation testimony admissible without a Frye hearing, and recognized Dr. Ducatman’s medical monitoring testimony as generally accepted. Marpe explicitly relies on those rulings.
  • Baker v Saint-Gobain Performance Plastics Corp., 2021 WL 2548825, 2021 US Dist LEXIS 117558 (NDNY 2021)
    A federal case applying the Daubert standard, which found that the same or similar expert testimony regarding PFOA exposure had gained acceptance in the relevant scientific community. Marpe uses this as persuasive support for general acceptance under Frye.
  • Sullivan v Saint-Gobain Performance Plastics Corp., D. Vt., July 15, 2021, Case No. 5:16-CV-125
    A federal decision similarly upholding Dr. Ducatman’s medical monitoring opinions under Daubert. Again, Marpe points to this as evidence that such testimony is part of mainstream scientific practice, negating any claim of novelty.

4. Discretion and Abuse of Discretion

• Matter of Verdugo, 206 AD3d 577 (1st Dept 2022)
  Cited for the proposition that while trial courts enjoy discretion, that discretion “is not without boundaries.” Marpe uses this to underscore that ordering a Frye/Parker hearing when the record clearly demonstrates non-novel, admissible expert methodologies is beyond permissible discretion and qualifies as an abuse.

B. The Court’s Legal Reasoning

1. Drawing a Sharp Line Between Frye and Substantive Causation Attacks

The central move in the court’s reasoning is to separate:

• Challenges to the novelty or general acceptance of scientific methods (a matter for Frye and judicial gatekeeping); from
• Challenges to the reliability, strength, or correctness of an expert’s causal inference from data using accepted methods (a matter for cross-examination, competing experts, and ultimately the factfinder).

The court characterizes Saint-Gobain’s motions as focusing “primarily” on the reliability of the conclusions rather than on any novelty in the methods. That framing is crucial: under New York law, disputes over the interpretation of data, potential confounders, or the weight of the epidemiological evidence ordinarily do not trigger a Frye hearing.

To the limited extent that Saint-Gobain’s arguments might be read as implicating Frye, the court finds that:

• Epidemiological analysis of PFOA and thyroid disease (Savitz),
• Differential diagnosis of the plaintiffs’ thyroid conditions (Berenji), and
• Assessments of the need for medical monitoring (Ducatman)

are each based on non-novel, well-accepted methodologies. After prior state and federal rulings expressly approving very similar testimony, holding a new Frye hearing is unnecessary and improper.

2. Application of the Parker Framework Without an Evidentiary Hearing

Having held that Frye is not triggered, the court then applies the Parker standard to the written expert submissions themselves, rather than remanding for a live hearing.

a. General Causation – Dr. David Savitz

The court finds that Dr. Savitz:

• Utilized “routine practices” in epidemiology, including synthesis of multiple studies on PFOA and thyroid disease.
• Explicitly addressed whether observed associations are likely causal or spurious (e.g., due to confounding factors).
• Offered more than mere statistical association; he opined that it was “more probable than not” that PFOA exposure is capable of causing thyroid disease in humans.
• Discussed and provided examples of dose-response evidence—i.e., evidence that higher PFOA exposure correlates with greater risk of thyroid disease.

Importantly, the court notes that while the Court of Appeals has said general causation can be shown even absent a precise dose-response relationship, Savitz nonetheless backed his causation opinion with dose-related data, strengthening the foundation.

b. Specific Causation – Dr. Manijeh Berenji

For specific causation, the court emphasizes that:

• Dr. Berenji conducted a differential diagnosis, considering plaintiffs’ individual medical histories and the presence or absence of other known thyroid disease risk factors.
• She relied on substantial evidence of exposure:
  • Long-term consumption of contaminated water; and
  • Blood PFOA levels “orders of magnitude” above background, as well as known PFOA levels in water supplies.
• She concluded that PFOA exposure was a “significant factor” in causing each plaintiff’s thyroid disease.

The court directly addresses the common defense argument that plaintiffs must supply precise quantitative estimates of dose or exposure levels. Citing Parker and Cornell, the court reiterates that exact quantification is not required, provided that:

• The expert reliably shows that the plaintiff’s exposure was sufficiently high to be capable of causing the disease at issue, and
• The expert uses accepted medical and scientific methods to link exposure to the specific plaintiff’s condition.

Here, the combination of blood concentration data, water sampling, and individualized medical evaluation sufficed to meet Parker’s foundational demands at the admissibility stage.

c. Medical Monitoring – Dr. Alan Ducatman

The court deals more briefly with Dr. Ducatman, but its conclusion is sweeping: courts here and elsewhere have already found his medical monitoring methodology to be generally accepted, and he has previously been permitted to testify on PFOA-related monitoring without a Frye or Daubert hearing. This makes clear that his testimony, too, is not “novel.”

3. Abuse of Discretion in Ordering the Hearing

Recognizing that trial courts ordinarily enjoy broad discretion to manage their dockets and evidentiary issues, the Third Department nonetheless holds that this discretion has boundaries. Given:

• The established acceptance of the experts’ methods,
• The prior rulings in closely related PFOA cases admitting these same or similar experts, and
• The sufficiency of the written submissions under Parker,

the court finds that ordering an evidentiary hearing was an abuse of discretion. Rather than merely signaling caution, the hearing order effectively treated established methodologies as suspect and threatened to convert routine admissibility disputes into mini-trials, contrary to controlled gatekeeping principles.

Consequently, the Appellate Division not only vacates the hearing order but goes further and holds that the defendant’s motions to preclude and for summary judgment “should have been denied in their entirety.”

C. Impact on Future Cases and the Relevant Area of Law

1. Direct Impact on New York PFOA Litigation

Marpe has immediate and concrete effects on PFOA litigation in New York:

• It effectively establishes that the key expert methodologies used to link PFOA exposure to thyroid disease—epidemiology for general causation, differential diagnosis for specific causation, and medical monitoring opinions—are not novel and are generally accepted.
• It signals that efforts by PFOA defendants to force Frye hearings on these methodologies are likely to fail and may even be characterized as an abuse of discretion if a trial court grants them absent specific, new methodological issues.
• It reinforces and leverages earlier trial and federal decisions (Burdick, Baker, Sullivan) by giving them appellate imprimatur in the New York state system.

2. Broader Implications for Toxic-Tort Practice

Beyond PFOA, the decision has broader ramifications:

• Narrowing the circumstances requiring a Frye hearing.
  Trial courts are reminded that a hearing is not a default response whenever an expert is challenged. It is reserved for truly novel methods or scientific theories. Where standard tools (epidemiology, differential diagnosis) are used, Frye is typically not implicated.
• Emphasizing reliance on prior rulings.
  The court encourages reliance on existing New York and federal rulings about the same or similar methodologies to avoid repetitive hearings. This conserves judicial resources and provides predictability for litigants.
• Clarifying the role of Parker at the motion stage.
  Marpe underscores that Parker is a foundation and reliability inquiry, not a demand for perfect data. Courts should ask whether the expert:
  • Identifies a plausible exposure pathway and sufficient exposure;
  • Shows that the toxin is capable of causing the disease; and
  • Reasonably connects the exposure to the plaintiff’s condition using accepted principles.
  A plaintiff need not meet the level of proof required at trial or for ultimate causation at summary judgment to merely cross the threshold of admissibility.
• Limiting the use of expert-preclusion motions as dispositive tools.
  The decision implicitly cautions defendants against using Frye/Parker motions as a quasi-summary judgment shortcut by attacking the weight of expert evidence under the guise of admissibility. Such tactics may now face more skeptical appellate review.

3. Interaction with Federal Daubert Jurisprudence

Although New York adheres to Frye, Marpe openly relies on prior federal Daubert rulings (Baker and Sullivan) to establish that certain PFOA expert methods have gained acceptance. This suggests a practical convergence:

• Federal Daubert decisions about methodological reliability can be persuasive evidence of “general acceptance” under Frye.
• Parties may increasingly cite federal mass-tort rulings in New York state court to support or challenge the novelty of scientific testimony.

V. Complex Concepts Simplified

1. PFOA (Perfluorooctanoic Acid)

PFOA is a synthetic chemical used in manufacturing non-stick cookware, water-resistant fabrics, and various industrial products. It is:

• Highly persistent in the environment and in human bodies (a “forever chemical”).
• Capable of accumulating in blood and tissues over time.
• Associated in scientific studies with various health outcomes, including thyroid disease, cancer, and immune dysfunction.

2. General vs. Specific Causation

• General causation asks: Is the substance (here, PFOA) capable of causing the type of disease alleged (e.g., thyroid disease) in humans, at some level of exposure? This is typically addressed using:
  • Epidemiological studies in exposed populations;
  • Toxicology and animal studies; and
  • Mechanistic or biological plausibility evidence.
• Specific causation asks: Did this substance, in this person’s actual exposure circumstances, play a substantial role in causing this individual’s specific disease? This is typically addressed by:
  • Reconstructing or estimating exposure levels;
  • Reviewing the person’s medical history and other risk factors;
  • Using a differential diagnosis to rule out alternative explanations.

3. Differential Diagnosis

A differential diagnosis is the process by which a physician:

1. Identifies all plausible causes of a patient’s symptoms or disease, and
2. Systematically rules in or rules out each possibility based on available evidence (tests, history, risk factors) until arriving at the most likely cause(s).

In toxic-tort litigation, differential diagnosis is used to determine whether a toxic exposure is a substantial contributing factor to a disease by:

• Considering non-toxic causes (genetic, lifestyle, idiopathic);
• Assessing whether the plaintiff’s exposure greatly exceeded background levels; and
• Determining whether the timing and progression of the disease fit with known effects of the toxin.

4. Dose-Response Relationship

A “dose-response” relationship exists when:

• The risk or severity of an outcome increases as the dose or exposure level increases.

In causation analysis:

• Evidence of dose-response supports the inference that a relationship is causal, not merely coincidental.
• However, as Parker and Cornell recognize, an expert can sometimes establish causation even without a fully quantified dose-response curve, especially where the plaintiff’s exposure was clearly far above normal background levels and the literature supports causal mechanisms.

5. The Frye Standard vs. the Daubert Standard

• Frye (New York’s standard):
  • Focuses on whether the expert’s underlying principles and methods have achieved “general acceptance” in the relevant scientific community.
  • Is primarily concerned with novel or experimental techniques.
  • Does not require the court to independently scrutinize the logic of the expert’s conclusions once the method is accepted.
• Daubert (federal standard):
  • Requires a multi-factor reliability assessment of methodology (testability, peer review, error rates, standards, and general acceptance, among others).
  • Gives judges a more active “gatekeeping” role, sometimes involving close evaluation of the reasoning from data to conclusion.

In Marpe, the court applies Frye but still finds federal Daubert-based rulings useful as evidence that the relevant methodologies have gained acceptance in the scientific community.

6. Abuse of Discretion

“Abuse of discretion” is a standard of appellate review applied when a lower court has broad leeway (discretion) to make a decision, but that leeway is not unlimited. An appellate court may find an abuse of discretion where the trial court:

• Applies the wrong legal standard,
• Ignores binding precedent, or
• Makes a decision that is arbitrary or unsupported by the record.

In Marpe, the Third Department holds that ordering an evidentiary hearing—despite the experts’ use of long-established methodologies and prior rulings approving them—went beyond permissible discretion.

VI. Conclusion

Marpe v. Tonoga, Inc. is an important appellate decision at the intersection of environmental toxic-tort litigation and expert evidence law in New York. Its key contributions are:

• Doctrinal clarification: The decision sharpens the distinction between Frye admissibility (which addresses novel science and general acceptance of methods) and Parker foundational sufficiency (which addresses case-specific reliability and causation).
• Constraint on evidentiary hearings: It limits the circumstances under which trial courts may require resource-intensive Frye hearings, especially in recurring mass-tort contexts where the same experts and methodologies have already been vetted.
• Recognition of PFOA expert methodologies: It confirms that epidemiological analysis, differential diagnosis, and medical monitoring assessments relating to PFOA exposure and thyroid disease are established and admissible methodologies in New York courts.
• Guidance for toxic-tort litigants: Plaintiffs can rely on a well-defined roadmap for constructing causation evidence under Parker, while defendants are constrained from using admissibility challenges as a routine mechanism to foreclose jury consideration of scientific disputes.

In the broader legal landscape, Marpe reinforces a balanced approach to scientific evidence: courts must guard against junk science, but they must not transform settled scientific methods into perpetually litigated “novelties” in each new case. For PFOA and similar environmental torts, this decision will likely streamline proceedings, reduce duplicative gatekeeping litigation, and allow factfinders to focus on the ultimate questions of responsibility and harm.