The Role Of Toxicology In Tort Litigation
In a product-liability or toxic-tort lawsuit, toxicological evidence may be offered when there are claims that chemical exposure caused a disease or injury. (1) Toxicology is the science of poisons. (2) It “deals with poisons and their effect on living organisms, [and] with substances otherwise harmless that prove toxic under particular conditions.” (3)
Toxicological studies alone, however, rarely offer direct evidence that exposure to a chemical caused a disease in any one individual. (4) Instead, toxicology can explain the increased risk of contracting a disease at a particular dose or exposure, and can help rule out other risk factors for the disease. (5) Toxicological studies help answer two main questions:
1. What hazards does a chemical or physical agent present to human populations or the environment?
2. What degree of risk is associated with chemical exposure at any given dose? (6)
As a field of study, toxicology is related to epidemiology. Both sciences address the causal relationship between chemical exposure and disease. (7) While toxicology attempts to determine at what doses foreign agents produce their effects, epidemiology focuses on the incidence and distribution of diseases in human populations. (8)
From a judicial perspective, the main difference is that courts generally admit expert opinions concerning epidemiology, but often view toxicological studies with more suspicion. (9) Admitting toxicological evidence is more controversial because it involves extrapolating from chemical exposure tests on animals, or on isolated tissue samples, to human beings. (10) The question in each case is how reliably the extrapolation can be made.
For either discipline, the proponent of scientific evidence must establish “that the methodology used is reliable and in the particular instance produced reliable results.” (11) This requirement has important implications for tort litigation, where the lack of admissible expert testimony may determine the outcome of a lawsuit. In Minnesota, for example, we have seen that if toxicological evidence does not reliably establish a causal link between chemical exposure and claimed health problems, a lawsuit based on that evidence cannot proceed to trial.
I. THE MINNESOTA APPROACH TO NOVEL SCIENTIFIC EVIDENCE
Minnesota has rejected the federal Daubert standard for novel scientific evidence. (12) Instead, Minnesota follows a two-pronged admissibility standard, called the Frye-Mack test. (13) Under Frye-Mack, the trial court determines whether the evidence is generally accepted in the relevant scientific community. (14) In addition, the scientific evidence must have foundational reliability. (15)
To establish foundational reliability, the proponent must demonstrate that “the test itself is reliable and that its administration in the particular instance conformed to the procedure necessary to ensure reliability.” (16) Moreover, as with other expert testimony, the evidence has to satisfy applicable evidentiary rules. That is, the evidence must “be relevant, be given by a witness qualified as an expert, and be helpful to the trier of fact.” (17)
In adopting the Frye-Mack standard for admission of novel scientific evidence, the Minnesota Supreme Court sought to achieve consistency in judicial decisions, while maintaining a gate-keeping role for the trial courts. The court expressed concern that adopting Daubert might lead to non-uniformity in judicial decisions on novel scientific evidence. (18) It explained that “the Frye-Mack standard for admission ‘facilitates more objective and uniform rulings’ by the courts while a standard based solely on the rules of evidence introduces an ‘undesired element of subjectivity … [into] evidentiary rulings.’” (19)
Under the Frye general acceptance standard, trial judges are asked to defer to the scientific community’s assessment of a given technique, rather than decide scientific validity themselves. In this way, Frye-Mack is intended to ensure “objective and uniform rulings” as to particular scientific methods or techniques. (20)
On appeal, the standard of review for admissibility determinations is a two-step approach. Whether a particular scientific principle or technique satisfies the first prong of the Frye-Mack standard — general acceptance in the relevant scientific field — is a question of law subject to de novo review on appeal. Trial court decisions under the second prong — foundational reliability — are reviewed under an abuse-of-discretion standard, as are determinations of expert witness qualifications and helpfulness. (21)
II. APPLYING MINNESOTA’S FRYE-MACK STANDARD TO TOXICOLOGICAL EVIDENCE
Minnesota’s approach to the admissibility of toxicological evidence is best illustrated by Goeb v. Tharaldson. (22) In that case, the Goeb family alleged that they suffered permanent injuries from exposure to an insecticide. (23) Pretrial motions questioned whether the insecticide actually caused their health problems.
The Goebs had rented a house for themselves and their son. Before they moved in, the landlord hired a pest control company to deal with an ant infestation problem. The exterminator used a number of chemicals, including Dursban, an insecticide manufactured by Dow Chemical Company. (24) Shortly after moving into the home, the family began complaining of health problems they associated with a “chemical odor” in the house. The symptoms included headaches, nausea, diarrhea, intestinal cramping, sore throats, and general malaise. (25)
The Goebs asked the exterminator, and Dow Chemical Company, whether their symptoms could be related to the insecticides used in the home. (26) The future defendants reassured the Goebs that the insecticides were not causing health problems, and told the Goebs to air out the house to get rid of the chemical odor. (27)
Although medical tests on the family appeared to be normal, the family moved out of the house over concerns for their health. (28) The county health department initiated an investigation, and concluded that the family’s exposure to the active ingredient in Dursban (chlorpyrifos) was “a reasonable explanation for the family’s illness while living in the house.” (29) Yet, the chemical exposure did not explain the illnesses experienced by the family after they moved out of the house. (30)
The Goeb family sued both the exterminator and Dow Chemical Company. They identified two expert witnesses, who would testify that the family sustained permanent brain damage and other illnesses from exposure to Dursban. (31) Both experts were medical doctors with over 30 years of experience, including substantial experience in toxicology. (32) One of the experts had lectured on toxicology for many years, and had written numerous articles on pesticide toxicology, including articles in peer-reviewed journals discussing chlorpyrifos. (33)
The trial court granted Dow’s motions to exclude the expert testimony, finding that the experts’ methodologies were not generally accepted and were unreliable. (34) Neither expert addressed the dose-response relationship between exposure and illness, nor identified the amount of chlorpyrifos needed to cause the claimed health conditions. (35) Both experts relied “to an inappropriate degree on a temporal relationship between an unquantified exposure and claimed but unverified symptomatology.” (36)
Without expert testimony to establish a prima facie case that their illnesses were caused by exposure to Dursban, the Goebs were missing a key element of their claim. Therefore, the trial court granted summary judgment to Dow on the issue of causation, and thereafter granted Dow summary judgment on all claims. (37)
The Minnesota Supreme Court affirmed exclusion of the plaintiffs’ experts, and upheld summary judgment. (38) Focusing on the second prong of the Frye-Mack standard — foundational reliability — the court held it was not an abuse of discretion to exclude the plaintiffs’ expert testimony. (39) Neither expert reviewed all of the family’s pre-exposure and post-exposure medical records. Instead, they primarily relied on questionnaires and oral histories from the family. (40) The court also found that documents and literature relied upon by the experts, as well as testing developed for the litigation, were unreliable. (41)
With the evidence remaining after exclusion of their experts, the plaintiffs were unable to prove that chemical exposure caused their illnesses. (42) Lacking reliable causation evidence, the Goebs could not proceed with their lawsuit.
III. LOOKING TO THE FUTURE
Scientific evidence can be critically important in tort litigation. When a question arises as to whether chemical exposure caused a disease or illness, experts on both sides of the dispute are needed to explain the evidence, and to shed light on the acceptance and reliability of the scientific methods or techniques involved. The outcome of a lawsuit, as in Goeb v. Tharaldson, may depend on it.
For the foreseeable future, Minnesota will adhere to the Frye-Mack evidentiary standard, and remain steadfast in its rejection of the federal Daubert approach to novel scientific evidence. (43) Heeding expectations for consistency in the law, the Minnesota Supreme Court “will only abandon Frye-Mack if the reasons for departing from that standard greatly outweigh those for retaining it.” (44) How Minnesota courts will apply that standard, to novel toxicological evidence in product-liability and toxic-tort actions, remains to be seen.
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1 See, e.g., Goeb v. Tharaldson, 615 N.W.2d 800, 803-07 (Minn. 2000) (plaintiffs proffered evidence to support claims that exposure to an insecticide caused adverse health conditions).
2 B. Goldstein & M. Henifin, Reference Guide on Toxicology, 403 (contained in the Reference Manual on Scientific Evidence, 401-37 (2nd ed., Fed. Judicial Ctr. 2000)).
3 Webster’s Third New International Dictionary, 2419 (1993).
4 Reference Guide on Toxicology, at 403.
5 Id.
6 Id.
7 Id. at 413.
8 Id. at 403, 413; see M. Green, D. Freedman & L. Gordis, Reference Guide on Epidemiology, 335-36 (contained in the Reference Manual on Scientific Evidence, 333-400 (2nd ed., Fed. Judicial Ctr. 2000)); see alsoThe Use of Epidemiology in Tort Litigation: A Survey of Federal and State Jurisdictions (ABA June 2003).
9 Reference Guide on Toxicology, at 413-14.
10 Id.
11 Goeb v. Tharaldson, 615 N.W.2d 800, 816 (Minn. 2000).
12 Id. at 814 (rejecting the expert evidentiary standard established in Daubert v. Merrill Dow Pharmaceuticals, Inc., 509 U.S. 579, 587, 113 S. Ct. 2786 (1993)).
13 Goeb, 615 N.W.2d at 814. The Frye-Mack standard is named after two cases: Frye v. United States, 293 F. 1013 (D.C. Cir. 1923) and State v. Mack, 292 N.W.2d 764, 768-69, 772 (Minn. 1980).
14 Goeb, 615 N.W.2d at 814 (citing State v. Moore, 458 N.W.2d 90, 97-98 (Minn. 1990) and State v. Schwartz, 447 N.W.2d 422 (Minn. 1989)).
15 Goeb, 615 N.W.2d at 814.
16 Id. (quoting Moore, 458 N.W.2d at 98).
17 Id. (citing Minn. R. Evid. 402 and 702). Minnesota’s evidentiary rules in this regard are identical, in relevant part, to Rules 402 and 702 of the Federal Rules of Evidence.
18 Id. at 814.
19 Id. at 810 (quoting State v. Schwartz, 447 N.W.2d 422, 424 (Minn. 1989)).
20 Goeb, 615 N.W.2d at 810.
21 Id. at 815. For a more detailed discussion of Minnesota’s approach to the admissibility of novel scientific evidence, see 11 Minn. Prac., Evidence § 703.04 (3rd ed. 2001 & Supp. 2003).
22 615 N.W.2d 800 (Minn. 2000). In fact, Goeb is currently the only reported Minnesota decision discussing toxicological evidence in the context of a product-liability or toxic-tort lawsuit. Other uses of toxicological evidence, such as the use of forensic toxicology in criminal cases or in dram-shop actions, are beyond the scope of this article.
23 Goeb, 615 N.W.2d at 803.
24 Id.
25 Id. at 803-04.
26 Id. at 804.
27 Id.
28 Id. at 804.
29 Id. at 804-05.
30 Id. at 805.
31 Id. at 805.
32 Id. at 805-07.
33 Id. at 805.
34 Id. at 808.
35 Id. at 808-09.
36 Id. at 809.
37 Id.
38 Id. at 816-17.
39 Id. at 815-16.
40 Id. at 816. “The self-reporting of a plaintiff’s medical history in preparation for litigation, without additional independent confirmation, is inherently unreliable.” Id. The trial court also found that the experts did not perform an “appropriate” differential diagnosis. Nor did they consider the “no observed effect level” established for Dursban. Id. at 809. The “no observed effect level,” or NOEL, is determined through a toxicological dose-response study. Id. at 808 & n.6. The NOEL is considered a threshold level above which observable effects in test animals are believed to occur, and below which no toxicity is observed. Id. n.6.
41 Id. at 815-16.
42 Id. at 817.
43 Minnesota’s rejection of Daubert has received mixed reviews. Compare P. Knapp, The Other Shoe Drops: Minnesota Rejects Daubert, 27 Wm. Mitchell L. Rev. 997 (2000) (arguing that Minnesota’s Frye-Mack approach may provide “the best of both worlds” in achieving consistency and gate-keeping with respect to novel scientific evidence) With Comment, Minnesota Decides: Goeb v. Tharaldson and the Admissibility of Novel Scientific Evidence, 24 Hamline L. Rev. 460 (2001) (arguing that the Minnesota Supreme Court should have adopted the Daubert standard).
44 Goeb, 615 N.W.2d at 812. |
