Three of the world’s tech giants are gearing up to face a pivotal trial in Los Angeles this week. Meta’s Instagram, ByteDance’s TikTok, and Google’s YouTube are at the center of accusations that their platforms intentionally foster addiction and harm among children.

Kicking off in the Los Angeles County Superior Court, the jury selection process for this landmark trial is underway. For the first time, these companies will present their defense before a jury, a process that could substantially impact their operations and policies regarding young users. The jury selection is anticipated to span several days, with 75 potential jurors evaluated each day through at least Thursday. Notably, Snap Inc., the parent company of Snapchat and another defendant in the lawsuit, reached a settlement last week for an undisclosed amount, opting out of the trial.

The case centers around a 19-year-old referred to as “KGM,” whose experience may influence the outcomes of numerous similar cases against social media companies. KGM, along with two other plaintiffs, has been chosen for bellwether trials—these are essentially test cases providing insights into how a jury might respond to arguments and potential damages, explained Clay Calvert, a senior fellow in technology policy studies at the American Enterprise Institute.

KGM alleges that early exposure to social media led to addiction, worsening her depression and suicidal thoughts. The lawsuit contends that this was the result of deliberate design choices by the companies, aimed at making their platforms more addictive to young users for profit maximization. If this argument prevails, it could challenge the protections these companies usually enjoy under the First Amendment and Section 230, which typically shields tech firms from liability for user-generated content.

The lawsuit argues that the companies employed techniques akin to those used in slot machines and by the cigarette industry. These strategies include embedding design features intended to maximize youth engagement, thereby driving advertising revenue, according to the lawsuit.

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 healthcare 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.”

Meta, YouTube and TikTok did not immediately respond to requests 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.