Lawyers for the plaintiffs argue that Meta intentionally designed its social media platforms to be addictive

The Meta CEO, Mark Zuckerberg, is testifying at a landmark trial of social media companies on Wednesday.

After arriving at the courthouse, Zuckerberg was asked by a security guard at a metal detector if he had any metal on him. “I have a gold chain on,” he responded, according to the New York Post.

Lawyers for the plaintiffs, who argue that Meta intentionally designed its social media platforms to be addictive, have the opportunity to grill Zuckerberg about whether he knew of harms his company’s products could inflict on young people’s mental health. The plaintiffs have already made public internal documents they say prove their point.

This is the first time Zuckerberg is addressing concerns about child safety before a jury at trial. Tech companies have long relied on a federal law that shields them from liability for content posted by users, but the plaintiffs’ novel argument – which is focused on harmful design and not individual actors – has so far sidestepped this defense.