LOS ANGELES, California: Three of the world's largest social media companies are set to face a jury in Los Angeles this week in a closely watched trial that could reshape how tech platforms are held accountable for the impact of their products on children.

Meta, TikTok owner ByteDance, and YouTube will defend themselves against claims that their platforms deliberately addict young users and harm their mental health. Jury selection begins this week in Los Angeles County Superior Court and is expected to last several days, with dozens of potential jurors questioned daily.

The case marks the first time the companies will argue such claims before a jury. Legal experts say the outcome could have wide-ranging implications for the tech industry and how companies design products used by children.

A fourth defendant, Snap Inc., which owns Snapchat, settled the case last week for an undisclosed sum.

At the center of the trial is a 19-year-old plaintiff identified only as "KGM," whose case could shape the fate of thousands of similar lawsuits pending against social media companies. KGM and two other plaintiffs were selected for bellwether trials — test cases meant to gauge how juries respond to the legal arguments and potential damages, said Clay Calvert, a nonresident senior fellow of technology policy studies at the American Enterprise Institute.

KGM alleges that her early and prolonged use of social media led to addiction and worsened depression and suicidal thoughts. Crucially, the lawsuit argues that this harm resulted from deliberate design choices intended to increase youth engagement and maximize profits — a legal strategy that could bypass protections typically afforded to tech companies under the First Amendment and Section 230.

"Borrowing heavily from the behavioral and neurobiological techniques used by slot machines and exploited by the cigarette industry, Defendants deliberately embedded in their products an array of design features aimed at maximizing youth engagement to drive advertising revenue," the lawsuit says.

Executives, including Mark Zuckerberg, are expected to testify during the six- to eight-week trial. Observers have compared the proceedings to the Big Tobacco litigation that culminated in a 1998 settlement forcing cigarette makers to pay billions in healthcare costs and restrict marketing to minors.

"Plaintiffs are not merely the collateral damage of Defendants' products," the lawsuit says. "They are the direct victims of the intentional product design choices made by each Defendant. They are the intended targets of the harmful features that pushed them into self-destructive feedback loops."

The companies deny the allegations, pointing to safeguards added over the years and arguing they are not responsible for content posted by third parties.

"Recently, a number of lawsuits have attempted to place the blame for teen mental health struggles squarely on social media companies," Meta said in a recent blog post. "But this oversimplifies a serious issue. Clinicians and researchers find that mental health is a deeply complex and multifaceted issue, and trends regarding teens' well-being aren't clear-cut or universal. Narrowing the challenges faced by teens to a single factor ignores the scientific research and the many stressors impacting young people today, like academic pressure, school safety, socio-economic challenges, and substance abuse."

Meta, YouTube, and TikTok did not immediately respond to requests for comment.

The trial is the first in a wave of cases scheduled this year seeking to hold social media companies responsible for harms to children's mental health. A federal bellwether trial representing school districts is set to begin in June in Oakland, California.

More than 40 U.S. state attorneys general have also sued Meta, alleging it contributes to the youth mental health crisis through addictive design features on Instagram and Facebook. TikTok faces similar lawsuits in more than a dozen states.