Hann v. Monsanto Co.

Background

Adrine Hann alleged that Roundup caused her multiple myeloma. She brought claims involving design defect, failure to warn, negligence, and breach of implied warranty. Hann’s counsel conceded that expert testimony was required for the design-defect claim, but argued that expert testimony was not necessary for the failure-to-warn, negligence, and implied-warranty claims because multiple myeloma is caused only by environmental factors. The opinion states that Hann was otherwise healthy, had no family history of cancer, and developed multiple myeloma sometime after she began using Roundup.

Court’s reasoning

The court applied Michigan law. It explained that Michigan generally requires expert testimony when a case involves highly technical and scientific questions, although the Michigan Supreme Court had not decided whether expert causation testimony is always required in toxic-tort cases. The court determined that whether Roundup caused Hann’s multiple myeloma was such a technical and scientific question. Without a specific-causation expert—an expert who could address whether Roundup caused Hann’s illness—a jury could only speculate.

Ruling and effect

Judge Vince Chhabria granted summary judgment in favor of Monsanto because Hann failed to disclose a specific-causation expert. The order states that Monsanto was entitled to summary judgment under Michigan law.