Federal Judge Rejects Key Expert Witness in Paraquat Lawsuits, Dismissing Initial Cases

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Federal Judge Deals Blow to Paraquat Lawsuits, Dismissing Initial Cases

In a significant development in the ongoing paraquat lawsuits, a federal judge has dismissed the first four cases set for trial. U.S. District Judge Nancy Rosenstengel ruled on Wednesday that a key expert witness, Cornell University professor Martin Wells, cannot testify in court. Without Wells’ testimony, the trials cannot proceed.

5 Key Points

  • Judge Rosenstengel barred Professor Martin Wells from testifying, stating that his analysis relied on “unscientific cherry-picking” and lacked peer-reviewed validation.
  • The ruling directly impacts the first four cases set for trial but does not apply to the more than 5,000 other cases centralized in the East St. Louis, Illinois court.
  • Plaintiffs’ lawyers plan to appeal the decision and propose a new set of cases for trial.
  • Syngenta and Chevron deny that paraquat causes Parkinson’s disease, citing scientific consensus and decades of peer-reviewed literature.
  • Several hundred paraquat cases are also pending in state courts, with the first trials potentially happening later this year.

Judge’s Ruling on Expert Witness

Judge Rosenstengel’s decision to bar professor Martin Wells from testifying dealt a significant blow to the plaintiffs’ cases. She criticized Wells’ analysis, stating that it relied on “unscientific cherry-picking” and that it was a “red flag” that his view had not been adopted or independently validated in any peer-reviewed scientific analysis outside of the litigation.

Impact on Other Paraquat Lawsuits

While the ruling directly impacts the first four cases set for trial, it does not apply to the more than 5,000 other cases centralized in Judge Rosenstengel’s court. The judge has ordered the plaintiffs’ lawyers and the companies to propose another set of cases for trial, giving the plaintiffs an opportunity to offer a new expert witness.

Plaintiffs’ Lawyers to Appeal Decision

The lead attorneys for the plaintiffs – Khaldoun Baghdadi, Sarah Doles, and Peter Flowers – have expressed their disagreement with the ruling and intend to appeal the decision. They remain committed to prosecuting these cases on behalf of the thousands of American farmworkers diagnosed with Parkinson’s disease due to their exposure to paraquat.

Companies Deny Paraquat Causes Parkinson’s Disease

Syngenta and Chevron have consistently denied that paraquat causes Parkinson’s disease. Chevron stated that the decision affirms the scientific consensus that paraquat has not been shown to cause Parkinson’s disease, despite hundreds of studies conducted over the past 60 years. Syngenta expressed its satisfaction with the ruling, calling it “consistent with decades of peer-reviewed scientific literature.”

The Future of Paraquat Litigation

The dismissal of the first four paraquat lawsuits set for trial marks a significant setback for the plaintiffs. However, with thousands of cases still pending and the plaintiffs’ lawyers determined to appeal the decision, the legal battle over the alleged link between paraquat and Parkinson’s disease is far from over. As the litigation progresses, both sides will continue to present their arguments and evidence, with the ultimate goal of determining whether paraquat exposure can be held responsible for the development of Parkinson’s disease in agricultural workers.


Q. What is paraquat, and how is it used?

A. Paraquat is an herbicide that has been on the market since the mid-1960s. It is approved by the U.S. Environmental Protection Agency only for licensed users, often on large commercial farms.

Q. Why are agricultural workers suing Syngenta and Chevron over paraquat?

A. Agricultural workers are suing Syngenta and Chevron, claiming that occupational exposure to paraquat can cause Parkinson’s disease.

Q. How many paraquat lawsuits are currently pending?

A. There are more than 5,000 paraquat lawsuits centralized in the U.S. District Court for the Southern District of Illinois, with several hundred additional cases pending in state courts, primarily in California.

Q. What is the significance of Judge Rosenstengel’s ruling on the expert witness?

A. Judge Rosenstengel’s ruling barring professor Martin Wells from testifying dealt a significant blow to the plaintiffs’ cases, as his testimony was crucial to establishing a link between paraquat exposure and Parkinson’s disease.

Q. What is the current status of paraquat use worldwide?

A. Although paraquat remains approved for use in the United States, it has been banned in more than 60 countries worldwide. Its popularity in the U.S. is partly due to weeds becoming resistant to other herbicides like Bayer’s Roundup.


Pierson, B. (2024, April 17). Judge rejects key expert in paraquat lawsuitstosses first cases set for trial. Reuters. https://www.reuters.com/legal/litigation/judge-rejects-key-expert-paraquat-lawsuits-tosses-first-cases-set-trial-2024-04-17/

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