A jury will hear closing arguments Thursday in a landmark trial examining whether social media companies should be held liable for harms caused to children using their platforms. The case is being heard at the Spring Street Courthouse in Los Angeles after about a month of testimony from addiction experts, therapists, platform engineers and executives.

The plaintiff, identified as KGM or Kaley, is a 20-year-old woman who alleges her early use of social media addicted her to the technology and worsened depression and suicidal thoughts. She is suing Meta and Google-owned YouTube, the remaining defendants after TikTok and Snap settled before trial began.

The case serves as a bellwether trial, meaning its outcome could influence how thousands of similar lawsuits against social media companies proceed. Meta CEO Mark Zuckerberg testified during the proceedings, which featured testimony from various experts and company representatives.

Both sides have acknowledged the plaintiff experienced a turbulent home life. Her attorneys argue she was targeted as a vulnerable user, while defense lawyers contend she turned to social media platforms as a coping mechanism for pre-existing mental health struggles.

Meta's legal team, led by lawyer Paul Schmidt, has argued that Kaley faced significant challenges before using social media and questioned whether the platforms were a substantial factor in her mental health issues. YouTube's attorneys have taken a different approach, arguing their platform is not a social media site and that its features are not addictive.

The trial represents one of three selected bellwether cases that could shape the legal landscape for similar litigation against social media companies nationwide.