Tuesday 26 May 2026 11:29 am
The firm is facing backlash for AI-hallucinated letters sent to the court
A well-known London-headquartered law firm has been criticised by a High Court judge after a lawyer sent the court AI-generated letters containing false legal information. A judgment handed down on 22 May found a junior solicitor at Pinsent Masons used AI to draft two “misleading” emails containing so-called hallucinations sent to the High Court in March and April this year during an insolvency case where the firm was acting for the applicants.Pinsent Masons had written to the court in March claiming a provision in the Insolvency Rules gave power to the court to free outgoing liquidators from liability. Judge Mark Mullen said the reference to this rule “came as a surprise” to him as he “was previously unaware” of the referenced insolvency principle, despite being aware of the rules in that chapter. The judge then checked the provision against the official legislation and found it did not exist, so asked the firm to explain the reference, which sent a second letter incorrectly explaining the wording as a “summary conclusion” of a couple of rules. Judge ‘astonished’ by ‘cavalier attitude’“I was astonished by this reply. The explanation was impossible to accept,” Judge Mullen told the court. Judge Mullen added that the original letter had caused him “to be concerned that a cavalier attitude was being taken as to the accuracy of the material that Pinsent Masons were putting before the court.” “It struck me as likely to be an AI hallucination, which had not been checked. The attempt to explain it away in what appeared to be an untruthful manner in the 14th April Letter only heightened my concerns,” he said. Pinsent Masons admitted that an AI tool had been used by the junior solicitor to research the legal issue, and to later draft the second letter. “This case was a salutary reminder as to the dangers not only of over-reliance on AI, but of senior lawyers relying too heavily on junior colleagues,” Edward Levey KC, a barrister specialising in commercial and regulatory law, told City AM.Levey added that “AI is a powerful tool for lawyers when used properly.” According to the ruling, as well as fabricating legal rules the AI tool had actually warned the junior solicitor against using the material without verifying it with more reputable legal sources. ‘AI producing unreliable nonsense’Judge Mullen said it is “concerning” that the junior solicitor used AI instead of reading an official resource on the Insolvency Act’s rules, and had they done so, “it would have been readily apparent that the AI was producing nonsense and was unreliable.” Pinsent Masons has referred itself to the Solicitors Regulation Authority (SRA) which will investigate further, and the firm has apologised to the court following the incident. “We have apologised unreservedly to the Court and are taking steps to strengthen our processes and oversight to ensure this does not happen again. As the matter has been before the Court, it would not be appropriate to comment further”, Pinsent Masons said in a statement. Law firms are increasingly being caught out for relying on AI to produce unverified, hallucinated citations.Across the pond, elite US firm Sullivan & Cromwell’s in April had to apologise for multiple AI hallucinations in a bankruptcy case. In the UK, courts have had to review cases after lawyers relied on citations and quotations which turned out to be completely false.
