A California groundskeeper dying of cancer said Monday he would ‘never’ have used Monsanto weed killer Roundup, had he known it could lead to his terminal illness.
The trial pitting 46-year-old Dewayne Johnson against the agrochemical colossus is expected to last into August, with the potential for a major impact on the company recently acquired by Germany-based Bayer.
The case is the first to reach trial alleging a cancer link from Roundup, one of the world’s most widely used herbicides.
The legal clash involves dueling studies, along with allegations Monsanto connived behind the scenes to thwart potentially damning research.
Diagnosed in 2014 with non-Hodgkin’s lymphoma, a cancer that affects white blood cells, Johnson told jurors he sprayed Roundup and especially its more powerful professional grade Ranger Pro product for two years at a school in Benicia, California.
One of his lawyers, David Dickens, held a Ranger Pro dispenser in his hand as he asked Johnson whether he would have used the product if he had seen a cancer warning on the label.
‘I would never have  sprayed RP in schools or anywhere else,’ replied Johnson, whose job as groundskeeper including ridding the area of pests and weeds with the help of up to 150 gallons (560 liters) of diluted solution per day.
Twice, a lot of product got on his skin and clothes because of a vaporizer malfunction, and Johnson experienced an ‘uncontrollable situation on my skin.’
He called the Monsanto hotline, but received no follow-up calls from representatives despite promises they would do so.
Johnson, who sat in court with his lawyer and wife, watched as his dermatologist Ope Ofodile testified in California Superior Court.
Ofodile testified that Johnson consulted her when he noticed a rash on his body starting in 2014.
‘He was frightened by the state of his skin,’ the physician told the trial.
After seeing the rash, Ofodile said she sent a letter to the school district board saying ‘that he shouldn’t be exposed to any airborne chemicals that could worsen his condition.’
Asked whether she was referring to Ranger Pro, she said, ‘Yes.’
But the physician said she did not investigate what caused the rash, and that she was focusing on treating the patient rather than establishing a link to Roundup.
Johnson had little warning about the risks of Roundup, his lawyer said in opening statements earlier this month.
‘He was told you could drink it, it was completely non-toxic,’ lawyer Brent Wisner claimed in his opening remarks.
The lawyer said Johnson, who is between rounds of chemotherapy, ‘is actually on borrowed time – he is not supposed to be alive today.’
A key to Johnson’s case will be convincing jurors that Monsanto’s pesticide – whose main ingredient is glyphosate – is responsible for the illness. 
Wisner contended that glyphosate combined with an ingredient intended to help it spread over leaves in a cancer-causing ‘synergy.’
Potential impact of case
Whether glyphosate causes cancer has been the source of long debate among government regulators, health experts and lawyers.
If Monsanto loses, the case could open the door to hundreds of additional lawsuits against the company.
Monsanto has denied any link with the disease and says studies have concluded the product is safe.
‘Mr Johnson’s cancer is a terrible disease. We all do and we all should have great sympathy for what he is going through,’ Monsanto defense attorney George Lombardi said during his opening remarks.
But the lawyer maintained that ‘the scientific evidence is overwhelming that glyphosate-based products do not cause cancer, and did not cause Mr Johnson’s cancer.’
Monsanto’s flagship herbicide Roundup was launched in 1976.
Roundup has been approved by the US Environmental Protection Agency, according to Lombardi.
In 2015, the International Agency for Research on Cancer – a World Health Organization body – classified glyphosate as ‘probably carcinogenic,’ and as a result, the state of California listed it as carcinogenic.
Founded in 1901 in St Louis, Missouri, Monsanto began producing agrochemicals in the 1940s. It was acquired by Bayer for more than $62 billion in June.