Differentiating Between Junk Science and Admissible Expert Opinion in Pennsylvania

In environmental personal injury cases, proof of causation is key and that causation almost always hinges on expert opinion.  A recent appellate decision in Pennsylvania in Snizavich v. Rohm and Haas Company provides useful clarification about the line between junk science and admissible expert opinion.

In Snizavich, the wife of a deceased worker at a chemical plant alleged that her husband had died because exposure to hazardous chemicals in the workplace had precipitated  his brain cancer.  Faced with a summary judgment motion alleging that there was no basis for asserting that exposure to chemicals had caused the husband’s brain cancer, the wife proffered the opinion of  a medical doctor who said that in his opinion to a reasonable certainty there was a causal link between the exposure to workplace chemicals and the husband’s brain cancer.  While noting that the opinion was presented by a scientist who used the “magic words” of an expert opinion, the court refused to admit it.  As both the trial court and the appellate court found, the opinion was not rooted in any scientific basis other than subjective belief.   Although the expert had cited to a scientific study as the basis of his opinion, the conclusion of that study specifically stated that it had not found a causal link between exposure to the chemicals and brain cancer.  Hence, the court ruled that there was no scientific basis undergirding the expert’s opinion.

According to the Pennsylvania court, an opinion offered by a scientist is not an admissible expert opinion unless the opinion is supported by documented scientific authority.  It is not enough that the opinion is offered by a scientist who relies on his own observations and experience in the field; the opinion must be based on outside sources of scientific authority.  It is reassuring to see a trial court take seriously its gatekeeping function to exclude unreliable expert opinion and then have that decision affirmed by the appellate court.

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