Judge leaning toward excluding some Monsanto expert testimony

The San Francisco federal judge overseeing litigation on allegations Monsanto Co.'s glyphosate-based weed killer causes cancer indicated he is inclined to exclude portions of the defense's expert witness testimony.

U.S. District Judge Vince Chhabria prohibited the agrochemical company's experts from analyzing epidemiological literature to support an opinion that Roundup is not a risk factor for developing Non-Hodgkin lymphoma while keeping the door open to potentially allow for testimony on other issues related to general causation, according to a tentative ruling.

"Monsanto disclosed reports from specific causation experts that effectively included opinions on general causation -- i.e., that Roundup is simply not a risk factor for NHL," Chhabria wrote on Monday. "It appears that these opinions should, in large part, be excluded."

Defense attorneys will have the chance to dispute the judge's tentative order in the last evidentiary hearing Wednesday.

It could "presumably" be appropriate for the experts to opine on general causation to "attack the decision by the plaintiffs' experts to exclude other risk factors," the judge wrote.

Monsanto, now owned by Bayer AG, must prove it will be prejudiced by the ruling despite being allowed to "present general causation testimony from numerous other witnesses (and how it would not be a waste of the jury's time to have more than those witnesses testifying on the topic of general causation)," Chhabria added.

Plaintiff Edwin Hardeman alleged Roundup was a substantial factor in his development of Non-Hodgkin lymphoma. His case will be the first of the three bellwether trials.

The defense argues Hardeman's cancer could have been caused by his hepatitis C or obesity. In re Roundup Products Liability Litigation, 16-MD02741 (N.D. Cal., filed Oct. 4, 2016).

On Wednesday, Chhabria will also consider Monsanto's challenges to the plaintiff's expert witnesses who testified on issues related to general causation. He and defense attorney Tamarra M. Johnson of Wilkinson, Walsh & Eskovitz pressed plaintiff's expert pathologist Dennis Weisenburger at an evidentiary hearing on Monday concerning other possible causes of Hardeman's cancer.

In a long series of questions seemingly aimed at probing the pathologist's potential biases to reach his conclusion Roundup is a substantial contributing factor to developing Non-Hodgkin lymphoma, Chhabria asked Weisenburger if his methodology allowed for inconclusive results as to what caused Hardeman's cancer.

"Yes, it [does]," he said. "It goes back to the initial interpretation of all general causation data. If you believe that Roundup can cause NHL, and you believe there's strong evidence ... then you'd use that in your interpretation of specific causation."

The first phase of the bifurcated trial will only consider issues of causation. If the jury finds Monsanto liable, it will then consider allegations of misconduct and whether punitive damages are warranted.

Monsanto attorneys sought to exclude the presentation of mention of other litigation against the company, evidence regarding the company's public relations activities and comparisons to the tobacco industry, among other matters.

The plaintiff's attorneys wanted to prohibit evidence concerning information about an attorney advertising for plaintiffs in the Roundup litigation, Hardeman's "unrelated medical history," according to his attorney Aimee H. Wagstaff of Andrus Wagstaff PC, and evidence about foreign regulatory decisions.

Jury selection begins Friday.