Roundup Design Defect Trial Opens in St. Louis County, the First Test for Monsanto After Durnell

The first Roundup design defect trial after Durnell is underway

The first Roundup design defect trial since the Supreme Court cut off cancer-warning claims opened on Tuesday, September 29, 2026, when a St. Louis County jury heard opening statements in Aretino, et al. v. Monsanto Co., No. 20SL-CC03676, before Judge Brian May. Three women who developed non-Hodgkin lymphoma after years of using Roundup, and who refused Bayer's $7.25 billion class settlement, are asking the jury to find that glyphosate-based Roundup was defectively designed and inadequately tested, a theory the Supreme Court did not decide in Monsanto Co. v. Durnell and that Monsanto insists is preempted anyway.

That framing is what makes this the most closely watched Mass Tort trial of the fall. For eight years, Roundup juries heard cases built around one proposition: Monsanto should have put a cancer warning on the label. Durnell took that proposition off the table in June. Aretino is the first time a jury will decide whether the litigation can survive on the theory that the product itself, not the label, was the problem. Whatever the jury does, the result will be read by Bayer's investors, by the judge weighing the class settlement across town, by Judge Vince Chhabria in the federal Multidistrict Litigation (MDL), and by every plaintiffs' firm deciding whether the roughly 65,000 remaining Roundup claims are worth trying or worth folding into the settlement matrix.

The trial is expected to run four to five weeks, according to Courtroom View Network, which is webcasting the proceedings. That puts a verdict somewhere in late October or early November 2026, assuming the case reaches the jury.

What is the first Roundup trial after Monsanto v. Durnell?

The first Roundup trial after Monsanto v. Durnell is Aretino v. Monsanto, a three-plaintiff Roundup design defect trial in the Circuit Court of St. Louis County, Missouri (the 21st Judicial Circuit), before Judge Brian May, with opening statements held September 29, 2026. It is the first jury trial anywhere in the country to test Roundup claims built entirely on Design Defect and testing theories rather than Failure to Warn.

Two details about the forum matter more than they seem.

First, this is St. Louis County, not the City of St. Louis. Missouri treats them as separate jurisdictions with separate circuit courts. The City of St. Louis is the 22nd Judicial Circuit, where Judge Timothy Boyer is deciding whether to approve the $7.25 billion King v. Monsanto class settlement and where the original Durnell verdict was returned in 2023. St. Louis County, which surrounds the city, is the 21st Judicial Circuit. Several wire reports have described the Aretino judge simply as "a St. Louis judge"; the docket prefix "20SL-CC" and Judge May's assignment place the case in the county court.

Second, the "20" in the case number means the case was filed in 2020. These plaintiffs have been in the pipeline for six years, through the 2020 Bayer inventory settlements, the 2023-2024 run of large Missouri and Pennsylvania verdicts, and the 2026 class deal. Their decision to opt out was made before the Supreme Court ruled. They are now trying the only claims Durnell left them.

Who are the plaintiffs in the Aretino v. Monsanto Roundup trial?

The plaintiffs are Theresa Aretino, Cynthia Fernandez and Betty Larkin. All three used Roundup regularly and later developed non-Hodgkin lymphoma, the blood cancer that has been the focus of virtually all glyphosate litigation. Fernandez died before the trial began, so her claim is being pursued on her behalf. All three declined to participate in the proposed $7.25 billion class settlement, which is why they are in a courtroom rather than a claims queue.

Their lead trial lawyer is Greg Dovel. Monsanto is defended at trial by Paul Boehm of Sidley Austin, a product liability trial lawyer who joined Sidley's Washington office from Williams & Connolly in late 2025.

The joinder of three plaintiffs is itself significant. Multi-plaintiff Roundup trials have produced some of the largest verdicts in the litigation's history, most prominently the four-plaintiff Anderson trial in Cole County, Missouri, in which a jury awarded $1.56 billion in November 2023. A combined trial lets the plaintiffs present the corporate-conduct evidence once while multiplying the damages exposure, and it lets the jury see several injured people rather than one.

What did the Supreme Court decide in Monsanto v. Durnell?

In Monsanto Co. v. Durnell, decided June 25, 2026, the Supreme Court held 7-2 that the Federal Insecticide, Fungicide, and Rodenticide Act expressly preempts a state-law failure-to-warn claim contending that a pesticide label should have carried a cancer warning in addition to, or different from, the label the Environmental Protection Agency approved. Justice Kavanaugh wrote for the Court; Justice Jackson dissented, joined by Justice Gorsuch.

The case arose from a $1.25 million verdict that John Durnell won in the Circuit Court of the City of St. Louis in October 2023. The jury found for Durnell only on his failure-to-warn claim, rejected his other theories, and declined to award Punitive Damages. The Missouri Court of Appeals, Eastern District, affirmed in February 2025. The Supreme Court granted certiorari on January 16, 2026, heard argument in April, and reversed.

The operative text is FIFRA's preemption clause, 7 U.S.C. § 136v(b), which bars states from imposing "any requirements for labeling or packaging in addition to or different from those required under" FIFRA. Because federal law requires a registrant to use the label EPA approved, the Court reasoned, a state jury verdict premised on the label needing a different cancer warning imposes exactly the kind of "different" labeling requirement the statute forbids. Bayer said after the ruling that it expected the decision to "significantly contain" the litigation.

Justice Jackson's dissent argued that the majority misread FIFRA's requirements and the scope of its preemption clause, and that the ruling "leaves Durnell without a remedy for the significant harms he has suffered."

What Durnell did not do is equally important. The question presented, and the holding, concern failure-to-warn claims. The Court did not hold that FIFRA preempts claims that a pesticide was defectively designed, defectively manufactured, or negligently tested. That gap is the entire legal foundation of the Aretino trial.

Are Roundup design defect claims preempted after Durnell?

Not according to the only Missouri trial court to rule in writing so far, and not under the Supreme Court's own precedent, but Monsanto argues they are, and the question is certain to reach appellate courts. The answer, for now, is that Roundup design defect claims are going to trial in Missouri while Monsanto preserves the preemption argument for appeal.

The Bates v. Dow Agrosciences baseline

The plaintiffs' anchor is Bates v. Dow Agrosciences LLC, 544 U.S. 431 (2005), in which Texas peanut farmers sued over crop damage from a Dow herbicide. The Supreme Court held that § 136v(b) reaches only state requirements "for labeling or packaging." It then said, in language every Roundup plaintiff now quotes, that rules requiring manufacturers to design reasonably safe products, to market products free of manufacturing defects, and to honor express warranties "plainly do not qualify" as labeling or packaging requirements, because none of them requires a manufacturer to label or package a product in any particular way. Bates also rejected an "inducement" test under which any claim that might pressure a manufacturer to change its label would be preempted.

Durnell applied Bates' parallel-requirements framework to warnings and found the cancer-warning claim preempted. It did not overrule Bates' treatment of design claims. On that reading, a claim that glyphosate formulations were unreasonably dangerous as designed, or that Monsanto failed to conduct the testing a reasonable manufacturer would have done, survives because the remedy it demands is a different product or a different research program, not a different label.

Monsanto's position: repackaged warning claims and implied preemption

Monsanto's answer has two parts. The first is that many Roundup "design" claims are warning claims in disguise. If the alleged defect is that users were not told about a cancer risk, relabeling the theory as design does not change its substance, and Durnell forecloses it. The second is implied preemption: glyphosate formulations are registered with EPA as specific products, so a state-law duty to sell a different formulation would conflict with the federal registration scheme or, in a version of the impossibility argument familiar from pharmaceutical cases, would require Monsanto to sell something EPA had not approved.

According to Courtroom View Network's preview, Monsanto maintains that the Aretino design defect claims are preempted under Durnell, and any verdict for the plaintiffs is expected to be appealed through both the Missouri appellate courts and, potentially, back to the U.S. Supreme Court.

The Shull ruling in Boone County

The first written test of those arguments came a month before Aretino. On August 31, 2026, Boone County Circuit Judge Jeff Harris denied Monsanto's motion for summary judgment in Marvin "Kent" Shull's Roundup case, in what Missouri Lawyers Media described as possibly the first ruling in the country on the scope of Durnell. Judge Harris held that Durnell addressed failure-to-warn claims and did not extend to Shull's design defect and negligence claims. He rejected Monsanto's implied-preemption argument, reasoning that FIFRA's registration procedure does not bar design and negligence claims because manufacturers can change a product's composition, and he pointed out that Monsanto itself had phased glyphosate out of its residential Roundup products. He also declined to strike Shull's punitive damages claim and allowed an amended petition focused on design and negligence.

Shull died before the order issued, so the case's own path is uncertain. But the reasoning matters to Aretino because it supplies the feasible-alternative-design argument from Monsanto's own conduct: if glyphosate-free residential Roundup exists on store shelves today, a jury can be told that a different design was possible.

The practical answer

Claim type	Status after Durnell	Leading authority
Failure to warn (label should have carried cancer warning)	Expressly preempted	Monsanto Co. v. Durnell (2026)
Design defect (product unreasonably dangerous as designed)	Not decided by the Supreme Court; allowed to proceed in Missouri	Bates v. Dow Agrosciences (2005); Shull (Boone Cty., Aug. 31, 2026)
Negligent testing / negligent design	Not decided; allowed to proceed in Shull	Bates; Shull
Manufacturing defect	Not preempted under Bates	Bates
Fraud or concealment premised on label content	Contested; at risk if it depends on what the label should have said	Durnell reasoning
Punitive damages	Available on surviving claims under state law	Shull (motion to strike denied)

What are the two sides arguing in the Roundup design defect trial?

The plaintiffs argue that Monsanto never adequately tested Roundup and engineered regulatory approval; Monsanto argues that decades of EPA and international regulatory reviews show glyphosate is safe and that the plaintiffs cannot prove the product was too dangerous to sell.

The plaintiffs: a testing case, not a label case

Dovel's opening was built to stay on the right side of the preemption line. "Monsanto did not adequately test Roundup," he told jurors, according to Reuters. "To this day, they've never done all the testing they've needed to do." Courtroom View Network reported that his presentation put far more weight than earlier Roundup openings on the underlying design and testing of glyphosate, arguing that the chemistry of the compound should have raised red flags that Monsanto chose not to investigate.

Dovel also went straight at the EPA, which is the strongest piece of Monsanto's defense. He told the jury the agency's conclusion that glyphosate is safe and needs no cancer warning rests on incomplete and outdated science, noted that EPA is in the middle of a new glyphosate review, and argued, in CVN's account, that "EPA approval of Roundup doesn't mean that it is safe." Reuters reported that he also accused Monsanto of minimizing decades of troubling test results, ghostwriting scientific papers, and engineering a dubious EPA approval, themes drawn from the internal company documents that have featured in Roundup trials since 2018.

The legal logic is deliberate. A failure-to-warn case says: the product was what it was, and users should have been told. A design and testing case says: a reasonable manufacturer would have studied the formulation, found the risk, and sold something else. Missouri's strict liability design defect standard asks whether the product, as designed, was unreasonably dangerous when put to a reasonably anticipated use, and negligence asks whether the manufacturer exercised ordinary care. Neither question turns on the label, which is what lets the plaintiffs argue Durnell does not apply.

Monsanto: the regulators already answered the question

Boehm told the jury the plaintiffs cannot show glyphosate-based herbicides are too dangerous to sell, because that claim contradicts decades of safety reviews by EPA and regulators around the world. CVN reported that he urged jurors to accept that EPA's findings are corroborated by other regulatory bodies and argued those findings alone undercut the design defect theory. Bayer has consistently said that decades of studies show glyphosate is safe and does not cause cancer.

The defense also gets a structural benefit from Durnell. In past trials, plaintiffs could argue that Monsanto should simply have added a warning, a low-cost fix that made jurors' decisions easy. A design case asks the jury to conclude that the product should not have been sold in its existing form at all, and Monsanto will press that a widely used agricultural herbicide approved by regulators on multiple continents cannot be "unreasonably dangerous" as a matter of design. Expect the defense to emphasize General Causation, arguing the epidemiology does not establish that glyphosate causes non-Hodgkin lymphoma, and Specific Causation for each plaintiff, which in a three-plaintiff trial means three separate exposure and medical histories.

How big have Roundup verdicts been?

The verdict history explains why both sides treat a single St. Louis County trial as a market signal. Large awards have been repeatedly cut on post-trial motions or appeal, but several survived in substantial amounts, and Missouri has produced some of the biggest.

Case	Court	Year	Jury award	What happened next
Johnson v. Monsanto	San Francisco Superior Court	2018	$289 million	Reduced on post-trial motion and appeal
Hardeman v. Monsanto	N.D. Cal. (MDL 2741 bellwether)	2019	$80 million	Reduced; Ninth Circuit affirmed liability
Pilliod v. Monsanto	Alameda County Superior Court	2019	About $2 billion	Reduced to about $87 million
Durnell v. Monsanto	City of St. Louis	2023	$1.25 million (warning claim only)	Reversed by U.S. Supreme Court, June 25, 2026
Anderson (four plaintiffs)	Cole County, Missouri	2023	$1.56 billion	Cut to $611 million; affirmed by Mo. Ct. App. W.D. May 27, 2025; Missouri Supreme Court declined review
McKivison v. Monsanto	Philadelphia Court of Common Pleas	2024	$2.25 billion	Reduced on post-trial motions
Aretino v. Monsanto	St. Louis County	2026	Pending	Openings Sept. 29, 2026

Two features of the history matter for Aretino. Many of the largest past verdicts rested in whole or part on warning theories that are now preempted, so they are imperfect predictors of what a design-only jury will do. And Monsanto has also won a series of Roundup trials, which means a defense verdict in St. Louis County would not be unprecedented, but would be the first one delivered under the new legal rules.

How does the trial affect the $7.25 billion Roundup settlement?

The Aretino trial does not directly affect the settlement, because the plaintiffs opted out, but its outcome will shape how attractive the settlement looks to every other claimant and how much leverage objectors and opt-outs have. A plaintiffs' verdict would show that opt-out claims still carry real value after Durnell; a defense verdict would reinforce Bayer's argument that the class deal is the best remaining option.

Where the settlement stands

The King v. Monsanto class settlement, announced in February 2026, would have Bayer make declining, capped annual payments for up to 21 years, totaling as much as $7.25 billion, to resolve current and future non-Hodgkin lymphoma claims from people exposed to Roundup. Individual awards are expected to range from roughly $10,000 to $165,000 depending on exposure, age at diagnosis and disease severity. Judge Boyer granted preliminary approval on March 4, 2026, and the opt-out deadline ran June 4.

Judge Boyer held the final fairness hearing on September 14, 2026, and reserved decision. More than 100 class members and roughly a dozen health plans filed objections, attacking notice, the opt-out mechanics, inconsistent treatment of claimants, and class counsel's $675 million fee request. As of October 1, 2026, no final approval order had issued. Our earlier report on the fairness hearing covers the objections in detail.

Why the opt-out math changed

Durnell reshaped the settlement's economics. Before June, an opt-out could expect to try a failure-to-warn case with a track record of large Missouri verdicts. After June, some claimants who had opted out sought to revoke their opt-outs and rejoin the class, and the hearing was delayed to give the claims administrator time to process those revocations. The Aretino plaintiffs did not take that path. Their trial is, in practical terms, the market test of the decision not to.

The connection to the class settlement runs in both directions:

• A large plaintiffs' verdict would strengthen objectors' argument that the settlement's $10,000-to-$165,000 grid undervalues claims, would give remaining opt-outs negotiating leverage for individual deals, and would make the futures release harder to defend if Judge Boyer has not yet ruled.
• A defense verdict would support Bayer's position that design claims are weak even before preemption is litigated on appeal, would make the class matrix look comparatively generous, and would likely depress the value of every non-participating inventory.
• A verdict for the plaintiffs that is later reversed on preemption would be the worst outcome for opt-outs: years of appellate delay, then nothing, with the settlement window long closed.

What happens to the Roundup MDL after Durnell?

The federal Roundup cases remain consolidated in MDL 2741, In re: Roundup Products Liability Litigation, before Judge Vince Chhabria in the Northern District of California. According to a litigation tracker citing the Judicial Panel on Multidistrict Litigation (JPML)'s September 1, 2026 report, about 3,925 actions remain pending in the MDL. The same source reports that Bayer has asked Judge Chhabria to dismiss the remaining federal cases on the theory that Durnell eliminates the warning theory the MDL was built on and that the surviving claims are repackaged warning claims, and that the court has set a process for deciding the motion but has not ruled.

That makes Judge Chhabria's eventual ruling the federal counterpart to Aretino. Missouri's state trial courts have so far allowed design claims to go forward, as in Shull. If a federal MDL judge with a decade of Roundup experience reaches the opposite conclusion, the split between state and federal forums would sharpen, and the forum choices of plaintiffs' firms would follow. MDL plaintiffs whose claims are dismissed on preemption grounds would still be within the class definition of the King settlement unless they opted out, so the timing of the two rulings, Boyer's and Chhabria's, interacts directly.

Does the EPA's new glyphosate review matter to the trial?

Yes, and both sides are already using it. In September 2026, EPA and the Department of Health and Human Services announced a memorandum of understanding to strengthen EPA's ongoing glyphosate review, with work focused on the toxicology of glyphosate formulations and surfactants, occupational epidemiology, human exposure and biomonitoring, and dietary exposure. Reporting on the agreement anticipates completion of the updated human health assessment in late 2026 or early 2027. The review follows a 2022 federal appellate decision that vacated EPA's earlier interim conclusion that glyphosate is not likely to be carcinogenic, and EPA's subsequent withdrawal of that interim decision.

For the plaintiffs, a review still in progress supports the argument that the science behind EPA's existing conclusion is incomplete and that Monsanto's own testing never filled the gaps. For Monsanto, decades of consistent regulatory conclusions, in the United States and abroad, are the core of its defense. The focus of the new review on formulations and surfactants, rather than glyphosate alone, also lines up with a design defect theory that targets the finished Roundup product.

Timeline: Roundup litigation from Durnell to Aretino

Date	Event
October 2023	City of St. Louis jury awards John Durnell $1.25 million on a failure-to-warn claim
November 2023	Cole County jury awards four Anderson plaintiffs $1.56 billion (later cut to $611 million)
February 2025	Missouri Court of Appeals, Eastern District, affirms Durnell
January 16, 2026	U.S. Supreme Court grants certiorari in Monsanto Co. v. Durnell
February 17, 2026	Bayer announces the $7.25 billion King v. Monsanto class settlement
March 4, 2026	Judge Timothy Boyer grants preliminary approval
June 4, 2026	Opt-out deadline
June 25, 2026	Supreme Court decides Durnell, 7-2, preempting failure-to-warn claims
August 31, 2026	Boone County Judge Jeff Harris denies Monsanto summary judgment in Shull, allowing design and negligence claims
September 14, 2026	Final fairness hearing on the class settlement; decision reserved
September 2026	EPA and HHS announce memorandum of understanding on glyphosate review
September 29, 2026	Opening statements in Aretino v. Monsanto, St. Louis County
Late Oct.–early Nov. 2026 (est.)	Expected close of the four-to-five-week trial

What it means for plaintiffs' firms, funders and defendants

For personal injury and mass tort firms

The Aretino trial is the first data point on how to try a Roundup case without a warning theory, and firms holding opt-out inventories should study the trial record, including the jury instructions on design defect and any rulings excluding label-based evidence. The line between permitted testing and design evidence and preempted warning evidence will be drawn objection by objection, and those evidentiary rulings may matter more to future trials than the verdict itself. Firms should also reassess intake: new claims are being filed, but a client's recovery now depends on surviving a preemption challenge that did not exist a year ago, along with ordinary Statute of Limitations and Discovery Rule questions tied to the date of diagnosis.

For litigation funders

For funders with exposure to Roundup inventories through Third-Party Litigation Funding arrangements, Durnell converted a portfolio priced on Missouri warning verdicts into a portfolio priced on an untested design theory plus appellate preemption risk. Aretino is the first price signal on that new risk. A plaintiffs' verdict would support continued investment in opt-out claims; a defense verdict, or a later appellate reversal on preemption, would push inventories toward the class settlement and reduce the value of positions taken before June. Contingency Fee economics move the same way: a case that may take three more years to clear appellate review is worth less to the firm carrying it.

For defendants and other FIFRA registrants

The case matters well beyond glyphosate. Every pesticide manufacturer facing tort claims, including in the paraquat and chlorpyrifos litigations, now knows that a FIFRA preemption win on warnings will be met with a pivot to design and testing theories. If Missouri courts and juries accept that pivot, Durnell will have narrowed rather than closed pesticide product liability. Defendants should expect plaintiffs to cite a manufacturer's own reformulations, as Judge Harris did in Shull, as proof that a feasible alternative design existed, and should weigh that exposure when deciding whether and how to change product formulations.

For class settlement practice

The relationship between the King settlement and the Aretino trial is a live example of how individual opt-out trials discipline a Global Settlement. Objectors and courts evaluating fairness look at what opt-outs actually recover. Whether Judge Boyer rules before or after the Aretino verdict, the trial result will become part of the record anyone challenging or defending the settlement on appeal will cite.

Frequently asked questions

What is the first Roundup trial after Monsanto v. Durnell?

It is Aretino, et al. v. Monsanto Co., No. 20SL-CC03676, in the Circuit Court of St. Louis County, Missouri, before Judge Brian May. Opening statements were held September 29, 2026, and the three plaintiffs are pursuing design defect claims only.

Are Roundup design defect claims preempted after Durnell?

The Supreme Court did not decide that question. Durnell preempted failure-to-warn claims, while Bates v. Dow Agrosciences (2005) said design defect and testing rules are not labeling requirements; a Missouri judge in Shull allowed design claims to proceed on August 31, 2026. Monsanto argues they are still preempted and will raise the issue on appeal.

How does the Aretino trial affect the $7.25 billion Roundup settlement?

The Aretino plaintiffs opted out, so the trial does not change the settlement's terms. Its result will affect how valuable opt-out claims look, how much leverage objectors have, and how the settlement's fairness is argued if Judge Boyer's eventual approval decision is appealed.

What happens to the Roundup MDL after Durnell?

The federal cases remain in MDL 2741 before Judge Vince Chhabria in the Northern District of California, with roughly 3,925 actions pending as of September 1, 2026, according to a tracker citing JPML data. Bayer has asked the court to dismiss the remaining federal cases as preempted; no ruling has been reported.

Can you still file a Roundup lawsuit after the Supreme Court ruling?

Yes. Durnell bars claims that the Roundup label needed a cancer warning, but it did not bar design defect, negligent testing, or manufacturing defect claims, and new cases continue to be filed. Whether a claim is timely depends on state statutes of limitations, usually measured from diagnosis, and anyone within the King class definition who did not opt out may be bound by that settlement if it receives final approval.

When will the Roundup trial in St. Louis County end?

Courtroom View Network has estimated the trial will take four to five weeks from the start of proceedings in late September 2026, which would put closing arguments and a verdict in late October or early November 2026. Any plaintiffs' verdict is widely expected to be appealed on preemption grounds.