Paul Singh Grewal, deputy general counsel at Facebook. Jason Doiy / The Recorder

SAN FRANCISCO — A top in-house lawyer at Facebook Inc. said Thursday the company is in a complicated game of cat and mouse with purveyors of “fake news” as it seeks to curb the spread of misinformation via its social media platform.

“Teasing out the false viral story from the true or accurate viral story is no small challenge,” said Facebook Deputy General Counsel Paul Grewal, speaking on a panel that closed out the Ninth Circuit Judicial Conference Thursday morning. “There is important economic and financial underpinning under this that are just as critical at getting to the bottom of as” the technological questions, Grewal said.

Grewal, who left his position as a U.S. magistrate judge in the Northern District of California last year to join Facebook, spoke on a panel titled “Lies, Damn Lies, and the News? Fake News: What It Is, What It Means, and Why It Matters.” He was joined NBC Universal News Group general counsel Susan Weiner, Slate magazine’s Dahlia Lithwick, and conservative columnist and radio host Hugh Hewitt. The conversation was moderated by Kathleen Hall Jamieson, director of the Annenberg Public Policy Center of the University of Pennsylvania.

Grewal told audience members that Facebook’s approach to slowing the spread of fake news on its site has involved disrupting the economic incentives of fake news producers who seek to draw eyeballs to their sites to boost revenues through advertisements, subscriptions or purchases. Grewal said Facebook also made it more difficult for sites to post web addresses that mimic legitimate news outlets that could mislead readers about the source of a particular story.

Facebook has been developing new ways to identify and flag fake news content. Facebook now alerts users before they share items that others have marked as suspect and unreliable. The site has also partnered with fact-checking organization such as PolitiFact, the Associated Press and factcheck.org to review stories as part of the process.

Grewal pointed out that the German legislature has given regulators the authority to fine parties responsible for spreading misinformation.

“Even without legislation there are strong incentives to get this right,” Grewal said. “Consumer trust is paramount.”

Grewal said he thinks it would be counterproductive to shut down users ability to share fake news stories altogether. “The answer is not simply to shut down the speech,” he said. “I don’t think that’s where we want to be as a country, I don’t think that’s where we want to be as a society.”

Ross Todd is bureau chief of The Recorder in San Francisco. He writes about litigation in the Bay Area and around California. Contact Ross at rtodd@alm.com. On Twitter: @Ross_Todd.