Facebook parent company Meta is facing a landmark courtroom test in California, where a coalition of US states accuses the tech giant of designing Facebook and Instagram to be addictive for children and misleading the public about the risks.

The case, brought by dozens of attorneys general, has been narrowed for trial to four states: California, Colorado, Kentucky and New Jersey, which are acting as representatives for the broader coalition. Their lawyers argue that Meta violated state and federal laws by prioritizing growth and engagement over the mental health and safety of young users.

Pretrial maneuvering has already been intense. Meta recently tried to block testimony from former executive Arturo Bejar, a key whistleblower who has previously criticized the company’s handling of user safety. The judge rejected Meta’s attempt, calling it a last-ditch effort to remove a powerful witness. Bejar is expected to testify about internal discussions on safety, growth and what Meta allegedly knew about harms to young people.

Another flashpoint is the proposed testimony of academic expert Colin Gray, whom the states plan to question about “dark patterns” – interface designs that subtly steer users toward choices that benefit the company. Meta has asked the court to limit the scope of his evidence, arguing that it goes too far.

Meta founder and chief executive Mark Zuckerberg is among the high-profile witnesses expected to take the stand. The states say they will seek about 200 billion dollars in penalties and remedies, far below the trillion-dollar figure Meta cited in earlier filings, which state lawyers describe as an attempt at “shock value.”

Beyond money, the states want structural changes to Meta’s platforms, including restrictions on features they say fuel compulsive use by children. The trial will be decided by the judge, with guidance from an advisory jury of eight people selected after detailed questioning about their own social media use and views on its impact on mental health.

Legal scholars say the case could mark a turning point for the tech industry, drawing comparisons to the 1990s tobacco litigation that forced cigarette makers to pay massive settlements and change their marketing. Experts note that, like tobacco, the Meta case centers on what a powerful company knew internally versus what it told the public – and whether it can be compelled to overhaul its business model as a result.