DUPONT WENT TO COURT this week, defending its use of C8, the chemical that spread from the company’s Parkersburg, West Virginia, plant into the drinking water of some 80,000 people in West Virginia and Ohio. A jury in Columbus, Ohio, is now hearing the case of Carla Bartlett, a 59-year-old woman who developed kidney cancer after drinking C8-contaminated water for more than a decade.

As The Intercept reported in a three-part series last month, Bartlett’s is the first of some 3,500 personal injury and 37 wrongful death claims stemming from the 2005 settlement of a class-action suit filed on behalf of people who lived near the plant. Another trial over the chemical, which for decades was used in the production of Teflon and many other products, is scheduled for November. Together, the “bellwether” cases, six in all, are expected to give attorneys on both sides a sense of whether the rest of the claims will proceed or settle — and for how much.

Bartlett’s attorneys, including Robert Bilott, who has been working on C8 since taking the case of a West Virginia farmer named Wilbur Tennant in 1999, argue that DuPont is guilty of negligence, battery, and infliction of emotional harm for exposing Bartlett to C8 in her drinking water.

DuPont’s attorneys, who summarized their case in opening arguments and will present their witnesses later in the trial, insist that the company bears no responsibility for the kidney tumor for which Bartlett was treated in 1997. “Nobody at DuPont expected that there would be any harm from the extremely low levels of C8 that were reached in the community,” said DuPont’s attorney Damond Mace in his opening argument.

The company’s defense hinges on the contention that company employees did not realize C8 was dangerous at the time Bartlett was exposed — despite hundreds of internal documents detailing DuPont’s knowledge that the chemical posed risks to both animals and humans. When evidence of its harm did emerge, said Mace, it was too late: “Nothing that happened after 1997 would have allowed DuPont to go back and do things any differently than had already been done.”

The particular threats posed by the chemical were detailed by the findings of a panel of scientists, who in 2012 determined that C8 exposure at the level measured in six water districts — at least .05 parts per billion — was “more likely than not” linked with six illnesses: preeclampsia; ulcerative colitis; high cholesterol; thyroid disease; testicular cancer; and Bartlett’s disease, kidney cancer.

“Kidney cancer occurs every day all across this great country of ours.”

The 2005 class-action settlement requires DuPont to accept C8’s links to these diseases, and that agreement forces the company’s attorneys to walk a legal tightrope over causality. While they must admit that C8 can cause kidney cancer, they deny that it caused Bartlett’s particular cancer. As Mace told the jury: “Kidney cancer occurs every day all across this great country of ours.” He then pointed out that Bartlett, who weighs 230 pounds, displayed one of the “major risk factors” for the cancer: obesity.

DuPont also contends that C8 isn’t as toxic as the plaintiffs claim. As evidence, Mace cited a report produced by the West Virginia Department of Environmental Protection, with the help of an industry-funded group and several DuPont employees, that set a temporary standard for drinking water safety that was 150 parts per billion (ppb). Yet the company’s own internal standard for the chemical was 1 ppb.

The DuPont lawyer also told the jury about a study the company conducted that concluded Wilbur Tennant, the West Virginia farmer who sued DuPont over the death of his entire herd of cattle, was responsible for his own cows’ deaths. The report failed to disclose that the company had dumped 7,100 tons of C8-contaminated sludge into a landfill near the stream from which Tennant’s cows drank. Instead, the authors blamed Tennant’s “failure to provide the right supplements for the cattle” — a conclusion Mace repeated in court, adding, “They had pink eye and many other issues.”

Wilbur Tennant shot this video in the late 1990s on his property in West Virginia. He died of cancer in 2009; he was 67. This video contains graphic imagery.

If the chemical were really dangerous, DuPont attorneys contend, government agencies would have regulated it. The implication is that the company was within its rights to dump barrels of the stuff into the ocean, as it did in the 1960s. And that it was perfectly fine to emit more than 632,000 pounds of the toxic substance directly into the Ohio River, as DuPont did over the more than 50 years it used C8 in West Virginia. “They were allowed under the law,” Mace said of the plant’s river emissions. “There is a difference between emissions from a plant and what an individual is exposed to. There weren’t people there right at that pipe.”

We’ll soon know which argument a jury finds more persuasive. But even if they decide in Bartlett’s favor, or the company opts to settle the suits, the costs may not fall to DuPont. Facing years of litigation over the chemical and the possibility of federal regulation — and thus enormous cleanup liabilities — in July DuPont spun off its chemical division into a separate company called Chemours.

Settlement costs could force Chemours, whose stock price has fallen 57 percent since June, to the brink of bankruptcy — or beyond.