The science of glyphosate – the court’s view

The science of glyphosate – the court’s view

The science of glyphosate – the court’s view 700 350 Adam Grossman

This summer saw two major developments in glyphosate litigation: a California jury finding in favor of a plaintiff claiming glyphosate caused his non-Hodgkin lymphoma, and a federal judge deciding that the 6000-plus plaintiffs in the coordinated glyphosate proceedings could proceed past the general causation stage.

At the time of writing, Praedicat’s General Causation score for glyphosate and blood cancer is 0.27 (where -1 means the hypothesis is rejected and +1 means it is indisputably accepted). We’d classify the 0.27 level as insufficient to sustain mass litigation – most commonly because literatures with that score are frequently dominated by animal studies that cannot establish general causation without corroborating epidemiological evidence. Glyphosate is among the exceptions where the current score reflects a literature with conflicting human studies: four showing no effect and five showing an effect, and the studies showing an effect vary in the size of the effect. This creates a state of true scientific debate as to whether glyphosate can cause cancer. The judge’s decision leaves it to the jury to decide how to resolve this debate.

Is it appropriate for the judge to allow dueling expert witnesses to attempt to win over the jury with their own methods of weighing the scientific evidence? After all, the jury is the finder of fact, and the job of expert witnesses according to Daubert is to assist the finder of fact in making its factual determinations. But should the existence of legitimate debate over glyphosate’s potential to cause non-Hodgkin lymphoma suffice to let a jury hold Monsanto responsible for people’s illnesses?

Indeed, this scientific debate as to glyphosate’s role in cancer causation featured prominently in the judge’s opinion that allowed several of the plaintiffs’ experts to testify. While most opinions regarding expert testimony are fairly cut and dried, yielding a near complete win for either the plaintiffs or defendants, this one was a mixed bag. Monsanto’s experts will be allowed to testify as to the lack of general causation, but most of the plaintiffs’ experts will also be allowed to give opinions that general causation has been met. The judge summed up the decision quite neatly in its opening paragraphs:

The question at this early phase in the proceedings – the “general causation” phase – is whether a reasonable jury could conclude that glyphosate…can cause NHL at exposure levels people realistically may have experienced. If the answer is yes, [we then assess] whether each particular plaintiff’s NHL was caused by glyphosate. If the answer is no, none of the plaintiff’s cases may proceed. …

The second problem with the plaintiff’s presentation is that the evidence of a causal link between glyphosate exposure and NHL…seems rather weak. Some epidemiological studies suggest that glyphosate is slightly or moderately associated with increased odds of developing NHL. Other studies, including the largest and most recent, suggest there is no link at all…. The evidence, viewed in its totality, seems too equivocal to support any firm conclusion that glyphosate causes NHL…. However, the question at this phase is not whether the plaintiffs’ experts are right. The question is whether they have offered opinions that would be admissible at a jury trial.

The difference between the plaintiff and defense experts is not about which studies are important – quite the contrary. The only real difference is about how to weigh the evidence present in the literature. In effect, then, the judge is allowing for the possibility that multiple General Causation scores can coexist, simply by virtue of different literature weightings. The jury gets to decide which weighting scheme they prefer, according to this judge. It is hard to imagine how they will make this assessment.

At Praedicat we believe that a single objective view, applied across multiple literatures, can help sort out how the scientific information adds up to reach a preliminary conclusion. Using this approach, we can point to many other risks, including other herbicides, with higher general causation scores for some harm that nonetheless appear to be widely used in commerce. The judge even agrees that the evidence for glyphosate is weak, even if none of the experts strayed so far from the data in drawing their conclusions to preclude their testimony. I am left wondering if an appeals court will use the words in the opinion itself to reverse this evidentiary decision and grant summary judgement in favor of Monsanto.

We may never find out what an appeals court says, however. Throughout the opinion, the judge continually reinforced that general causation is only the first step, and it is entirely possible (maybe the judge even thinks it likely) that no plaintiff could satisfy the specific causation hurdle. If nobody can get over that hurdle, Monsanto will win in the end, but having spent a lot more money to defend these claims compared to winning at the general causation stage.