IN RE: SOCIAL MEDIA ADOLESCENT ADDICTION/PERSONAL INJURY PRODUCTS LIABILITY LITIGATION
Issue
In *In re Social Media Adolescent Addiction/Personal Injury Products Liability Litigation*, Meta Platforms argues that five witnesses it intends to call at trial were timely and adequately disclosed under the applicable pretrial schedule, and that the State Attorneys General's motion to strike those witnesses mischaracterizes the disclosure record. A secondary question runs in parallel: whether the AGs' own supplemental filing (ECF 3104), submitted without apparent leave of court, was itself procedurally improper and subject to being stricken. Both questions turn on how strictly the MDL court is enforcing its case management orders as trial approaches.
What Happened
Meta filed this notice on June 4, 2026, in the Northern District of California MDL, in response to the State AGs' motion to strike five Meta witnesses from Meta's trial witness list (ECF 3056) and the AGs' subsequent supplemental filing on that motion (ECF 3104). Although styled as a "Notice of Filing Follow-Up Materials," the document functions substantively as a supplemental brief in support of Meta's earlier opposition (ECF 3060-1), accompanied by 22 exhibits and a declaration from Meta's counsel Ashley M. Simonsen authenticating those exhibits. The exhibits are offered to establish the communications, correspondence, and prior filings that Meta contends demonstrate both adequate witness disclosure and the AGs' procedural overreach. Embedded within the notice, Meta also affirmatively requests that the Court strike ECF 3104 on the ground that the AGs filed additional argument without leave, in violation of local rules and the Court's briefing schedule. Meta's position is that striking its witnesses on the eve of trial would impose disproportionate prejudice given the existing discovery record, while the AGs' unauthorized supplemental brief compounds that unfairness by injecting new arguments outside the agreed schedule.
Why It Matters
This filing is a procedural skirmish, not a substantive legal development, but it carries practical significance for how the trial will unfold: whether five Meta witnesses survive or are stricken will directly shape the evidentiary landscape at trial. The mutual accusations of improper supplemental filing — each side effectively doing what it accuses the other of doing — illustrate how pre-trial witness disputes in complex MDLs can become procedural warfare that runs independent of the underlying merits. The Court's response will serve as a reliable signal of how tightly it intends to enforce case management discipline in the final stretch before trial, and practitioners monitoring this MDL should treat the ruling as an early indicator of the judge's trial-phase posture rather than as doctrinal output.
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