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A lawyer representing a Northern California man who claims that exposure to Monsanto Co.’s Roundup weedkiller caused him to develop cancer urged a San Francisco jury to consider the amount and duration of his exposure.

Aimee Wagstaff of Andrus Wagstaff on Tuesday pointed to expert testimony that concluded that her client Edwin Hardeman sprayed about 6,000 gallons of Roundup on his property over a 26-year span. Monsanto’s experts, she argued, didn’t consider the amount her client sprayed or the duration of his exposure when they concluded that Roundup wasn’t a significant factor contributing to his cancer.

“The dose makes the poison,” Wagstaff repeated during closing arguments Tuesday in the first bellwether trial in the multidistrict Roundup litigation pending before U.S. District Judge Vince Chhabria of the Northern District of California.

Chhabria bifurcated the trial to frontload the question of whether or not Monsanto’s Roundup herbicide was a significant cause of plaintiff Hardeman’s non-Hodgkins lymphoma. If the jury unanimously finds that a preponderance of the evidence shows that Roundup was a significant factor contributing to Hardeman’s cancer, the case will move onto a second phase to  consider what Monsanto knew, how the company conducted itself, and potential damages. A finding that Roundup was not a significant factor would be a victory for the defense and the end of the first bellwether trial, but not the MDL. If the six-member jury is unable to reach a unanimous verdict, the result would be a mistrial, and Hardeman’s case could be tried again.

Closing arguments Tuesday went significantly smoother for Wagstaff than the opening of trial did. Chhabria interrupted Wagstaff’s opening repeatedly and later sanctioned her $500 for what he called “obvious violations” of his pretrial orders during her opening presentation. The judge also ordered Wagstaff to hand over a list of every other attorney who worked on the opening within two weeks of the end of Hardeman’s trial for additional possible sanctions.

The stakes are significant for Monsanto’s parent company Bayer AG, which last year was hit with a $289 million verdict in San Francisco Superior Court in a Roundup case outside the MDL proceedings. The state court judge overseeing that case, however, slashed the award by more than $200 million.

Pretrial and away from the jury, Chhabria has expressed skepticism about the strength of plaintiffs’ scientific evidence. In July, he narrowly allowed plaintiffs’ cases in the MDL to move forward, but called evidence that glyphosate—the active ingredient in Roundup—causes non-Hodgkin’s lymphoma “shaky” but “admissible.” He wrote that plaintiffs had a “daunting challenge” to prove causation.

Aside from the trial structure, Hardeman’s case has some significant differences from the state court trial that yielded the blockbuster verdict. The plaintiff in the state case, Dewayne “Lee” Johnson, was diagnosed with non-Hodgkin’s lymphoma, or NHL, after spraying a Monsanto herbicide as part of his job as a school groundskeeper. Johnson’s case was fast-tracked for trial because of his dire prognosis. Hardeman, by contrast, is in remission from cancer and developed NHL after using Roundup on his own property to clear poison oak and weeds from hiking trails and his driveway. He also had Hepatitis for decades, something that Monsanto’s lawyers argued was a significant risk factor for him contracting NHL.

But in her closings, Wagstaff pointed out that Hardeman’s Hepatitis never resurfaced throughout his six rounds of chemotherapy to treat his cancer. “Not one time did the Hep C ever show up,” she said. “So where are the facts of this Hep C swimming around at undetectable level? They’re just not there.”

Brian Stekloff, a lawyer at Wilkinson Walsh + Eskovitz who is representing Monsanto in the Hardeman trial, pointed out that the plaintiff’s treating physicians had never asked about his Roundup use or tied it to his diagnosis.

“Roundup did not factor into their treatment, whatsoever,” he said. He also said that the Hardeman’s lawyers were falsely trying to make the case an issue of “Roundup versus Hepatitis C.” In reality, he argued, that Hardeman’s causation expert had testified that Roundup was the primary factor driving his cancer.

“The case they have presented to you is that it is Roundup and Roundup only,” he said “No one has come into this courtroom and said it could have been both.”

Stekloff further argued that the largest human study to look at whether use of the active ingredient in Roundup caused cancer—a long-term study of agricultural workers called the Agricultural Health Study—found that levels of NHL among those exposed were similar to those in the general population—about 1 percent in both. Stekloff said that “if what they’re saying is true if Roundup is this huge problem that is causing cancer everywhere” you would expect to see a spike in NHL cases in the wake of the exponential increase of Roundup use since the 1990s.

The number of cases, he said, has remained steady.