Meta Platforms chief executive Mark Zuckerberg arrived at a Los Angeles court on Wednesday to testify before a jury for the first time over claims that Instagram and YouTube were deliberately engineered to addict children, in what legal experts are calling the most consequential technology trial in a generation.
Zuckerberg, 41, entered Los Angeles Superior Court around 8:30 a.m. local time, walking past grieving parents, journalists and waiting jurors without responding to questions. He faces pointed questioning from attorneys representing Kaley, a 20-year-old California woman identified in court documents by her initials K.G.M., who alleges that compulsive exposure to Meta’s Instagram from the age of nine caused her severe anxiety, body dysmorphia and suicidal thoughts.
The trial, running until late March, is the first among more than 1,600 consolidated lawsuits filed by American families and over 250 school districts against major social media companies. Its outcome is expected to shape the legal fate of thousands of similar claims and determine whether platform design decisions, such as algorithmic recommendation systems and infinite scroll features, can legally constitute defective product engineering.
“Internal documents show that Meta understood the dangers its platforms posed to young people,” plaintiff attorney Matthew Bergman said ahead of Wednesday’s session. “Yet Zuckerberg and Meta pushed forward, choosing features designed to keep kids online longer, even when those choices put children directly in harm’s way.”
Meta and Google’s YouTube are the two remaining defendants after TikTok and Snap reached confidential settlements with the plaintiff before the trial commenced. The central legal argument turns on whether the companies structured their platforms to exploit psychological vulnerabilities in minors, a framing that Meta strongly disputes.
“We strongly disagree with the allegations and are confident the evidence will show our longstanding commitment to supporting young people,” a Meta spokesperson said. The company’s lawyers have attributed Kaley’s mental health struggles primarily to difficult family circumstances rather than social media use.
The proceedings gained wider public attention last week when Instagram head Adam Mosseri testified, rejecting the clinical definition of social media addiction and drawing an emotional reaction from parents of teenagers who died by suicide. Psychiatrist Anna Lembke, called by the plaintiffs, testified that social media can act as a gateway to addictive behaviour by altering brain development in young users.
Zuckerberg is expected to face questions about Instagram’s 2020 decision to retain cosmetic surgery filters despite internal warnings from executives that the filters could damage young girls’ self-image, a decision Mosseri defended during his own testimony.
Separately, Meta is also standing trial in New Mexico, where the state attorney general alleges the company failed to prevent child sexual exploitation on its platforms.
The Los Angeles case runs parallel to a related nationwide proceeding before a federal judge in Oakland, California, which could yield a further trial later in 2026.
