Opening statements began on Feb. 9 in a landmark trial accusing two of the world’s largest social media companies of deliberately designing their platforms to be addictive, and seeking to hold them accountable for alleged harms to children using their technology.

Plaintiffs allege that Meta, Instagram’s parent company, and Google’s YouTube have intentionally designed their platforms to addict and harm minors. TikTok and Snap Inc.—which owns Snapchat—settled for undisclosed amounts after originally being named in the same lawsuit.

Lawyers representing the plaintiffs and the two remaining social media companies named as defendants are offering two contrasting arguments as the case began at the Spring Street Courthouse in downtown Los Angeles on Monday.

Attorney Mark Lanier started first, arguing for the plaintiffs that Meta and Google are “two of the richest corporations in history” who have “engineered addiction in children’s brains.” He suggested the case is as “easy as ABC,” or what he described as standing for “addicting the brains of children.”

The case centers on a 19-year-old named only with the initials “KGM,” and could have widespread implications for similar lawsuits accusing social media companies of harm.

“KGM” and two other plaintiffs were selected for these bellwether trials, which amount to test cases determining how the arguments for both sides will play out before juries and what damages, if any, might be awarded, according to Clay Calvert, a nonresident senior fellow of technology policy studies at the American Enterprise Institute.

The current trial is the first time Meta and Google are arguing their cases in front of a jury, with potential lasting impacts on both their businesses and how they will have to handle child access to their platforms in the future.

“KGM” was a minor when she allegedly became addicted to social media platforms. She claims they had a damaging impact on her mental health, leading to increased depression and suicidal ideation. Her lawsuit accuses the companies of making deliberate design choices to tailor their platforms to be more addictive to minors in an effort to increase revenue.

If her case is successful, it could bypass the tech giants’ First Amendment protections and Section 230, which shields tech companies from any liability derived from material on their platforms.

“Borrowing heavily from the behavioral and neurobiological techniques used by slot machines and exploited by the cigarette industry, Defendants deliberately embedded in their products an array of design features aimed at maximizing youth engagement to drive advertising revenue,” the lawsuit alleges.

Lanier argued on Monday that Meta and Google will “try to blame the little girl and her parents for the trap they built,” referring to “KGM.”

He also contested the companies’ public position that they try to protect minors and introduce safeguards within their platforms, pointing to internal documents that illustrate a different picture, which have references to young children being within their target audiences.

Lanier went further, accusing the tech giants of engineering a “feature that caters to a minor’s craving for social validation,” referring to the platforms’ “like” buttons and related features.

“For a teenager, social validation is survival,” he said.

The court went into recess for lunch before the plaintiffs finished their opening statement, and before attorneys representing Meta and Google could offer theirs.

Meta strongly disagrees with the lawsuit’s allegations and is “confident the evidence will show our longstanding commitment to supporting young people,” a spokesperson for the company said in a recent statement.

Google spokesperson José Castañeda defended YouTube in a statement and said the allegations are “simply not true.”

“Providing young people with a safer, healthier experience has always been core to our work,” he said.

The trial, which is expected to last six to eight weeks, could see testimony from Meta CEO Mark Zuckerberg. Experts have compared the case to one against Big Tobacco that resulted in a 1998 settlement that forced multiple companies to pay billions in medical care expenses and cease targeted marketing to minors.

The Associated Press contributed to this report.