In re Roundup Products Liability Litigation

Numerous patients (plaintiffs) suffering from Non-Hodgkin lymphoma (NHL) sued Monsanto Company (defendant). The patients claimed that glyphosate, an herbicide produced by Monsanto, caused their NHL. In the general-causation phase of the trial, the patients offered expert evidence to support their claim that glyphosate could cause NHL. In the next phase, three patients (bellwether patients) were selected to establish specific causation, that is, to show that glyphosate did cause the bellwether patients’ NHL. The bellwether patients’ medical experts used differential diagnosis to show that each bellwether patient’s NHL was caused by glyphosate. That is, the experts ruled out other possible causes of the bellwether patient’s NHL and then explained why glyphosate should be ruled in as the most likely cause. Each bellwether patient had often used glyphosate. There were no biological differences between NHL cases caused by glyphosate and NHL cases arising from other causes. For each bellwether patient, the experts relied on the general-causation experts’ evidence that glyphosate could cause NHL, the absence of other risk factors, and the bellwether patient’s significant glyphosate exposure to support the conclusion that glyphosate was a substantial factor in the bellwether patient’s NHL. The experts also stated that the bellwether patients’ risk factors were increased by their extensive exposure to glyphosate. Monsanto filed a motion for summary judgment, arguing that the experts’ methods were unreliable. Monsanto argued that the experts had to show that the bellwether patients’ NHL was not caused by unknown factors.