Anthropic's Claude Generates Fake Citation in Copyright Lawsuit
Anthropic admitted in a copyright lawsuit that its AI chatbot Claude fabricated a source citation, including an inaccurate article title and false author names, which appeared in expert witness testimony. The company acknowledged the error as an "honest citation mistake" and formally apologized to the court.
What happened
Anthropic's attorneys asked Claude to generate a legal citation for an academic article titled 'Binomial Confidence Intervals for Rare Events: Importance of Defining Margin of Error Relative to Magnitude of Proportion' by Owen McGrath and Kevin Burke. Although Claude correctly identified the publication title, year, and link, it generated an inaccurate article title and invented false author names.
The fabricated citation appeared in a declaration by Anthropic employee Olivia Chen, who served as an expert witness in a copyright lawsuit brought by music publishers including Universal Music Group. The error passed through manual review and was later discovered by opposing counsel during court proceedings, prompting Judge Susan van Keulen to demand an explanation from Anthropic.
Reported impact
Music publishers accused Anthropic's expert witness of violating court rules by using Claude to develop arguments and citations in her declaration. Anthropic acknowledged the citation error, describing it as an 'honest citation mistake and not a fabrication of authority,' though the underlying article does exist and supports Chen's statement.
Index analysis
Claude's error involved hallucinating author names and an article title while retaining correct metadata about the publication, year, and URL. Anthropic stated that additional citation and wording mistakes from Claude also appeared in the footnotes during the formatting process, though the company did not release a complete list of faulty citations.
Governance controls
Anthropic's manual review process failed to detect the fabricated citation and other errors before the declaration was filed with the court. Anthropic's attorney was required to formally apologize to the court for the errors.
Classification
Sources and evidence
This record was researched and written by the Index, based on the following original reporting.