Visual aids, including drawings and a cupcake analogy, were used to explain causation and whether platform negligence was a substantial factor in Kaley’s harms.

Closing arguments incorporated illustrative visuals and the cupcake analogy to guide jurors on whether each platform’s conduct was a substantial factor and to assess damages if liable.

This bellwether, among several, could shape thousands of similar lawsuits and set liability standards for platforms alleged to harm children.

Outside the courtroom, parents and advocates stressed continued awareness and safety reforms, viewing the proceedings as a symbolic win regardless of the verdict.

The trial faced logistical hiccups, including a juror’s hospitalization and a move to a new building after water damage, while the public focus on Zuckerberg intensified scrutiny over recordings and courthouse camera policies.

Judge Carolyn B. Kuhl instructed jurors on substantial factor causation to guide the deliberations.

In a landmark Los Angeles bellwether trial, Kaley, a 20-year-old plaintiff, accuses Meta (Instagram) and Google (YouTube) of addictive design linked to her mental health harm, with other platforms like Snap and TikTok also involved in related defenses.

The judge told jurors to treat each platform as its own case and to consider damages with the provocative question: what is a lost childhood worth?

A dozen grieving parents attended Zuckerberg’s testimony, using symbolic butterfly clips and ticketed seating to influence public opinion and juror perception.

Testimony spanned addiction experts, therapists, platform engineers, and executives, including Mark Zuckerberg, with closing arguments anticipated after about a month of proceedings.

Closing statements are scheduled at the Spring Street Courthouse after extensive testimony from experts, therapists, engineers, and executives.

Attorneys General from 29 states are pursuing claims against Meta over effects on children’s mental and physical health, signaling broad legal scrutiny beyond the current trial.