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Lawyer admits ‘embarrassing’ mistake after Anthropic’s Claude made up a source in a legal filing—and no one caught it

By
Stuart Dyos
Stuart Dyos
Weekend News Fellow
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By
Stuart Dyos
Stuart Dyos
Weekend News Fellow
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May 18, 2025, 9:39 AM ET
Anthropic co-founder Jack Clark speaking at The Hill & Valley Forum
Anthropic co-founder Jack ClarkTasos Katopodis—Getty Images for 137 Ventures/Founders Fund/Jacob Helberg
  • Anthropic’s attorney admitted to using an imagined source in an ongoing legal battle between the AI company and music publishers Universal Music Group, Concord, and ABKCO Music & Records. The result of the error was that Anthropic data scientist Olivia Chen was accused of citing a made-up academic report to strengthen an argument. An associate for Athropic’s law firm took the blame, calling it an “honest citation mistake” after the inaccurate material was overlooked during a manual review.

An attorney representing Anthropic—an artificial intelligence company—admitted to incorporating an incorrect citation created by the company’s AI chatbot amid an ongoing legal battle between the company and music publishers, according to a Thursday court filing. 

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The erroneous citation was included in an expert report by Anthropic data scientist Olivia Chen last month defending claims about the company using copyrighted lyrics to train Claude, Anthropic’s large language model. Anthropic is being sued for alleged misuse of copyrighted materials to train its generative AI tools.

Although the citation carried the correct link, volume, page numbers, and publication year, the LLM, known as Claude, provided a false author and title, according to a declaration from Ivana Dukanovic, an associate at Latham & Watkins LLP and attorney of record for Anthropic. 

The acknowledgement comes after a lawyer representing Universal Music Group, Concord, and ABKCO Music & Records claimed Chen cited an imagined academic report to strengthen the company’s argument. While U.S. Magistrate Judge Susan van Keulen rejected the plaintiff’s request to question Chen, van Keulen said it was “a very serious and grave issue,” and there was “a world of a difference between a missed citation and hallucination generated by AI,” Reuters reported.

In the declaration, Anthropic attorney Dukanovictook accountability for the mishap, saying it was “an honest citation mistake and not a fabrication of authority,” according to the filing. 

She said the Latham & Watkins team found the article as “additional support for Ms. Chen’s testimony.” Then, Dukanovic asked Claude “to provide a properly formatted legal citation” for the article, which resulted in the hallucinated sourcing..

Claude did not complete the citation correctly, and the attorney’s “manual citation check did not catch that error,” according to Dukanovic. 

“This was an embarrassing and unintentional mistake,” Dukanovic said. 

Anthropic declined to provide further comment to Fortune. Latham & Watkins did not immediately respond to a request for comment.
This is the latest lawsuit challenging an AI company for allegedly misusing copyrighted materials. Media organizations like Thomson Reuters, the New York Times, and Wall Street Journal have all filed suit against various AI companies for copyright violations.

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About the Author
By Stuart DyosWeekend News Fellow

Stuart Dyos is a weekend news fellow at Fortune, covering breaking news.

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