Law360, London (July 10, 2026, 9:35 PM BST) -- Prosecutors included fake cases that did not exist in an extradition appeal after the artificial intelligence program they used hallucinated citations, according to a High Court judgment.

The Crown Prosecution Service cited two made-up cases produced by an unnamed generative AI system as part of extradition proceedings at the High Court, Judge Derek Sweeting said.

Counsel failed to check the cases after the fact, and they were submitted as part of the CPS' written arguments though not relied upon at the hearing, Judge Sweeting wrote in the judgment handed down July 8.

The fake cases therefore did not impact the court's decision, the judge said, and were only spotted when opposing counsel failed to find the authorities in any legal directory.

"It would be naive to assume that there will not be an increasing use of artificial intelligence in legal work in [the] future; indeed, that may be both necessary and beneficial," Judge Sweeting said. "The episode highlights the risks of its use without appropriate oversight particularly for legal research."

CPS apologized, blamed "human error" and said it reviewed 78 cases involving the same lawyer. None of those identified similar issues, "and the lawyer's work was otherwise assessed to be of a good standard," the judge noted.

The error was "not a deliberate attempt to mislead, but rather an isolated incident arising from inadequate checking of written work," according to the judgment.

The cases were first introduced by the CPS in written arguments opposing a challenge to an extradition ordered last year.

The cases were then repeated in the CPS' submissions prepared by junior counsel. The fake citations continued through to the full hearing, though they were not relied upon.

Widespread adoption of AI by law firms, regulators and prosecutors has promised tremendous time savings particularly for resource-strapped agencies operating under intense time pressures. 

Judges have reprimanded lawyers for using AI to draft documents littered with errors in the Upper Tribunal, while Pinsent Masons LLP has referred itself to the Solicitors Regulation Authority after admitting that one of its junior lawyers used artificial intelligence to generate made-up law in letters sent to court. 

On the bench, Justice Colin Birss said in May that AI has improved his judgments, though he cautioned against having it write rulings from scratch.

In June 2025, a Kuwaiti businessman lost his £89.4 million ($122.8 million) claim against a Qatari bank in a case littered with "hallucinatory" references to cases that didn't exist.

The case is Andreea-Maria Tobosaru v. Court of Law Craiova, Romania, case number AC-2025-LON-001318, in the High Court of Justice of England and Wales.

--Additional reporting by Sophia Duorou and Eddie Beaver. Editing by Janice Carter Brown.

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