A coalition of 29 U.S. states will begin presenting its case against Meta on Tuesday in a California federal court, alleging that Facebook and Instagram were designed in ways that harmed the mental health of children and teenagers.

Attorneys for Colorado, California, New Jersey and Kentucky will deliver opening statements before an eight-person jury in Oakland. The jury will serve in an advisory role, while U.S. District Judge Yvonne Gonzalez Rogers will ultimately decide the case.

The four states leading the case allege that Meta designed Facebook and Instagram to be addictive to young users and misled consumers about the safety of its platforms. All 29 states also accuse Meta of improperly collecting and using children's personal data in violation of federal law.

Meta is expected to argue that it has made significant efforts to protect young users and has not misled consumers about safety. The company has also argued that the states have failed to provide evidence of actual harm to their residents.

Meta founder and CEO Mark Zuckerberg and Instagram head Adam Mosseri are expected to testify during the multiweek trial.

The case could have major financial and regulatory consequences for Meta. The company has said the states could seek penalties of up to $1.4 trillion, while the attorneys general said last week that the amount could be closer to $200 billion.

Colorado, Kentucky, California and New Jersey are also asking the judge to require nationwide changes to Meta's platforms, including age restrictions and an end to infinite scrolling.

The lawsuit, filed in 2023, followed a multistate investigation into the impact of Instagram and Facebook on young users. The states are expected to present internal Meta documents, research and testimony from former employees and experts.

Meta and other social media companies are facing thousands of lawsuits from states, municipalities, school districts and individuals over allegations that their platforms harm young users.