Syngenta, Chevron Ask Judge to Toss Paraquat Parkinson’s Disease Lawsuits

Defendants argue that plaintiffs' Paraquat Parkinson's disease lawsuits hinge on one expert witness whose scientific methodology they question.

As a number of Paraquat lawsuits move forward in the federal court system, Syngenta and Chevron are joining together in filing a motion for summary judgment, asking a U.S. District Judge to dismiss the litigation based on what they say is a lack of evidence that Paraquat causes Parkinson’s disease.

The two companies face more than 3,800 product liability lawsuits brought by former farmers and others in the agricultural industry, each raising similar allegations that the manufacturers failed to warn about the link between Paraquat and Parkinson’s disease, which they maintain can develop after regularly spraying, mixing, transporting or handling the widely used weed killer. However Syngenta and Chevron also face a number of lawsuits involving Paraquat “drift”, where plaintiffs were exposed to the weed killer from nearby spraying.

Given common questions of fact and law raised in the cases, all complaints brought throughout the federal court system have been centralized as part of a Paraquat MDL since June 2021, with U.S. District Judge Nancy J. Rosenstengel presiding over coordinated discovery and pretrial proceedings in the Southern District of Illinois.

PARAQUAT Parkinson's Lawsuits

Did you get Parkinson's after exposure to Paraquat?

Exposure to the toxic herbicide Paraquat has been linked to a risk of Parkinson's disease.


To help the parties evaluate how juries may respond to certain evidence and testimony that will be repeated throughout various claims, the Court previously established a bellwether schedule, which calls for a small group of Paraquat lawsuits to be prepared for trial, which are now expected to begin in early 2024.

Defendants Motion to Dismiss Paraquat Parkinson’s Disease Lawsuits

On June 9, Syngenta and Chevron filed a roadmap brief (PDF) in support of their motion for summary judgment, which will seek to have the cases dismissed due to a lack of evidence of causation.

The roadmap brief claims plaintiffs are relying on a single expert witness who will link Paraquat to Parkinson’s disease risk, and the manufacturers are questioning that plaintiffs’ scientific methodology. It claims that the scientific consensus is that Paraquat is not linked to Parkinson’s disease risks, which plaintiffs dispute.

“At bottom, Plaintiffs’ experts offer causation opinions that they have never submitted to the rigors of peer review and publication, that run counter to the scientific concensus, and that contradict their own out-of-court publications. In doing so, they fail to employ the same level of scientific rigor they use outside of court and instead rest on unreliable analyses, speculative extrapolation from flawed evidence, and blind adoption of lawyer-fed assumptions,” according to the defendant’s brief. “This is precisely the kind of unreliable litigation-science the court must guard against as gatekeeper.”

Lawyers representing plaintiffs in the Paraquat litigation have not yet filed their response, but have pointed in prior filings to a growing body of scientific evidence that establishes exposure to Paraquat causes Parkinson’s disease, maintaining that thousands of individuals may have avoided the devastating diagnosis if adequate warnings and instructions had been provided.

2023 Paraquat Parkinson’s Lawsuit Update

Over the coming months, a series of Daubert hearings for Paraquat lawsuits will be held, at which time the Court will consider challenges presented by each side that seek to exclude certain expert witnesses or opinions that may be offered at trial about the link between exposure to Paraquat and Parkinson’s disease. The court will consider the qualifications of each experts, the basis for their opinions and determine whether the proposed testimony will be permitted at trial.

To prevail in the motion for summary judgment, the manufacturers must convince the court to exclude the plaintiff’s expert witnesses establishing that Paraquat causes Parkinson’s disease, which would likely face a lengthy appeals process.

If the court rejects this motion for summary judgment, it is expected that a series of bellwether trials will be held next year, to determine how the evidence holds up at trial and what average Paraquat lawsuit payouts will be awarded by juries.

While the outcome of these trials will not have any binding impact on other plaintiffs, they are expected to greatly influence the average Paraquat settlement amounts the manufacturers may offer to avoid each individual claim being remanded back to U.S. District Courts nationwide for separate trial dates in the coming years.


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