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October 06, 2014 Articles

Expert Testimony on Causation Requires Sufficient Scientific Basis

Pennsylvania reinforces minimum standard to be met to qualify as expert opinion.

By John J. DiChello

In a precedential ruling on the admissibility of expert testimony that is particularly significant to defendants in toxic tort matters, a three-judge panel of the Superior Court of Pennsylvania in Snizavich v. Rohm & Haas Co., 83 A.3d 191 (Pa. Super. Ct. 2013), ruled on December 6, 2013, that an expert's opinion regarding the cause of a plaintiff's injury is inadmissible under Pennsylvania Rule of Evidence 702 and the Frye standard if it is not based on scientific authority, such as facts, empirical studies, or the expert's research, that the expert has applied to the facts of the case and that supports the expert's opinion. This is so even if the expert relied on many years of experience in medical or scientific fields and his or her own knowledge.

In Snizavich, the decedent was employed as a contractor at Rohm and Haas's facility in Spring House, Pennsylvania, for 13 years, during which time he worked on air conditioning, refrigeration, and environmental chambers and allegedly came into contact with various chemicals. The decedent subsequently died from brain cancer. The plaintiff, who was the decedent's wife, sued Rohm and Haas, contending that her husband's brain cancer was caused by exposure to chemicals at the Spring House facility and that Rohm and Haas was liable for her husband's death under the Wrongful Death and Survival Acts, 42 Pa. Cons. Stat. §§ 8301(a) and 8302.

Rohm and Haas moved for summary judgment due to the absence of expert testimony on causation, an essential element of the plaintiff's claims. That motion prompted the plaintiff to submit the expert report of Thomas H. Milby, M.D. and resulted in the denial of Rohm and Haas's motion. Thereafter, Rohm and Haas moved to exclude Dr. Milby's testimony under Pennsylvania Rule of Evidence 702 and Frye v. United States, 293 F. 1013 (D.C. Cir. 1923). The trial court ruled that Dr. Milby's testimony was inadmissible because it was not based on any scientific or technical methodology accepted by the scientific community, was not based on a reasonable degree of scientific certainty, and would not assist the trier of fact in understanding the evidence or facts. Significantly, the trial court noted that Dr. Milby purportedly relied on a report by the University of Minnesota (Minnesota Report) that found a statistically higher occurrence of brain cancer among individuals who worked at the Spring House facility. That report finding, however, ultimately was inconclusive as to the cause of brain cancer in the Spring House workers and the causal relationship between chemicals at the Spring House facility and the increased incidence of brain cancer—a critical fact that Dr. Milby ignored in reaching his contrary conclusion as to the decedent. Because Dr. Milby's opinion contained no evidence that the decedent's brain cancer was caused by chemicals at the Spring House facility and was not based on any scientific methodology supporting his conclusion, the trial court granted Rohm and Haas's Frye motion. The trial court also granted summary judgment for Rohm and Haas because the plaintiff could not offer any other evidence to prove causation. The plaintiff appealed.

In affirming the trial court's ruling excluding Dr. Milby's opinion, the Pennsylvania Superior Court concluded that the opinion "failed to meet the basic admissibility requirements for expert testimony" under Rule 702. Snizavich, 83 A.3d at 197–98. Specifically, to be admissible as expert opinion under Pennsylvania law, the proffered testimony:

must point to, rely on or cite some scientific authority—whether facts, empirical studies, or the expert's own research—that the expert has applied to the facts at hand and which supports the expert's ultimate conclusion. When an expert opinion fails to include such authority, the trial court has no choice but to conclude that the expert opinion reflects nothing more than mere personal belief. Thus, expert testimony as to a causal relationship may be admissible, even if based solely on the expert's review of medical records and his experience and expertise in the applicable medical field, when the expert can point to some scientific authority that supports the causal connection.

Snizavich, 83 A.3d at 197 (emphasis added). The superior court reasoned that Dr. Milby's opinion that the chemicals at the Spring House facility caused the decedent's brain cancer lacked any scientific basis or authority—i.e., any facts, testimony, or empirical data—supporting his conclusion regarding the alleged causal relationship between exposure to chemicals at the Spring House facility and brain cancer. Instead, Dr. Milby offered an opinion based solely on documents relating to the decedent's medical and work histories and work conditions, the Minnesota Report (which was inconclusive as to the causal relationship between the Spring House facility chemicals and brain cancer and contradicted Dr. Milby's opinion), and his subjective beliefs, knowledge, and experience in the fields of epidemiology, toxicology, and occupational medicine. Because Dr. Milby did not rely on any medical or scientific literature that actually found a causal relationship between exposure to chemicals at the Spring House facility and brain cancer, and did not provide any reason to doubt the scientific veracity of the Minnesota Report, the Superior Court concluded that Dr. Milby's opinion was nothing more than lay opinion offered by an expert and therefore was inadmissible.

The superior court's decision in Snizavich reaffirms the minimum standard under Pennsylvania law that proffered testimony must meet to qualify as expert opinion and be admissible. Critically, the decision also heightens, or at least reinforces, the burden of plaintiffs in toxic tort cases to proffer expert testimony with a sufficient scientific basis, applied to the facts of the case, to establish the requisite causal link between the alleged injury and exposure to the defendant's product. This burden will be particularly difficult for plaintiffs to meet where, as in Snizavich, the scientific and medical literature has not found a conclusive nexus between a given product and the alleged injury. Defendants in toxic tort cases therefore have another weapon in their arsenal to refute liability.

Keywords: litigation, expert witnesses, expert testimony, toxic tort, causation, Rule 702, Frye, scientific authority

John J. DiChello is with Blank Rome LLP in Philadelphia, Pennsylvania. 

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