Meta CEO Mark Zuckerberg is set to testify on Wednesday in a landmark social media addiction trial in California, as lawyers for a young plaintiff argue that Instagram and other platforms were deliberately designed to hook young users.
The 41-year-old tech billionaire, whose company owns Facebook, Instagram and WhatsApp is expected to be the most closely watched witness in the case. The trial is the first in a series of lawsuits that could set a legal benchmark for thousands of similar claims filed by American families against major social media companies.
It will also mark the first time Zuckerberg addresses the safety of Meta’s platforms directly before a jury.
The case centers on whether Instagram and Google-owned YouTube bear responsibility for the mental health struggles of Kaley G.M., a 20-year-old California resident who has used social media heavily since childhood. She began using YouTube at age six, Instagram at 11, and later TikTok and Snapchat.
Jurors in Los Angeles will hear arguments through late March as they consider whether the companies intentionally designed their platforms through algorithms, personalization tools and engagement features to encourage compulsive use among minors.
The proceedings focus exclusively on platform design, since US law largely shields tech companies from liability over user-generated content. TikTok and Snapchat, which were also named in the complaint, reached confidential settlements with the plaintiff before the trial began.
The case, along with two similar trials scheduled for later this year, is seen as a test of whether courts will hold social media companies accountable for what critics describe as a youth mental health crisis marked by rising rates of depression, anxiety, eating disorders and suicide.
Instagram chief Adam Mosseri testified earlier this month, rejecting the term “addiction” in favor of what Meta calls “problematic use.”
“I’m sure I’ve said that I was addicted to a Netflix show when I binged it really late one night, but I don’t think that’s the same thing as clinical addiction,” Mosseri told the court.
The testimony drew emotional reactions from families in attendance, including mothers whose teenage children had died by suicide.
Psychiatrist Anna Lembke also testified, describing social media as a potential “gateway drug” that can rewire developing adolescent brains toward addictive behaviors.
Court documents revealed internal debates within Meta over controversial features such as cosmetic surgery filters. Despite warnings from some executives about potential harm to teenage girls, Zuckerberg approved their reinstatement in 2020 amid concerns about competition from TikTok.
YouTube CEO Neal Mohan had been expected to testify, though plaintiff lawyers said another executive would instead take the stand.
The Los Angeles case runs parallel to a broader federal lawsuit in Oakland, California, which could go to trial in 2026. Separately, Meta faces another trial in New Mexico, where prosecutors allege the company prioritized profits over protecting minors from sexual exploitation.
The outcome of these cases could significantly reshape the legal landscape for social media platforms in the United States.
