SAN FRANCISCO (Reuters) - A trial in which a California man alleged his use of Bayer AG’s glyphosate-based Roundup weed killer caused his cancer went to a federal U.S. jury after lawyers for both sides delivered their closing arguments on Tuesday.

FILE PHOTO: Monsanto's Roundup weedkiller atomizers are displayed for sale at a garden shop at Bonneuil-Sur-Marne near Paris, France, June 16, 2015. REUTERS/Charles Platiau/File Photo

The closely-watched case brought by plaintiff Edward Hardeman is only the second of some 11,200 Roundup lawsuits to go to trial in the United States. Another California man was awarded $289 million in August after a state court jury in August found Roundup caused his cancer, sending Bayer shares plunging.

Hardeman’s case has proceeded differently from the earlier trial, with an initial phase exclusively focused on scientific facts while omitting evidence of alleged corporate misconduct by company representatives.

Following the first phase, the six jurors in San Francisco federal court were asked by U.S. District Court Judge Vince Chhabria to decide whether Roundup was a “substantial factor” in causing Hardeman’s cancer.

If the jury finds Roundup to have caused Hardeman’s cancer, the trial will proceed into a second stage, where his lawyers can present evidence allegedly showing the company’s efforts to influence scientists, regulators and the public about the safety of its products.

Hardeman’s lawyer, Aimee Wagstaff, during her closing arguments on Tuesday said Hardeman had “extreme” exposure to Roundup, spraying the chemical more than 300 times over 26 years.

“The dose makes the poison. The more you use, the higher the risk,” Wagstaff said. She urged jurors to consider all studies, including of rodents and cells, which she said showed an elevated cancer risk.

Bayer, which acquired Monsanto for $63 billion, denies allegations that Roundup, or glyphosate, cause cancer. It says decades of studies and regulatory evaluations, primarily of real-world human exposure data, have shown the weed killer to be safe for human use regardless of exposure levels.

Wagstaff criticized the epidemiological studies as flawed.

Brian Stekloff, a lawyer for Bayer, in his closing statement said the cause of Hardeman’s cancer, and non-Hodgkin’s lymphoma generally, was not known.

“No one can tell you the cause,” Stekloff said, adding that Hardeman had some risk factors, such as old age and a history of hepatitis.

Chhabria decided in January to split Hardeman’s case into two phases. He called evidence of alleged corporate misconduct “a distraction” from the scientific question of whether glyphosate causes cancer.

Hardeman’s trial is a test case for some 760 cases nationwide consolidated before Chhabria in federal court.

Evidence of corporate misconduct was seen as playing a key role in the earlier state court case. The verdict in that case was later reduced to $78 million and is on appeal.

Plaintiff lawyers called Chhabria’s decision to exclude similar evidence from the first phase of Hardeman’s case “unfair,” saying their scientific evidence was inextricably linked to Monsanto’s alleged attempts to manipulate, misrepresent and intimidate scientists.