“This case is as easy as A-B-C,” Lanier said as he stacked children’s toy blocks bearing the letters.

He contended the A was for addicting, the B for brains and the C for children.

“They don’t only build apps; they build traps,” Lanier said, saying Meta and YouTube pursued “addiction by design,” making his arguments using props like a toy Ferrari and a mini slot machine.

Meta attorney Paul Schmidt countered in opening remarks to the jury that evidence will show problems with the plaintiff’s family and real-world bullying took a toll on her self-esteem, body image and happiness rather than Instagram.

“If you took Instagram away and everything else was the same in Kaley’s life, would her life be completely different, or would she still be struggling with the same things she is today?” Schmidt asked, pointing out an Instagram addiction is never mentioned in medical records included in the evidence.

The trial before Judge Carolyn Kuhl focuses on allegations that a 20-year-old woman identified as Kaley G.M. suffered severe mental harm because she became addicted to social media as a child.

The case is being treated as a bellwether proceeding because its outcome could set the tone, and the level of payouts to successful plaintiffs, for a tidal wave of similar litigation across the United States.