McCostlin v. Monsanto Company: Missouri Court of Appeals Clarifies Causation Requirement in Toxic Tort Cases

The Missouri Court of Appeals for the Eastern District, in McCostlin v. Monsanto Company, affirmed the trial court’s directed verdict in favor of Monsanto Company, finding the plaintiffs’ experts failed to provide testimony sufficient to prove that plaintiffs’ injuries were caused by exposure to Monsanto’s products.

The appeal stems from a petition on behalf of 87 individual plaintiffs, alleging they had been diagnosed with non-Hodgkin’s Lymphoma (“NHL”) after being exposed to Monsanto’s Roundup (or similar) products. Trial began on behalf of one injured plaintiff, Mark McCostlin, and his wife.

The McCostlins put forward two experts at trial: a toxicologist and a clinical oncologist. During his deposition, the toxicologist opined Mr. McCostlin experienced somewhere between 13 and 33 cumulative exposure days to Roundup during his life. This estimation was based on Mr. McCostlin’s deposition testimony regarding his use of Roundup. Based on that estimation, the oncologist testified at his deposition that Mr. McCostlin’s NHL “was caused by exposure to Roundup.”

However, at trial Mr. McCostlin changed his testimony regarding his use of Roundup, now testifying that he used Roundup significantly less than his deposition testimony. After a motion from Monsanto, the toxicologist revised his calculations and found Mr. McCostlin had only 9.59 exposure days to Roundup. Considering this new exposure level, the oncologist could only testify that Mr. McCostlin’s use of Roundup “may have contributed to the risk” of him developing NHL. (The toxicologist was precluded from offering an opinion as to whether or not Mr. McCostlin’s exposure to Roundup caused his NHL.)

After the plaintiffs’ trial-in-chief, Monsanto moved for a directed verdict, while the plaintiffs moved to recall the oncologist to clarify his testimony. The judge granted Monsanto’s motion for directed verdict and denied the plaintiffs’ motion to recall the oncologist. The McCostlins appealed on multiple grounds, but the appeals court affirmed the trial court’s verdict.

As motions for directed verdict are reviewed de novo, the Court thoroughly examined the oncologist’s testimony and the Missouri standard for causation in toxic tort cases. Under Missouri law, a plaintiff must establish both general and specific causation in toxic court cases. General causation refers to whether an injury can be caused by a certain process. Specific causation, on the other hand, refers to whether the specific plaintiff’s injury was caused by the process at issue. Looking at the oncologist’s testimony, the Court found he never testified Mr. McCostlin’s exposure to Roundup caused or contributed to cause his NHL. Instead, he could only provide testimony that his exposure contributed to his risk of developing NHL. The Court of Appeals found this testimony was an “assurance of a possibility” and therefore “not sufficient to establish causation.” And because the oncologist was the only potential causation expert, the Court found the McCostlins had failed to put forth any evidence of specific causation and had therefore failed to meet their burden of proof. Therefore, a directed verdict was proper.

The Court also found the trial court properly denied the plaintiffs’ motion to recall the oncologist, whose testimony was uncontradicted and consistent. He repeatedly testified that Mr. McCostlin’s exposure to Roundup only put him at an elevated risk for contracting NHL, not that his exposure to Roundup caused or contributed to cause his NHL. Motions to recall witnesses are used to correct erroneous statements. As the oncologist was clear he was testifying about risk and not causation, there was no erroneous statement for him to correct and the motion to recall him was properly denied.