A single farmer from the Canadian Prairies is preparing to take on a mighty biotech corporation in his country's Supreme Court.
Percy Schmeiser, a sprightly 72-year-old from Bruno, Saskatchewan, has become a hero to the anti-GM movement worldwide for resisting Monsanto's attempts to enforce its patent rights over the seeds it promotes.
Schmeiser has mortgaged much of his land to pay legal fees
The outcome of the case could have major implications not just for genetically modified crops, but for the patenting of genetic techniques in many other areas.
Mr Schmeiser's battle with Monsanto dates back to 1998, when it accused him of planting the company's genetically modified canola (oilseed rape) on his land without permission, and demanded that he pay it the same fee required of those growing GM crops under contract.
He refused, saying that he had simply followed his usual practice of collecting seeds from his own crop to plant for the following year, and that it must have become contaminated from GM canola grown nearby.
Mr Schmeiser told BBC News Online: "I was very concerned, because we realised that there was contamination of the pure seed we had been developing for half a century.
"We said to Monsanto when we received the law suit, 'if you have any GMOs in our pure seed, you should be liable and there should be a law suit against you people'."
Monsanto claimed the level of herbicide resistance in the crop was such that it could not have happened accidentally, but the company did not prove this in court - it did not need to.
Because the judge in the original case ruled that it did not matter how the seed came to be in Mr Schmeiser's field, he was deemed to have infringed the company's patent rights simply by growing and harvesting it without permission.
It made no difference that he did not spray the crop with Monsanto's Roundup weedkiller and therefore did not benefit from the altered genetic structure of the plant.
Stuart Wells, of the Canadian National Farmers' Union, says the ruling has deterred some farmers from complaining when they find unwanted GM "volunteers" or "weeds" in their fields.
"I suspect that there are a lot of farmers who are not even reporting contamination to Monsanto because they don't want a company with the control they have to know that they have been polluted.
Canola, like any crop, will spread to other fields
"It's sort of a Catch-22 situation, if the farmer has no control whatsoever, and might end up in the sort of trouble that Monsanto is heaping on Percy Schmeiser."
Monsanto itself says it will never pursue farmers when GM seeds accidentally appear on their land, but says it will protect its patent rights when its technology is deliberately misappropriated.
Might and mouse
Mr Schmeiser's lawyers will argue in the Supreme Court that companies have no right to patent an entire plant, and they have been heartened by a recent ruling from the same court involving the "Harvard Mouse".
In that case, Harvard University claimed a patent on a mouse genetically altered to make it more susceptible to cancer for use in medical research, but the court ruled that a "higher life form" could not be classed as an invention.
Percy Schmeiser has had to mortgage much of his land to pay his legal fees, and admits that the five-year battle has caused enormous stress, but he says he does not regret it.
"We felt that what we were fighting for was not only for ourselves, but for farmers around the world, for their right to use their own seed. That's why we stood up to them."