SAN FRANCISCO — A Northern California judge on Monday upheld a jury’s verdict that found Monsanto’s weed killer caused a groundskeeper’s cancer, but she slashed the amount of money to be paid from $289 million to $78 million.

In denying Monsanto’s request for a new trial, San Francisco Superior Court Judge Suzanne Bolanos cut the jury’s August punitive damage award from $250 million to $39 million. The judge had earlier said she had strong doubts about the jury’s entire punitive damage award.

Bolanos gave DeWayne Johnson until Dec. 7 to accept the reduced amount or demand a new trial.

Johnson’s spokeswoman Diana McKinley said he and his lawyers are reviewing the decision and haven’t decided the next step. “Although we believe a reduction in punitive damages was unwarranted and we are weighing the options, we are pleased the court did not disturb the verdict,” she said.

Monsanto spokesman Daniel Childs said that the company was pleased with the reduced reward but still planned to appeal the verdict. Childs said there’s no scientific proof linking Roundup to cancer.

The jury awarded punitive damages after it found that the St. Louis-based agribusiness had purposely ignored warnings and evidence that its popular Roundup product causes cancer, including Johnson’s lymphoma.

In a tentative ruling on Oct. 11, Bolanos said it appeared the jurors overreached with their punitive damages award. She said then that she was considering wiping out the $250 million judgment after finding no compelling evidence presented at trial that Monsanto employees ignored evidence that the weed killer caused cancer.

The judge reversed course Monday and said she was compelled to honor the jurors’ conclusions after they listened to expert witnesses for both sides debate the merits of Johnson’s claim.

The judge said jurors are entitled to accept the conclusion of Johnson’s expert witness who said Roundup caused his cancer and reject the conclusions of Monsanto’s expert witnesses, who concluded there’s no proof the weed killer causes cancer.

“Thus, the jury could conclude that Monsanto acted with malice by consciously disregarding a probable safety risk,” Bolanos wrote in her ruling.

Some jurors were so upset by the prospect of having their verdict thrown out that they wrote to Bolanos, the San Francisco Chronicle reported.

“I urge you to respect and honor our verdict and the six weeks of our lives that we dedicated to this trial,” juror Gary Kitahata wrote. Juror Robert Howard said the jury paid “studious attention” to the evidence and any decision to overturn its verdict would shake his confidence in the judicial system.

Johnson’s lawsuit is among hundreds alleging Roundup caused cancer, but it was the first one to go to trial.

Johnson sprayed Roundup and a similar product, Ranger Pro, at his job as a pest control manager at a San Francisco Bay Area school district, according to his attorneys. He was diagnosed with non-Hodgkin’s lymphoma in 2014 at age 42.

Many government regulators have rejected a link between the weed killer’s active chemical — glyphosate — and cancer.