This week marks the beginning of a pivotal trial in Los Angeles involving three major tech giants—Meta’s Instagram, ByteDance’s TikTok, and Google’s YouTube—who are accused of intentionally creating addictive platforms that harm children.

The trial, taking place at the Los Angeles County Superior Court, starts with jury selection. This marks the first occasion these companies will present their defense before a jury, a scenario that could significantly impact their operations and future interactions with young users. The jury selection is anticipated to last several days, with 75 potential jurors being evaluated daily until at least Thursday. Snap Inc., the parent company of Snapchat and initially a part of this lawsuit, reached a settlement last week, the terms of which remain confidential.

The lawsuit centers around a 19-year-old referred to as “KGM,” whose case could set the precedent for numerous similar lawsuits against social media firms. KGM, along with two other individuals, has been chosen for bellwether trials. These trials serve as preliminary tests to gauge how arguments might hold up in court and to assess potential damages, explained Clay Calvert, a senior fellow specializing in technology policy at the American Enterprise Institute.

KGM asserts that her early use of social media led to addiction and worsened her depression and suicidal tendencies. The lawsuit contends that the companies intentionally designed their platforms to be addictive for children, aiming to increase profits. If this argument prevails, it could bypass the companies’ usual defenses under the First Amendment and Section 230, which generally shield tech firms from liability regarding content on their platforms.

The lawsuit argues that the defendants used techniques similar to those employed by slot machines and the tobacco industry, embedding design features that maximize youth engagement to enhance advertising revenue.

Executives, including Meta CEO Mark Zuckerberg, are expected to testify at the trial, which will last six to eight weeks. Experts have drawn similarities to the Big Tobacco trials that led to a 1998 settlement requiring cigarette companies to pay billions in health care costs and restrict marketing targeting minors.

“Plaintiffs are not merely the collateral damage of Defendants’ products,” the lawsuit says. “They are the direct victims of the intentional product design choices made by each Defendant. They are the intended targets of the harmful features that pushed them into self-destructive feedback loops.”

The tech companies dispute the claims that their products deliberately harm children, citing a bevy of safeguards they have added over the years and arguing that they are not liable for content posted on their sites by third parties.

“Recently, a number of lawsuits have attempted to place the blame for teen mental health struggles squarely on social media companies,” Meta said in a recent blog post. “But this oversimplifies a serious issue. Clinicians and researchers find that mental health is a deeply complex and multifaceted issue, and trends regarding teens’ well-being aren’t clear-cut or universal. Narrowing the challenges faced by teens to a single factor ignores the scientific research and the many stressors impacting young people today, like academic pressure, school safety, socio-economic challenges and substance abuse.”

A Meta spokesperson said in a statement Monday the company strongly disagrees with the allegations outlined in the lawsuit and that it’s “confident the evidence will show our longstanding commitment to supporting young people.”

José Castañeda, a Google Spokesperson, said Monday that the allegations against YouTube are “simply not true.” In a statement, he said “Providing young people with a safer, healthier experience has always been core to our work.”

TikTok did not immediately respond to a request for comment Monday.

The case will be the first in a slew of cases beginning this year that seek to hold social media companies responsible for harming children’s mental well-being. A federal bellwether trial beginning in June in Oakland, California, will be the first to represent school districts that have sued social media platforms over harms to children.

In addition, more than 40 state attorneys general have filed lawsuits against Meta, claiming it is harming young people and contributing to the youth mental health crisis by deliberately designing features on Instagram and Facebook that addict children to its platforms. The majority of cases filed their lawsuits in federal court, but some sued in their respective states.

TikTok also faces similar lawsuits in more than a dozen states.