Atlantic Legal Foundation

Excluding Expert Witness Testimony In Mold Litigation

By Patrick J. Perrone, Whitney A. Klein, and Dr. Judith L. Steinman

[Editor's Note: Patrick J. Perrone is a partner and Whitney A. Klein is an associate in the law firm of McCarter & English, LLP. Dr. Judith L. Steinman is the Director of the Science Group at McCarter & English, LLP. Mr. Perrone and Ms. Klein represent defendants in construction defect and product liability litigation. Dr. Steinman focuses on litigation-related scientific issues. The law firm of McCarter & English, LLP specializes in — among other things — mass tort and insurance coverage litigation on behalf of large and small companies. Copyright 2001 by the authors. Responses to this commentary are welcome].

A. Introduction

Mold litigation is on the rise. More and more plaintiffs are seeking compensation for personal injuries allegedly caused by exposure to mold. To prove their case, plaintiffs rely on expert testimony. [1] In many cases, juries have returned large verdicts. [2] Yet, most cases should never get to the jury since the alleged relationship between mold and injury is unproven and unreliable. [3] This article will focus on the admissibility of expert testimony in mold cases.

B. Typical Fact Pattern

Where roof leaks, window leaks or other leaks exist, mold is likely to grow. [4] Where mold grows, it is possible that individuals exposed to certain mycotoxins in certain molds will get sick. [5] Some of these individuals will file suit and seek to recover damages from builders, architects, and property managers. If a lawsuit is brought, an expert will be retained to testify that exposure to mold and mycotoxins caused the illness.

C. Admissibility of Expert Testimony Under Daubert

In federal courts and numerous state courts, plaintiffs now must meet certain threshold requirements before expert testimony will be admitted. [6] The seminal case on admissibility of expert testimony is Daubert v. Merrell Dow Pharmaceuticals, 509 U.S. 579 (1993). In Daubert, the United States Supreme Court ruled that trial courts must act as "gatekeepers," requiring the proponent of scientific evidence to demonstrate that the expert's opinion is both "reliable" and "relevant." [7]

To "establish a standard of evidentiary reliability," each step in the expert's reasoning must be supported by "good grounds." [8] "Any step that renders the analysis unreliable ... renders the expert's testimony inadmissible." [9] Significantly, an expert's "bald assurance of validity is not enough" to establish admissibility. [10]

In Daubert, the Supreme Court identified several factors that courts should consider in determining whether expert testimony is reliable and admissible. The Court's list — which is not intended to be exhaustive — includes: (1) the extent to which the theory has been or can be tested; (2) whether the theory has been subjected to peer review and/or publication; (3) whether the theory or technique has been generally accepted as valid by the relevant scientific community; and (4) whether there are any relevant governing standards. [11]

Not only must the expert's testimony be reliable, it must be relevant. [12] In other words, there must be a logical connection between the expert's theory and the expert's conclusion. [13] With respect to mold litigation, this means that the expert must be able to demonstrate — by a preponderance of the reliable evidence — that exposure to mold caused plaintiff's injury. Absent such proof, the expert's analysis is unreliable and irrelevant. [14] As discussed in depth below, there is no proven connection between exposure to mold and any particular illness.

D. Plaintiffs Cannot Currently Satisfy the Daubert Criteria

In mold litigation cases, plaintiffs cannot recover unless they prove causation. [15] To prove causation, a plaintiff must prove: (1) that mold generally causes personal injuries; and (2) that mold caused the specific injuries involved in the case. [16]

(1) General causation

Before an expert may testify, the expert must prove general causation. General causation focuses on whether mold is capable of causing a particular injury or condition in the general population. [17]

Epidemiology is the best method of establishing general causation in the toxic torts context. [18] Courts have consistently and universally agreed that epidemiology is the most relevant type of evidence in such cases. [19] Epidemiological studies typically are used to demonstrate that exposure to a particular toxin increases the risk of a particular injury. [20]

Reliance on epidemiological studies is appropriate as long as the study: (1) is properly designed; (2) is properly executed; (3) results in an increased risk; (4) is unbiased in its design; and (5) has a 95% confidence level. [21]

Where the epidemiology fails to demonstrate that the plaintiff's alleged injury was "more likely than not" caused by the toxin at issue, courts typically have ruled that the evidence is not relevant and not admissible. Stated differently, if the epidemiological evidence does not show that exposure to an alleged toxin doubles the risk of a known disease, plaintiff cannot show causation. For instance, in Daubert v. Merrell Dow Pharmaceuticals, Inc., 43 F.3d 1311 (9^th Cir.), cert. denied, 516 U.S. 869 (1995), the Ninth Circuit described the relevant burden of proof as follows:

[P]laintiffs must establish not that their mother's ingestion of Bendectin increased somewhat the likelihood of birth defects, but that it more than doubled it — only then can it be said that Bendectin is more likely than not a source of their injury. [22]

Similarly, in Hall v. Baxter Healthcare, 947 F.Supp. 1387 (D. Or. 1996), the Court stated that plaintiff was required to prove that "exposure to breast implants more than doubled the risk of their alleged injuries." [23]

In addition to epidemiological studies, most courts require compliance with what are referred to as the Bradford Hill criteria. [24] The Bradford Hill criteria are used to determine whether epidemiological evidence is reliable and include, among other things, strength of association, temporal relationship, consistency among studies, biological plausibility, consideration of alternative explanations, specificity of association, dose-response relationship, and experimental evidence. [25] Some courts and commentators require the proponent of scientific evidence to meet the Bradford Hill criteria before evidence of a causal connection between a toxin and a disease will be admitted. For instance, Judge Weinstein of the Southern District of New York has held that if epidemiological studies do not meet any of the Bradford Hill criteria, plaintiff's epidemiological evidence is not reliable. [26] Similarly, David E. Bernstein suggests that "epidemiological evidence that meets none of [Hill's] criteria should be deemed automatically inadmissible under Rule 702." [27]

Significantly, it is not enough to simply establish that epidemiological studies show an elevated risk. Plaintiff must also show that he or she is similarly situated to the individuals in the relevant studies. [28] This requires plaintiff to demonstrate that he or she was exposed to the same toxins as the individuals in the study, that the exposure levels were comparable to the exposure levels of the individuals in the study, and that the exposure occurred before the onset of injury. [29]

Currently, there are no reliable epidemiological studies that demonstrate — by a preponderance of the evidence — a causal connection between mold and a particular illness in the general population. Nor are there any relevant peer review articles establishing such a connection. [30]

(2) Specific causation

Once general causation has been proven, the expert still must prove specific causation. Specific causation focuses on whether a toxic substance caused a particular individual's injury. To establish "specific causation" in a mold case, the plaintiff's experts must demonstrate: (1) there were mycotoxins in the residence; (2) the plaintiff was exposed to the mycotoxins; (3) the dose and duration of exposure to mycotoxins was sufficient to cause plaintiff's injury; and (4) the plaintiff was injured. [31] In mold litigation to date, plaintiffs typically rely on a number of assumptions to prove these points. For example, plaintiffs' experts usually assume that because mold spores are found in a plaintiff's residence: the mold contained mycotoxins; the mycotoxins became airborne; the mycotoxins entered the plaintiff's body by inhalation or ingestion; and the mycotoxins existed in sufficient enough quantities to cause plaintiff's injuries. Such assumptions — however — cannot be used to establish specific causation. Rather, plaintiff must establish that exposure to a certain level of toxin is harmful and that plaintiff was exposed to those levels. [32]

Currently, there is no biological marker to indicate whether a person has ingested, inhaled or absorbed mycotoxins from various mold spores. [33] Absent a reliable biological marker to indicate the presence or absence of mycotoxins within the body, it is not possible to determine whether a plaintiff was exposed to such mycotoxins. [34] Similarly, there is no test currently available to determine the amount of mycotoxins to which a person might have been exposed. [35] If an expert cannot identify the level of toxin to which a plaintiff was exposed, the expert cannot testify about specific causation. [36]

E. Conclusion

To prove their case, plaintiffs must prove through expert testimony that exposure to mold caused their particular illness. As things currently stand, there is no reliable evidence supporting such a conclusion. Accordingly, defense counsel should insist on in limine hearings on the admissibility of expert testimony. By insisting on such hearings — which numerous courts encourage — defense counsel will ensure that only reliable evidence is presented to the jury. [37]

NWK2: 804176.01

[1] See, e.g., Ballard v. Fire Ins. Exchange, No. 99-05252 (Tex. Dist. Ct. 2001), 1 Mealey's Litig. Rep.: Mold 3 (March 2001).

[2] New Haverford Partnership v. Stroot, No. 95-C-05-074-HLA (Del. Sup. 2000), Mealey's Litig. Rep.: Mold (Nov. 2000) ($1 million verdict); Anderson v. Allstate Ins. Co., No. 01-15330 (9^th Cir. 2001), 1 Mealey's Litig. Rep.: Mold 3 (March 2001) ($3 million verdict).

[3] See Journal of Controversial Medical Claims, Mold and Mold Toxins; The Newest Toxic Tort, Ronald E. Gots, M.D., Ph.D., Vol. 8 No. 1, Feb. 2001.

[4] Id.

[5] Id.

[6] An excellent review of state law on the admissibility of expert testimony is provided in Daubert and its Progeny: Scientific Evidence in Product Liability Litigation, Frederick T. Smith, Washington Legal Foundation, Washington, D.C. (2000).

[7] Daubert v. Merrell Dow Pharmaceuticals, 509 U.S. 579, 589 (1993).

[8] Id. at 590.

[9] In re Paoli R.R. Yard PCB Litigation, 35 F.3d 717, 745 (3^rd Cir. 1994) (emphasis in original).

[10] Daubert v. Merrell Dow Pharmaceuticals, Inc., 43 F.3d 1311, 1315 (9^th Cir.), cert. denied, 516 U.S. 869 (1995).

[11] Daubert v. Merrell Dow Pharmaceuticals, 509 U.S. at 594.

[12] Id. at 593.

[13] U.S. v. Downing, 753 F.2d 1224, 1237 (3rd Cir. 1985) (court requires an appropriate "fit" between the proffered theory and the disputed issues).

[14] As the U.S. Supreme Court explained in Daubert v. Merrell Dow Pharm, Inc., 509 U.S. 579 (1993): "The study of the phases of the moon, for example, may provide valid scientific "knowledge" about whether a certain night was dark, and if darkness is a fact in issue, the knowledge will assist the trier of fact. However (absent grounds supporting such a link), evidence that the moon was full on a certain night will not assist the trier of fact in determining whether an individual was likely to have behaved irrationally on that night." Id. at 591.

[15] In tort law, "causation" is the linchpin joining substance and disease. Without expert testimony supporting causation, the cause of action typically fails. Daubert and its Progeny: Scientific Evidence in Product Liability Litigation, Frederick T. Smith, Washington Legal Foundation, Washington, D.C. (2000).

[16] See, e.g., Merrell Dow Pharmaceuticals v. Havner, 953 S.W.2d 706, 714-15 (Tex. 1997) (noting that "general causation" is whether a substance is capable of causing a particular injury in the general population and that "specific causation" is whether a substance caused a particular individual's injury).

[17] See Id. at 714-15.

[18] See, e.g., Brock v. Merrell Dow Pharmaceutical, Inc., 874 F.2d 307, 311 (5^th Cir.) ("The most useful and conclusive type of evidence in a case such as this is epidemiological studies."), modified, 884 F.2d 166 (1989), cert. denied, 494 U.S. 1046 (1990); Conde v. Velsicol Kim. Corp., 804 F. Supp. 972, 1025-26 (S.D. Ohio 1992) ("Epidemiological studies are the primary generally-accepted methodology for demonstrating a causal relation between a chemical compound and a set of symptoms or a disease"), aff'd, 24 F.3d 809 (6^th Cir. 1994).

[19] First Circuit: Lynch v. Merrell-National Laboratories, 830 F.2d 1190 (1^st Cir. 1987); Second Circuit: In re Agent Orange Product Liability Litigation, 611 F.Supp. 1223, 1231 (E.DN.Y. 1985); (Weinstein, J., presiding), aff'd, 818 F.2d 187 (2d Cir. 1987), cert. denied, 487 U.S. 1234 (1988); Third Circuit: Wade v. Greaux v. Whitehall Laboratories, Inc., 874 F.Supp. 1441, 1483 (D.V.I. 1994), aff'd, 46 F.3d 1120 (3d Cir. 1994); Fourth Circuit: Marder v. GD. Searle & Co., 630 F.Supp. 1087, 1092-95 (D. Md. 1986), aff'd, 814 F.2d 655 (4^th Cir. 1977); Fifth Circuit: Allen v. Pennsylvania Engineering Corp., 102 F.3d 194, 197 (5^th Cir. 1996); Sixth Circuit: Elkins v. Richardson-Merrell, 8 F.3d 1068, 1073 (6^th Cir. 1993), cert. denied, 510 U.S. 1193 (1994); Seventh Circuit: Porter v. WhiteHall Laboratories, Inc., 791 F.Supp. 1335, 1347 (S.D. Ind. 1992), aff'd, 9 F.3d 147 (7^th Cir. 1993); Eighth Circuit: Sorenson v. Shaklee Corp., 31 F.3d 638, 641 (8^th Cir. 1994); Ninth Circuit: Daubert v. Merrell Dow Pharmaceuticals, Inc., 43 F.3d 1311, 1320-21 (9^th Cir.), cert. denied,. 516 U.S. 869 (1995); Tenth Circuit: Wilson v. Merrell Dow Pharmaceuticals, Inc., 893 F.2d 1149, 1154 (10^th Cir. 1990); Eleventh Circuit: Haggerty v. Upjohn Co., 950 F. Supp. 1160, 1165 (S.D. Fla. 1996), aff'd, 158 F.3d 488 (5^th Cir. 1998).

[20] "To calculate relative risk, the number of occurrences of an injury or a defect in an exposed group is divided by the number of occurrences in the control or unexposed group. If the given injury occurs with equal frequency between the exposed and controlled groups, the relative risk would be 1.0. A relative risk of 1.0 indicates that exposure is not associated with injury. A relative risk of greater than 1.0 suggests that the substance may cause injury." Daubert and its Progeny: Scientific Evidence in Product Liability Litigation, Frederick T. Smith, Washington Legal Foundation, Washington, D.C. (2000).

[21] Merrell Dow Pharmaceuticals v. Havner, 953 S.W.2d 706, 717-719 (Tex. 1997). Frederick T. Smith provides a cogent explanation of the 95% confidence interval in his Monograph entitled Daubert and its Progeny: Scientific Evidence and Product Liability Litigation, Frederick T. Smith, Washington Legal Foundation, Washington, D.C. (2000). Mr. Smith states: "Epidemiologists ordinarily use a confidence interval of 95 percent. At a 95 percent confidence interval, the true relative risk value will be between the high and low ends of the confidence interval 95 percent of the time. If a confidence interval of "95 percent between 0.75 and 1.25" is cited, this means that random repetition of the study should produce 95 percent of the time, a relative risk somewhere between 0.75 and 1.25. Because this confidence interval includes relative risk values both less than and exceeding 1.0, the null value, a researcher cannot state that the results are statistically significant. To be statistically significant, not only must the relative risk greatly exceed 1.0, but the lower confidence interval also must exceed 1.0. The use of confidence intervals of less than 95% has been explicitly rejected by many courts." (Footnotes omitted).

[22] Daubert v. Merrell Dow Pharmaceuticals, Inc., 43 F.3d 1311, 1320-21 (9^th Cir.), cert. denied,. 516 U.S. 869 (1995) (emphasis added).

[23] Hall v. Baxter Healthcare, 947 F. Supp. 1387, 1403 (D. Or. 1996) (emphasis added).

[24] See Austin Bradford Hill, The Environment and Disease: Association or Causation?, 58 Proc. Royal Soc'y Med. 295, 299 (1965).

[25] Merrell Dow Pharmaceuticals v. Havner, 953 S.W.2d 706, 718-19 (Tex. 1997).

[26] In re: Joint Eastern & Southern District Asbestos Litigation, 847 F. Supp. 1014 (S.D.N.Y. 1993).

[27] David E. Bernstein, The Admissibility of Scientific Evidence After Daubert v. Merrell Dow Pharmaceuticals, Inc., 15 CARDOSA L. REV. 2139, 2167-70 (1994).

[28] Merrell Dow Pharmaceuticals v. Havner, 953 S.W.2d 706, 718 (Tex. 1997).

[29] Id.

[30] See Journal of Controversial Medical Claims, Mold and Mold Toxins; The Newest Toxic Tort, Ronald E. Gots, M.D., Ph.D., Vol. 8 No. 1, Feb. 2001: "There are few epidemiological investigations of inhaled mycotoxins and disease in indoor air settings. Although some purport to show an association between inhaled mycotoxins and health effects, none has had sufficient data or experimental design to support this claim."

[31] See Journal of Controversial Medical Claims, Mold and Mold Toxins; The Newest Toxic Tort, Ronald E. Gots, M.D., Ph.D., Vol. 8 No. 1, Feb. 2001.

[32] See, e.g., Austin v. Kerr-McGee Refining Corp., 25 S.W.3d. 280, 292 (Tex. App. 2000); Curtis v. M&S Petroleum, Inc., 174 F.3d 661, 670 (5^th Cir. 1999).

[33] See Journal of Controversial Medical Claims, Mold and Mold Toxins; The Newest Toxic Tort, Ronald E. Gots, M.D., Ph.D., Vol. 8 No. 1, Feb. 2001.

[34] Id.

[35] Id.

[36] See, e.g., Allen v. Pennsylvania Engineering Corp., 102 F.3d 194, 198-99 (5^th Cir. 1996) (affirming judgment as a matter of law where expert failed to show that plaintiff was exposed to toxic levels sufficient to cause plaintiff's injury); Christophersen v. Allied-Signal Corp., 939 F.2d. 1106, 1114-1115 (5^th Cir. 1991), cert. denied, 503 U.S. 912 (1992) (District Court properly excluded expert's opinion where expert had insufficient data concerning plaintiff's level of exposure to an allegedly dangerous substance); Castellow v. Chevron U.S.A., 97 F.Supp.2d. 780, 796-97 (S.D. Tex. 2000) (court held that expert should not be permitted to testify where expert cannot quantify plaintiff's level of exposure to alleged toxins).

[37] See, e.g., Holbrook v. Lykes Bros. Steamship, Co., 80 F.3d. 777, 784 (3^rd Cir. 1996) (encouraging in limine hearing); Hoes v. Chicago Northwestern Transportation Co., 70 F.3d 968, 973 n.3 (8^th Cir. 1995) (same).