Concord Music Group, Inc. v. Anthropic PBC
U.S. District Court, Northern District of California · N.D. Cal. · California bar guidance
Verified April 26, 2026
- Citation
- Concord Music Group, Inc. v. Anthropic PBC, No. 5:24-cv-03811 (N.D. Cal. May 23, 2025) (van Keulen, M.J.)
- Decided
- May 23, 2025
Summary
Olivia Chen, a data scientist at Anthropic, filed an expert declaration in support of Anthropic's opposition to a preliminary injunction in this music-publisher copyright suit. A footnote in paragraph 9 contained a citation generated by Claude.ai that named a real journal article but fabricated the title and authors. Plaintiffs' counsel raised the error at a hearing before Magistrate Judge Susan van Keulen, and Anthropic conceded the citation was an uncaught AI hallucination produced when Claude was asked to format the reference.
- AI tool:
- Claude.ai
What sanction did the court impose?
Judge van Keulen struck paragraph 9 of the Chen declaration and the associated footnote, finding the error a "plain and simple AI hallucination" that undermined the overall credibility of the witness's written submission. No monetary sanction was imposed, but the partial strike narrowed the evidentiary record Anthropic could rely on at the preliminary-injunction stage.
Why does Concord Music Group, Inc. v. Anthropic PBC matter for law firms using AI?
Concord v. Anthropic widens the hallucination-sanctions perimeter beyond attorney filings to expert declarations, and confirms that the rule applies even when the AI vendor is itself the party defending the case. Firms whose litigation work product relies on declarations from technical experts (forensic accountants, damages economists, data scientists) should treat AI-assisted citation formatting as a verification step their lawyers own, not one the expert can absorb. The reflexive irony of Anthropic’s own model producing the defective citation is the cautionary detail managing partners will remember.