Psuedo-science is not expert testimony
The courtroom has increasingly become a battleground—not just for legal expertise but also for scientific credibility. Recent cases across the United States have highlighted a significant and troubling issue in litigation: the extent to which expert witness testimony is actually of questionable, or even completely negligible, scientific value. Cherry-picked evidence and junk science not only risk unfairly skewing legal outcomes but also undermine public trust in both the judiciary and the scientific establishment.
Just recently, in mid-April, Judge Nancy Rosenstengel, the U.S. District Judge presiding over a massive body of litigation concerned with whether the common herbicide paraquat can cause Parkinson’s disease, excluded Cornell epidemiologist Martin Wells from testifying in four bellwether trials, due to substantial discrepancies in his testimony. Given the importance of Wells’ testimony to the plaintiffs’ cases—he was, in fact, the only witness to have purportedly established that paraquat has a causal link to Parkinson’s—his disqualification speaks volumes about not only the scientific quality of his testimony but calls into question the veracity of the plaintiffs’ cases overall.
The dismissal of these four initial cases following Wells’ disqualification casts significant uncertainty over the fate of the more than 5,000 paraquat lawsuits centralized under Judge Rosenstengel’s jurisdiction. Paraquat, highly toxic yet highly effective, has been repeatedly approved by the U.S. Environmental Protection Agency (EPA) under the condition that it only be used by trained and certified farmers wearing protective gear. While the EPA argued in its latest review that the benefits of the chemical outweigh any potential risks after examining a substantial body of scientific literature, Martin Wells largely focused on nine studies, only one of which was found to be “high quality” by the EPA; “his proffered opinion,” Judge Rosenstengel determined, “required several methodological contortions and outright violations of the scientific standards he professed to apply.”
Judge Rosenstengel’s decision to disqualify Dr. Wells represents growing judicial awareness about the questionable quality of some expert evidence, especially in cases where large settlements and significant public health concerns are involved.
Last November, another prominent case collapsed over unreliable scientific expertise. U.S. District Judge Denise Cote found that none of the five expert witnesses in a case alleging that painkiller Tylenol could cause autism had based their views on sound scientific methodology. In her 148-page ruling, she explained that “the unstructured approach adopted by the plaintiffs’ experts permitted cherry-picking, allowed a results-driven analysis, and obscured the complexities, inconsistencies, and weaknesses in the underlying data.”
Underscoring the importance of a cautious approach, Judge Cote noted that “the issues explored by this litigation have great public health significance. It matters to get this right”—particularly given that Tylenol is currently one of the only pain relievers that doctors believe is safe for pregnant women.
Unfortunately, in some cases, weak evidence masquerading as expert testimony ends up going before the jury and influencing their decisions. A $223 million ruling against Johnson & Johnson was overturned in October 2023 because the jury had been allowed to hear “improper scientific testimony” linking J&J’s talc-based products to cancer.
But why is “junk science” making its way so frequently into the courts? Some experts believe the adversarial nature of legal proceedings could naturally polarize scientific testimony. David Eastmond, a retired environmental scientist who briefly worked as an expert witness, noted that the process of working closely with lawyers could bias experts to present evidence in a way that supports the client’s case rather than in an unbiased manner. “The more you study and construct arguments and think through your arguments, it reinforces the position you’ve taken,” Eastmond remarked. “Attorneys, by their nature, want to polarize things, so that things become more black-and-white. And in my experience, things are sort of gray.”
The lucrative nature of being an expert witness could also play a role in encouraging dubious science—just look at Bennet Omalu, who casts himself as a heroic expert bravely fighting corporate interests. Despite wild and erroneous interpretations of scientific studies, Omalu has turned serving as an expert witness into essentially his whole career, earning $900,000 in a single year from his flawed scientific testimony.
The ramifications of this proliferation of sub-par “expert” testimony in litigation are significant. When courts allow juries to hear scientifically dubious evidence, they not only undermine public trust in the legal process but also in the scientific community. The consequences can be dire, particularly in cases involving serious public health and safety matters. As such, there is a pressing need for stricter standards in the admissibility of scientific evidence in litigation—a need that courts are increasingly recognizing but are still far from fully addressing.
As we move forward, it is crucial for the legal system to adopt more rigorous methodologies for evaluating scientific claims, perhaps drawing on the model used in peer-reviewed scientific research. This would ensure that only evidence that withstands rigorous scrutiny can influence jury decisions and court outcomes, thereby upholding the integrity of both science and the law in public policy.
