"A unanimous jury in San Francisco has told Monsanto: "Enough".
The groundsman's lawyers said he was diagnosed with non-Hodgkin's lymphoma in 2014, having used Roundup and a similar Monsanto product, Ranger Pro, in large quantities while working for a school authority.
"The jury found Monsanto acted with malice and oppression because they knew what they were doing was wrong and doing it with reckless disregard for human life", one of Johnson's attorneys, Robert F. Kennedy Jr., said.
"Monsanto made Roundup the oxycontin of pesticides and now the addiction and damage they caused have come home to roost", said Ken Cook, President of the Environmental Working Group, a US environmental organization that researches toxic chemicals and advocates for corporate accountability. "I hope it gets the attention that it needs".
Dewayne Johnson was emotional after hearing the verdict. But the World Health Organization's cancer arm in 2015 classified glyphosate as "probably carcinogenic to humans".
A spokesman for Monsanto, the company behind Roundup, said the agribusiness will appeal the ruling.
Johnson said he hoped his verdict would bolster the other cases.
Wisner called the ruling the "tip of the spear" of litigation likely to come.
House of Fraser's website is down as administration rumours swirl
It said it had put questions to House of Fraser earlier this week in relation to its future but has not yet received a response. HoF chief executive Alex Williamson said: "We are hopeful that the current negotiations will shortly be concluded".
Monsanto, a subsidiary of German firm Bayer AG, has denied glyphosate is linked to cancer, saying hundreds of studies have found the product to be safe.
Robert F. Kennedy Jnr - an environmental lawyer, son of the late United States senator and a member of Johnson's legal team - hugged Johnson after the verdict. "This won't cure DeWayne Lee Johnson's cancer, but it will send a strong message to a renegade company".
"We are sympathetic to Mr Johnson and his family", Mr Partridge said. "The verdict today does not change the science".
Johnson's team expressed confidence in the verdict, saying the judge in the case kept out a mountain of more evidence backing their position. Monsanto is being accused of hiding the dangers of its popular Roundup products.
"You not only see many people injured, you see the corruption of public officials, the capture of agencies that are supposed to protect us from pollution and the falsification of science", Kennedy said. "In many ways, American democracy and our justice system was on trial in this case". "It's just a matter of time", Wisner told the jury in his opening statement last month. - The jury ordered agrochemical giant Monsanto to pay almost $290 million for failing to warn a dying groundskeeper that its weed killer Roundup might cause cancer.
Four years later Johnson - now near death, according to his doctors - has been awarded a staggering sum of $289 million dollars in damages in a case against agricultural giant Monsanto.
Glyphosate is the world's most common weedkiller. It was expedited because court filings indicated that Johnson was dying.
Monsanto was one of the companies that produced the defoliant "Agent Orange" - which has been linked to cancer and other diseases - for use by U.S. forces in Vietnam. The company has employed a range of tactics - some drawn from the same playbook used by the tobacco industry in defending the safety of cigarettes - to suppress and manipulate scientific literature, harass journalists and scientists who did not parrot the company's propaganda, and arm-twist and collude with regulators. Monsanto launched Roundup in 1976 and soon thereafter began genetically modifying plants, making some resistant to Roundup.