Source: Sara Randazzo

In a San Francisco courtroom this month, a jury will be asked to weigh a complicated question: Did Roundup weedkiller cause a man’s cancer?

The jurors will assess the credibility of competing studies that delve into cell mutations, cancer epidemiology and genotoxicity. They’ll hear evidence purporting to show why California resident Edwin Hardeman’s exposure to Roundup was dangerous, and other analyses arguing it was perfectly safe.

But unlike in a prior trial brought against the herbicide’s maker, Bayer AG, the jurors won’t simultaneously hear allegations that the company hid dangers about its product from the public. Instead, they’ll take part in an unusual split trial focused first on the science, and then, only if they find the plaintiff’s claims valid, on the question of negligence.

A federal judge approved a request by the company for this slimmed-down trial, over the objection of the plaintiff’s lawyers, to let the jury evaluate the alleged dangers of Roundup without what he called the significant distraction of attacks on the company’s behavior.

The approach is the latest attempt by courts to resolve a long-running debate over how to ensure the fairest decisions in cases concerning complicated science. The results could influence hundreds of similar Roundup cases—and guide judges in other cases that hinge on science.