A landmark US trial against Meta for allegations it deliberately designed Instagram and Facebook to encourage compulsive use among children and teens began Tuesday in a federal court in Oakland, California.

The trial, before US District Judge Yvonne Gonzalez Rogers, stems from a complaint filed by a bipartisan coalition of state attorneys general. The case involves 29 states, including California, Colorado, Kentucky and New Jersey, which are pursuing consumer-protection claims alongside a federal claim under the Children’s Online Privacy Protection Act (COPPA).

California’s Deputy Attorney General Megan O’Neill accused Meta of building its business around keeping users engaged, collecting their data and concealing information about potential risks.

“Facebook and Instagram were designed to keep kids on them and to keep them coming back, even when they knew it was bad for them,” said O’Neill.

She alleged that Meta knew about the vulnerabilities of children’s developing brains and their sensitivity to social feedback, and used that knowledge when designing platform features.

O’Neill said the states would present Meta’s internal research and surveys documenting negative experiences for young users. She also accused the company of restricting access to some of its mental health and well-being research, and preventing additional studies that could have exposed risks.

She said Meta sought to maintain “plausible deniability” and accused it of telling Congress, parents and users that Instagram and Facebook were safe for children while “hiding the truth.”

The case is not aimed at eliminating Instagram, said O’Neill, but at determining whether Meta misled the public, acted unfairly and violated COPPA.

The states allege that features including infinite scrolling, notifications, likes and recommendation algorithms encourage excessive use and contribute to mental and physical health problems among young people.

Meta denies wrongdoing and said it has introduced protections, including Teen Accounts, age-detection technology and parental supervision tools.

An eight-member jury is serving in an advisory capacity after Meta withdrew its demand for a jury trial. Rogers will ultimately determine liability and any remedies.

The trial is expected to last seven weeks. Potential remedies could include tighter age restrictions and changes to platform features and recommendation systems.