The Volokh Conspiracy

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The Crazy Verdicts Against Bayer/Monsanto in the Roundup Litigation


On Monday, a California jury ruled against Monsanto in a case alleged that the herbicide Roundup caused a couple's non-Hodgkin's lymphoma. The jury awarded $55 million in compensatory damages, and an additional $2 billion in punitive damages. This was Monsanto's third straight loss before a jury in a Roundup case.

To say that these verdicts are  not justified by the scientific evidence would be a massive understatement. Every regulatory body in the world that has studied Roundup has declared that it's safe and that it's unlikely that it's a carcinogen. The only partial exception is that the International Agency for Research on Cancer has declared that the active ingredient in Roundup is a probable carcinogen based on animal studies–but at an undetermined dose through undetermined means of exposure. Regulatory agencies that have revisited Roundup's safety in the wake of the IARC report have reaffirmed its safety, in part based on new studies not considered by the IARC.

Just how weak is the evidence presented by plaintiffs that Roundup caused their NHL? Here is the judge in a previous California case explaining why, in his opinion, the jury's verdict was justified based on the relevant scientific evidence.

Plaintiff's evidence that his NHL was caused by his exposure to GBHs was based on the testimony of Dr. Nabhan, a former practicing oncologist. Dr. Nabhan does not dispute that he is unable to identify a cause of NHL in the majority of his patients. Tr. 2990:6-14; 2997-2998. Nonetheless, Dr. Nabhan opined that Mr. Johnson's cancer was not idiopathic and that there was substantial evidence that his NHL was caused by his exposure to GBHs: a "known carcinogen causing non-Hodgkin's lymphoma." Tr. 2997:5-10.
Dr. Nabhan elected to conduct a type of causation analysis known as a differential diagnosis, or differential etiology, in reaching the opinion that GBHs caused Plaintiff's NHL. Differential diagnosis is a process whereby the physician begins by 'ruling in' all possible causes of the plaintiff's illness then 'rules out' the least plausible causes until the most likely cause remains. The final result of a differential diagnosis forms the basis of the physician's conclusion regarding what caused the plaintiff's illness. Cooper v. Takeda Pharms. Am., Inc. (2015) 239 Cal. App. 4th 555, 565-66.
In performing his differential diagnosis, Dr. Nabhan explained that because Mr. Johnson was much younger than the average patient who developed the disease this raised a "red flag" that his cancer is not likely to be idiopathic and more likely to be caused by an exposure. Tr. 2842:23¬2844:19. Dr. Nabhan considered the known risk factors and causes of NHL including age, race, immunosuppressant therapies, autoimmune diseases, skin conditions, occupation, occupational exposures and viruses. Id. at 2842-2852. Dr. Nabhan opined that sun exposure, tobacco, and alcohol are not known causes of NHL and could therefore be excluded. Id. at 2852-2853. After conducting his differential diagnosis, Dr. Nabhan concluded that Mr. Johnson's only known risk factors were his race (African American) and exposure to GBHs. Tr. 2853:19-23. Dr. Nabhan therefore concluded that the GBHs were the most substantial contributing factor to Mr. Johnson's NHL. Id. at 2853:24-2854:2.

This isn't science, it's witchcraft, and the testimony should have been excluded entirely under the Sargon precedent in California, which bars courts from admitting "speculative" expert testimony. To call Nabhan's causation testimony "speculative" would be generous. And note again that the above excerpt is the judge explaining why the testimony was sufficient to support a verdict, not a hostile account of Nabhan's testimony.

UPDATE: I neglected this gem a couple of paragraphs down: "Because there is no substantial evidence of an alternative explanation for Plaintiffs NHL, the jury here was free to give weight to Dr. Nabhan's testimony that GBHs were a substantial factor in causing the cancer." Given that everyone acknowledges that most cases of NHL are idiopathic, that is just incoherent.

I'm doing a teleforum on the Roundup litigation for the Federalist Society today at 2 pm.

CONFLICT OF INTEREST WATCH: Other than academic interest, I have no stake in any way in this litigation and no affiliation with Monsanto or its attorneys.