From Magistrate Judge Stephanie Christensen (C.D. Cal.) in Creditors Adjustment Bureau, Inc. v. All Season Power LLC, decided Feb. 13 but just posted on Westlaw:

Both parties cited a non-existent case in their briefs.

Specifically, after Plaintiff's opposition and Defendant's reply were filed, Plaintiff's counsel filed a declaration providing that "certain quoted material set forth in Plaintiff's brief … [wa]s not accurate, and in one instance, from a non-existent case." The declaration identified four false citations comprising one non-existent case and three non-existent quotes from real cases. Plaintiff's counsel further declared that "[i]t appears that some legal research that was done on this case relied upon artificial intelligence and resulted in these phantom quotes and citations."

Defendant's counsel subsequently filed a declaration providing that "one of the same erroneously cited cases was also referenced [in Defendant's reply.]" Counsel for Defendant further declared that "[t]his error was inadvertent and was not related to any AI usage by Defendant's counsel." In other words, they merely followed Plaintiff's counsel over the cliff.

The Court certainly does not insist on candlelight in this age of electricity. Using compute power to find the holding in the haystack is essential. But counsel would do well to remember that "[a]t the very least, the duties imposed by Rule 11 require that attorneys read, and thereby confirm the existence and validity of, the legal authorities on which they rely."

Perhaps due to the asynchronous Thelma and Louise, neither side requests sanctions. Still, the parties are warned that further reliance on synthetic citations will warrant them….