Image source, State of California Department of Justice

The BBC's Lily Jamali asks California AG Rob Bonta about estimates that Meta could have to pay $1.4 trillion if it loses this case.

"We are not asking for $1.4 trillion," Bonta answers, adding that number was one which Meta had used when talking about the case.

"We will be asking for a significant financial payment" for civil penalties not damages, he says. "The judge will determine that."

The press conference with the attorney generals has now finished.

Image source, Reuters

When asked if Meta CEO Mark Zuckerberg will testify in the trial, California AG Bonta says that is "unknown" at this point.

He points out that Zuckerberg has testified in other cases, but whether he does here "is still TBD".

Bonta says he has no personal preference if the Meta boss shows up or not.

Colorado Attorney General Phil Weiser is now speaking. He begins by talking about one mother in court today whose teenage daughter died by suicide "after sustained exposure and engagement" on social media.

He says the teenage girl spent many hours online, and had a social media addiction "watching videos that harmed her," adding she received guidance online not to talk to her parents about her mental health.

He says the girl's mother fought through that pain and "found purpose" to fight for the families of other children.

"This social media-fuelled youth mental health crisis demands action," he says.

Bonta says Meta chose profits over the safety of users.

The company's conduct is "illegal", he alleges, adding it had a legal and moral obligation to make products safe for young users.

"If you are a parent... sadly you have likely seen some of this play out in your own life."

Image source, Reuters

Bonta's team has proof that Meta knows "Instagram is harmful to a significant percentage of teenagers, including teen girls,” the attorney general says.

He adds that Meta knows about instances of self harm and eating disorders sparked by the platform.

Bonta also accuses Meta of being aware that the "like" button causes teenagerss to compulsively engage with Instagram.

California Attorney General Rob Bonta says this trial will last five to seven weeks.

Both sides laid out their cases today, he says, adding that the states' case was particularly "compelling" with their first witness speaking of Meta knowing about harm to its users but failing to act.

Meta's motto was to "move fast and break things", he says, adding, "Unfortunately, the thing that was broken here was the mental health of our children."

California Attorney General Rob Bonta opens his statements by thanking his colleagues who have helped bring this case, describing it as a "collaborative effort" between the 29 states involved.

Attorneys general from the states bringing this case agianst Meta are speaking to the press now, following the first day of arguments in court.

You can watch live at the top of this page.

Sakshi Venkatraman
US reporter

This is one of the biggest legal challenges to ever face Meta -- and its effects could change the landscape of social media permanently, says James Grimmelmann, a professor of digital and information law at Cornell University.

If the plaintiffs prevail, there will likely be billions of dollars in damages and major structural changes to Meta. That could "add up, even for a company of Meta's size," Grimmelman says.

But the impacts may even be felt beyond Meta itself.

"This very well could have ripple effects for a lot of platforms... all of them have their own slice of concerns they could be targeted with," he says. "The core idea that you could be held liable for interface and design... that cuts across the entire set."

Grimmelmann adds that it's hard to know how Meta will tackle the issues the plaintiffs set out over the course of the trial, especially because several Meta employees are being called up to the stand by the plaintiffs. We're also not sure what the evidence will be.

"Lots of this stuff hasn't really been extensively discussed in public," he says.

But ultimately, if Meta doesn't prevail here, one thing is clear: "Kids could have very substantially reduced access to social media."

Not only will Meta be forced to remove the features that are "most appealing" to an audience of minors, but legislation outside of this lawsuit may limit their access altogether.

We've been following today's proceedings mainly via a livestream from the courthouse.

That livestream provided by the court has just abruptly stopped, mid-testimony.

We are now hearing the attorneys general from the states bringing the lawsuit will hold a briefing with media in about 30 minutes.

Meta whistleblower Arturo Béjar references a 2021 social media post from Meta CEO Mark Zuckerberg Zuckerberg in which the leader said Meta does not prioritise profit over the safety and well-being of its users.

Béjar says thought Zuckerberg's post was creating a false and misleading impression of Facebook's commitment to safety and the well-being of young people.

That post from Zuckerberg prompted Béjar to send the Meta boss an email alerting him of the amount of harm that people were reporting they were experiencing on the platform.

The lawyer then asks Meta whistleblower Arturo Béjar about attempts he made to raise safety issues as he saw them. He shows the jury a chain of emails from Béjar to Chris Cox, who Bejar describes as "Mark Zuckerberg's right hand man".

"I was trying to communicate... how big the gap was between what users were telling the company was harm that they were experiencing versus what the company was prioritising on and communicating to the public about harm."

Again Béjar, tells the court that prevalence of policy-violating content is not the same thing as someone experiencing harm, and is a "very narrow measure of a very specific thing".

Béjar says whenever Mark Zuckerberg was asked about harm internally, he would immediately start talking about prevalence, which made him think this was how Zuckerberg thought about the concept.

"His [Cox's] response to this was very kind and then laying out the groundwork for eventually bringing it up to Mark and the belief that they didn't know how bad the harm was and that was the reason that the company was acting the way it did."

Arturo Béjar says Meta's community standards report - in which it publishes statistics on the prevalence of harmful content across its platforms - under-counts the prevalence of such content.

For example, he says, Meta reported that the risk of teens being exposed to graphic or violent content was 0.01 to 0.02%.

But Meta also had user survey results - that it did not publish - showing that the prevalence of graphic or violent content was actually 100 to 400 times higher than the reported number, Béjar says.

Béjar is now being asked to review a Meta report in which the tech company says it measures harm on Facebook by the prevalence of content that violates its standards.

When asked if he agrees with that metric, the witness emphatically responds "no".

"Harm is what people experience as harm," he says, giving the example of a thirteen year old child reporting distress and asking for help. "Prevalence is a very narrow measure of a very specific thing."

He adds: “I wanted to bring up at every layer of management an awareness of the level of harm people were experiencing that was a result of the way the product was designed - and that was preventable in our experience."

Béjar says that Instagram changed from a product that you use "to a product that uses you".

He says that at first it only showed you photos of people that you followed, with natural stopping points and users in control of their experience.

He says that it went from being a product where a person has control to one where you don't, and people users connected with were "primarily strangers".

He says that is a change that brings "substantial risks and issues".

Béjar is asked about the period between when he left Facebook in 2015 and returned in 2019 and what made him want to return.

He says his daughter was 14 when he allowed her to set up an Instagram account, but: "Shortly after she went on, she started getting requests for sex and pictures of private parts from people she did not know."

He says that when he asked his daughter if she had reported it, he was told there was no option to do this. "I just block them and they laugh it off and they just move on to the next person," he recounts his daughter telling him.

He says he thought something had "broken or was not working" in the company and he wanted to address it with them, instead of criticising from the sidelines.

Béjar is asked if he believes Meta used its research to improve wellbeing.

He says research was not "effectively" used, adding that Meta detected "significant number of harms including harms to young people” but did not make changes based on these findings.

Béjar says that around the 2019 to 2021 period, Meta had the mantra "move fast and break things". This communicated to employees that their goal was to get things into the hands of users as quick as possible, Béjar says, while safety and security was an "afterthought".

When asked about his interactions with Meta executives, Béjar says his role involved him interacting regularly with Mark Zuckerberg, including when there were issues or incidents that required the CEO's attention. Béjar estimates speaking to Zuckerberg at least 100 times.

Meta whistleblower Arturo Béjar, former senior engineering and product leader at Facebook, is the first witness.

Béjar says he will talk about his experience at the company, including concerns he brought to leadership as well as his role testing Meta's safety features, which he found to be ineffective.

He adds that Meta took a "don't ask, don't tell approach" to kids under 13 being on the platform.

Wrapping up the opening arguments for Meta, Schmidt addresses the idea that social media is addictive, particularly for young people.

“There can be no dispute that Meta has recognised people struggle, or can struggle, with their use of social media, and has come up with tools to try and address that,” Schmidt says.

However, he points to past statements from Mark Zuckerberg and Adam Mosseri that not only were Facebook and Instagram not designed to be addictive, scientific research has not yet come to support the idea that an addiction to social media is possible.

Meta has pushed back repeatedly in past litigation this year on the idea that social media addiction exists.

Schmidt also indicates that the states pursuing the case against Meta have largely failed to prove that the company not only directed Facebook and Instagram to young users and those under 13 years old, but that it knew of specific underage users and did nothing to get them off of the platforms.

He says state attorneys have presented no specific children that they have found that were on Meta’s platforms improperly, and that an expert witness will only be able to show some 150,000 underage users were found to have been on the platforms.

Schmidt says Meta witnesses will say they understood the government didn't require age limits but the company took steps anyway.

Meta will present data that shows 96% of people who use Facebook are adults, and 4% are teens.

Instagram skews more to teens and younger adults, but the data is similar, he says.

How will the attorneys general prove these services are directed to children, he asks.