SAN FRANCISCO (CN) – Attorneys for a school groundskeeper suing Monsanto over his terminal lymphoma suggested to a California jury Friday that the agrichemical company submitted fraudulent cancer data to U.S. regulators so it could sell its Roundup weed killer, against court orders barring testimony on the topic.

The study to which Baum Headland Aristei Goldman attorney Brent Wisner had referred was done in the mid-1970s by Industrial Bio-Test (IBT) Laboratories. Monsanto hired the now-defunct lab to conduct toxicology studies on Roundup’s active ingredient glyphosate, which are required for the approval of herbicides by the U.S. Environmental Protection Agency.

Roundup was initially approved for sale in 1974 based in part on the IBT data. But the data was later found to contain discrepancies invalidating IBT’s conclusions that glyphosate was safe.

A subsequent review by the EPA found that IBT routinely falsified data, and three of its executives were convicted of fraud, according to plaintiff DeWayne Johnson’s complaint.

It is “hard to believe the scientific integrity of the studies when they said they took specimens of the uterus from male rabbits,” an EPA reviewer said of IBT at the time, according to the complaint.

Monsanto wasn’t responsible for the faulty study, and testimony regarding it had been excluded before trial so as not to bias the jury.

But Wisner alluded to the study while questioning an expert witness Friday about a set of animal cancer studies done in the early 1980s, leaving the impression that Monsanto knowingly submitted fraudulent data to get around the EPA’s licensing requirements.

“We just established that Roundup was approved in the 1970s, yet this mouse study was done in 1983 and this rat study was done in 1981,” Wisner said of the studies, which were part of Roundup’s 1974 licensing documentation. “Is it fair to say that between the original registration and [the early 1980s], there were no valid mouse or rat studies” of glyphosate’s carcinogenicity?

Hollingsworth LLP attorney Kirby Griffis, who represents Monsanto, objected to the question, which was sustained.

Later, however, another question by Wisner led the expert, Charles Benbrook, to testify that Monsanto “didn’t have any valid studies” in the 1970s despite Roundup’s 1974 approval date.

George Lombardi, an attorney with Winston & Strawn also representing Monsanto, expressed frustration with Wisner during the jury’s lunch recess. He asked San Francisco County Superior Court Judge Suzanne Ramos Bolanos to strike the testimony and bar Wisner from mentioning the IBT studies again.

“That was obviously in direct violation of the order of this court,” Lombardi said. “This time, it was a question put by counsel, it wasn’t just a witness blurting it out.”

The comment was in reference to an expert witness about whom Lombardi complained Thursday over purposely testifying about topics on which he had been instructed not to testify.

Wisner told Bolanos he was “so surprised” by Monsanto’s objections, because he and Lombardi had struck a deal allowing him to tell the jury that Roundup was approved in the 1970s but that the EPA had asked Monsanto to repeat the 1983 study, as long as he didn’t mention IBT by name.

But Lombardi said Wisner had used the phrase “invalid studies,” which “is the same as saying ‘fraudulently derived,'” therefore nullifying the deal.

Bolanos appeared to side with Lombardi, and said she would consider striking the testimony.

Although U.S. and European regulators have concluded glyphosate is safe, the WHO’s International Agency for Research on Cancer classified it in 2015 as a probable human carcinogen, triggering a slew of lawsuits against Monsanto in the U.S., including Johnson’s.

Johnson, 46, sued Monsanto in 2016 after being diagnosed with a cutaneous form of non-Hodgkin lymphoma that caused cancerous lesions to form over most of his body. He says he developed symptoms after he was twice drenched in Roundup while spraying schoolyards for his job with the school district in Benicia, a suburb of San Francisco.

He also claims Monsanto has known for decades that Roundup is carcinogenic but didn’t disclose it for fear of disrupting its multi-billion dollar global business.

Part of its strategy, he claims, is suppressing scientific evidence that Roundup is carcinogenic, including the 1983 study.

The study found a statistically significant number of benign and malignant kidney tumors in a group of male mice dosed with high amounts of glyphosate, prompting the EPA to classify the chemical in 1985 as a possible human carcinogen.

But a reevaluation by Monsanto revealed an additional benign tumor in the control group, and the company concluded that the reported cancer was no longer statistically significant.

The EPA subsequently withdrew its carcinogenicity finding – Johnson claims it did so due to pressure by Monsanto – but recommended that the company repeat the study.

Monsanto refused, according to Benbrook, an expert in pesticide regulation and pesticide risk assessment.

“This may be the most debated tumor in the history of carcinogenicity,” Benbrook said, because researchers continue to puzzle over it today.

On cross-examination, Griffis also said the additional tumor drove the results “away from significance.”

But Wisner countered that the historical control group data showed the reported tumors were rare, indicating they were triggered by glyphosate.

According to the historical control group data, three out of 900 mice developed the tumors in question.

Glyphosate is the most widely used agrichemical in history. Monsanto introduced it in 1974, and its use exploded in 1996 after the company began selling “Roundup-ready” seeds engineered to resist the herbicide. More than 2.6 billion pounds of the chemical were spread on U.S. farmlands and yards between 1992 and 2012, according to the U.S. Geological Survey.

Monsanto earns $1.9 billion a year from Roundup and $10.2 billion from “seeds and genomics,” most of that category being Roundup-ready seeds.

In June, German pharmaceutical giant Bayer completed its $63 billion purchase of Monsanto after approval by U.S. and European regulators. Bayer told Reuters the same month that it plans to retire the Monsanto name.

Testimony continues Monday.