[2] The case drew worldwide attention and is widely misunderstood to concern what happens when farmers' fields are accidentally contaminated with patented seed.

[5] He had used Roundup herbicide to clear weeds around power poles and in ditches adjacent to a public road running beside one of his fields, and noticed that some of the canola which had been sprayed had survived.

Monsanto then sued Schmeiser for patent infringement, filing its case in Canadian federal court on August 6, 1998.

[5] Negotiations to settle the matter collapsed on August 10, 1999, leading Schmeiser to file a countersuit against Monsanto for $10 million for libel, trespass, and contaminating his fields.

"[5] Beginning with the lead-up to the initial Federal Court trial, the case drew widespread public attention and media coverage.

[9][10][11] Environmental groups and anti-genetic engineering activists championed Schmeiser's cause and he spoke on the case around the world.

[13][14][15] Monsanto v. Schmeiser was portrayed as being part of the process of legally defining the bounds of new biotechnologies, including genetic engineering and ownership of higher lifeforms.

[9] The Canadian Supreme Court eventually took pains to point out that the Monsanto v Schmeiser case focused on genes in seeds, and not on higher life forms; it was "the first in which the top court of any country has ruled on patent issues involving plants and seed genes.

Both courts found that a key element in Mr. Schmeiser's patent infringement in his 1998 crop was that he knew or ought to have known the nature of the glyphosate-resistant seed he saved and planted.

Nonetheless, at trial, Monsanto was able to present evidence sufficient to persuade the Court that Roundup Ready canola had probably not appeared in Schmeiser's 1997 field by such accidental means (paragraph 118[5]).

[5]: Para 115  On this point, the Federal Court of Appeal noted that accidental genetic contamination of a crop beyond a farmer's control should be an exception to the rule that intent is not an issue in patent disputes.

[18] The Federal Court of Appeal in particular stressed the importance of the finding that Schmeiser had knowingly used the seed, in their decision to find Schmeiser in infringement of the patent, and noted that in a case of accidental contamination or a case where the farmer knew of the presence of the gene but took no action to increase its prevalence in his crop, a different ruling could be possible (see paragraphs 55-58 of the appeal ruling[18]).

The Court considered the question of whether knowingly (or, where one ought to have known) planting and cultivating genetically modified canola constitutes "use" of Monsanto's patented invention of genetically modified canola cells, even if the crop is not treated with Roundup and the presence of the gene affords no advantage to the farmer.

In the ruling, the court made it clear that patent infringement was the sole consideration, and concerns related to genetic engineering in agriculture were not within the scope of the case: Arbour J., writing for Iacobucci, Bastarache, and LeBel JJ., dissented in part.

This majority view, based on the precedent of mechanical devices, was central to the Supreme Court's decision, and put the onus on the Canadian Parliament to make distinctions between machines and lifeforms as it saw fit.

In 2005, a "documentary theatre" production dramatizing the court battle, entitled Seeds, by Annabel Soutar, was staged in Montreal, Quebec.

The case is widely cited or referenced by the anti-GM community in the context of a fear of a company claiming ownership of a farmer’s crop based on the inadvertent presence of GM pollen grain or seed.

[22][23] "The court record shows, however, that it was not just a few seeds from a passing truck, but that Mr Schmeiser was growing a crop of 95–98% pure Roundup Ready plants, a commercial level of purity far higher than one would expect from inadvertent or accidental presence.

The judge could not account for how a few wayward seeds or pollen grains could come to dominate hundreds of acres without Mr Schmeiser’s active participation, saying ‘.

.none of the suggested sources could reasonably explain the concentration or extent of Roundup Ready canola of a commercial quality evident from the results of tests on Schmeiser’s crop’" - in other words, even if the original presence of Monsanto seed on his land in 1997 was inadvertent, the crop in 1998 was entirely purposeful.