A Los Angeles courtroom is hosting what may become the most consequential legal challenge Big Tech has ever faced.

This is an inflection point in the global debate over Big Tech liability: For the first time, an American jury is being asked to decide whether platform design itself can give rise to product liability – not because of what users post on them, but because of how they were built.

As a technology policy and law scholar, I believe that the decision, whatever the outcome, will likely generate a powerful domino effect in the United States and across jurisdictions worldwide.

The plaintiff is a 20-year-old California woman identified by her initials, K.G.M. She said she began using YouTube around age 6 and created an Instagram account at age 9. Her lawsuit and testimony allege that the platforms’ design features, which include likes, algorithmic recommendation engines, infinite scroll, autoplay and deliberately unpredictable rewards, got her addicted. The suit alleges that her addiction fueled depression, anxiety, body dysmorphia – when someone see themselves as ugly or disfigured when they aren’t – and suicidal thoughts.

TikTok and Snapchat settled with K.G.M. before trial for undisclosed sums, leaving Meta and Google as the remaining defendants. Meta CEO Mark Zuckerberg testified before the jury on Feb. 18, 2026.

The stakes extend far beyond one plaintiff. K.G.M.’s case is a bellwether trial, meaning the court chose it as a representative test case to help determine verdicts across all connected cases. Those cases involve approximately 1,600 plaintiffs, including more than 350 families and over 250 school districts. Their claims have been consolidated in a California Judicial Council Coordination Proceeding, No. 5255.

The California proceeding shares legal teams and evidence pool, including internal Meta documents, with a federal multidistrict litigation that is scheduled to advance in........

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