Developing: Mark Zuckerberg Takes the Stand as Landmark Social Media Addiction Trial Tests Silicon Valley's Legal Shield

The trial's opening statements set the tone for what promises to be a six-to-eight-week legal battle characterized by starkly opposing narratives. Lead plaintiff attorney Mark Lanier told jurors the case was 'as easy as ABC,' which he said stands for 'addicting the brains of children.' He described Meta and Google as 'two of the richest corporations in history' that had 'engineered addiction in children's brains' through deliberate design choices.

Lanier presented the jury with a trove of internal company documents, emails, and studies. Among the most damaging was 'Project Myst,' an internal Meta survey of 1,000 teens and their parents that reportedly found two key conclusions: children who experienced adverse events like trauma and stress were particularly vulnerable to addiction, and parental supervision and controls made little meaningful impact. Lanier also introduced internal Google documents that likened YouTube to a casino and communications between Meta employees in which one described Instagram as 'like a drug,' adding that employees were 'basically pushers.'

The plaintiff, KGM — who is now 20 years old and from California — alleges she began compulsively using YouTube at age 6 and started scrolling Instagram around age 9. Before she finished elementary school, she had posted 284 videos on YouTube. Her attorneys claim that her use of the platforms worsened her depression and suicidal thoughts through features including infinite scroll, auto-play, beauty filters, likes, and push notifications — all deliberately designed to make the apps impossible to put down.

Meta and Google have mounted a vigorous defense, arguing that the lawsuits dangerously oversimplify a complex mental health landscape and that social media has become a convenient scapegoat for the multifaceted emotional challenges children face. Paul Schmidt, one of Meta's attorneys, told jurors in his opening statement that the company does not dispute KGM experienced mental health struggles — but that Instagram was not a substantial factor. He pointed to medical records showing a turbulent home life, arguing that KGM turned to social media as a coping mechanism rather than being harmed by it.

A Meta spokesperson stated that the company 'strongly disagrees with the allegations' and is 'confident the evidence will show our longstanding commitment to supporting young people.' In a recent blog post, Meta argued that '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.' José Castañeda, a Google spokesperson, called the allegations against YouTube 'simply not true,' adding that 'providing young people with a safer, healthier experience has always been core to our work.'

The defense strategy also found some support in the testimony of Adam Mosseri, Instagram's head, who appeared as the first high-profile executive to take the stand. Mosseri drew a distinction between 'clinical addiction' and 'problematic use,' maintaining that even seemingly excessive use of social media does not necessarily constitute addiction. When confronted with the fact that KGM had logged 16 hours of Instagram use in a single day, Mosseri called it 'problematic use' but stopped short of labeling it addiction. He also acknowledged not being an 'expert in addiction' when pressed repeatedly by Lanier.

Perhaps the most explosive element of the trial has been the parade of internal documents that plaintiffs say reveal a stark gap between what social media companies said publicly about child safety and what their own employees were warning internally. Among the communications presented to jurors was a 2019 email exchange between Meta executives discussing the potential harm of beauty filters that allowed users to alter their physical appearance in photos.

Nick Clegg, Meta's former head of global affairs and a former UK Member of Parliament, was among those who raised concerns. In the email, Clegg warned that Meta would end up 'rightly accused of putting growth over responsibility,' which would have a 'regressive' impact on the company's reputation. Mosseri testified that the firm ultimately decided to ban image filters that went beyond mimicking the effects of makeup — but when challenged by Lanier, he admitted the ban had been 'modified,' while denying it had been lifted completely.

Plaintiffs' attorneys also highlighted an internal Meta survey of 269,000 Instagram users in which 60% reported having seen or experienced bullying in the previous week. Lanier noted that KGM herself had made more than 300 reports to Instagram about bullying on the platform — a fact Mosseri said he had not been aware of. The lawsuit draws explicit parallels to the Big Tobacco litigation of the 1990s, alleging that social media companies 'borrowed heavily from the behavioral and neurobiological techniques used by slot machines and exploited by the cigarette industry' to maximize youth engagement and advertising revenue.

For decades, Silicon Valley has operated under the legal umbrella of Section 230 of the Communications Decency Act, the 1996 law that shields tech companies from liability for content posted by users on their platforms. This trial represents a novel and potentially groundbreaking attempt to circumvent that protection entirely. Rather than suing over user-generated content, the plaintiffs have framed their case under product liability law — arguing that the platforms themselves are defective products, much like a car with faulty brakes or a pharmaceutical with dangerous side effects.

The argument is that it is not what users posted that caused harm, but the design features embedded in the platforms — infinite scroll, algorithmic recommendations, notification systems, and engagement-maximizing interfaces — that were engineered to be addictive. If successful, this legal theory could fundamentally alter the relationship between tech companies and the courts, opening the door to liability claims that Section 230 was never intended to address.

Under California state court rules governing this trial, the jury needs a three-fourths agreement — 9 out of 12 jurors — to rule for either side. A victory for KGM could result in significant monetary damages and, more importantly, court-ordered changes to how social media platforms operate. Legal experts widely expect that the trial's outcome will catalyze settlement negotiations for the hundreds of other pending lawsuits, including a federal bellwether trial set for June in Oakland representing school districts, and more than 40 state attorneys general lawsuits filed against Meta across the country.

Beyond the legal arguments, the trial has become a gathering point for a growing movement of families who say their children were harmed or killed as a result of social media. Julianna Arnold, a founding member of the parent advocacy group Parents RISE!, has attended the proceedings in Los Angeles. Her daughter died at 17 after being lured by a predator she met on social media — the man gave her what she believed was a Percocet for her anxiety, but it was fentanyl. 'We lost our kids, and there's nothing we can do about that,' Arnold told NPR. 'But what we can do is inform other parents and families about these harms and that these platforms are dangerous and that we need to put guardrails on these companies.'

Mariano Janin, who traveled from London to witness the trial, stood outside the courthouse holding a photo of his daughter Mia, who died by suicide in 2021 at 14 years old. 'If they changed their business model it would be different,' Janin told the BBC. 'They should protect kids. They have the technology; they have the funds.' Arnold described seeing her own daughter spiral from ages 12 and 13 onward, spending increasing time on her phone, quitting sports, and struggling at school. Parental controls, she said, were 'a workaround — a Band-Aid' that children quickly learned to circumvent.

The trial is also unfolding against a broader global backdrop of regulatory action. France recently approved legislation banning social media for children under 15, Australia has enacted similar age-based restrictions, and India is currently discussing age-based social media limitations with tech firms. In the United States, a separate trial in New Mexico is simultaneously underway, brought by the state's attorney general accusing Meta of failing to prevent child sexual exploitation on its platforms. Sacha Haworth, executive director of the nonprofit Tech Oversight Project, said the Los Angeles case is 'only the first' of what promises to be a watershed year of legal reckoning for Big Tech.