A High Court judge publicly rebuked London-based law firm Pinsent Masons after a junior solicitor used artificial intelligence to draft two misleading letters containing fabricated legal citations during an insolvency case on May 22, 2026.
The incident occurred during a routine block transfer application to replace an administrator moving to a new firm.
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Because the application was uncontested, no opposing party was present to catch the errors.
Insolvency and Companies Court Judge Mark Mullen discovered that a letter sent on March 30, 2026, cited a nonexistent power under rule 12.37(5) of the Insolvency Rules 2016.
When asked for an explanation, the firm sent a second letter on April 14, 2026, falsely claiming the fabricated text was a summary conclusion of multiple provisions.
Internal transcripts revealed the AI tool generated plausible-sounding but inaccurate statements while explicitly warning the lawyer to verify the wording against authoritative sources.
Pinsent Masons subsequently issued an unreserved apology and referred itself to the Solicitors Regulation Authority, which is currently investigating.
Judge Details Supervision Failures
Judge Mullen detailed a severe lack of supervision regarding the junior solicitor, referred to in court documents as Lawyer A or LA.
He said the solicitor “seems to have almost entirely outsourced the thinking process to the program.”
The judge noted that he verified the official legislation online and found the cited rule contained none of the purported text, leading to a formal hearing and demands for witness statements.
“I was taken aback to be told there was such a clear rule in the IR 2016 setting out the court’s power in this regard, of which I was previously unaware,” Judge Mullen stated.
The court rejected the firm’s subsequent explanation for how the errors slipped through internal review protocols.
“I therefore checked IR 12.37(5) on the legislation. gov.
uk website and in a practitioner text to find that it says nothing of the sort,” he explained.
The oversight escalated a routine administrative matter into a broader inquiry into corporate compliance and professional standards.
“I was astonished by this reply. The explanation was impossible to accept,” Judge Mullen told the court.
He stated that the firm’s secondary correspondence aggravated the initial mistake instead of rectifying it transparently.
“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.
The court review highlighted that proper reference to physical or official digital statutes would have prevented the disruption.
Judge Mullen observed that the dialogue logs showed a striking contrast between the realistic phrasing of the technology and its factual emptiness.
“Had [the solicitor] done so, it would have been readily apparent that the AI was producing nonsense and was unreliable,” the judgment said.
The judge concluded that while the actions did not warrant contempt of court proceedings, a public reprimand and regulatory oversight were necessary.
“I have been left in no doubt that Pinsent Masons is taking this matter very seriously and is seeking to address the risks identified,” Judge Mullen said.
He noted that the interaction logs proved the technology functioned convincingly despite inserting false data into legal filings.
“What is remarkable when reading those chats is, first, that one would think that the text attributed to the AI was produced by an intelligent human being,” Judge Mullen recorded.
He further pointed out that the software routinely fabricated legal details throughout the drafting process.
“The second remarkable thing is that, on a large number of occasions, it is plainly wrong or, at the very least, extremely misleading,” he observed.
The court records indicated that the junior lawyer failed to verify any information despite explicit warnings built into the program interface.
“Assuming that LA did not check the text of the rule, I consider this omission inexcusable,” Judge Mullen stated.
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The investigation showed that supervising attorneys signed off on the correspondence without checking the statutory text themselves.
“LA seems to have almost exclusively relied upon AI to provide the answers and did not check its references, even when told to do so by the AI itself,” he said.
The judge noted that the supervising senior associate expressed deep regret during the gathering of witness statements.
“LA does not seem to have alerted their supervisors to this fact, or apparently tell them that AI had been used,” Judge Mullen noted.
He determined that the secondary letter constituted an unacceptable post-hoc rationalization of a severe legal misstatement.
“It was a construction, after the event, of a rationale for stating that the purported text was a mere summary of a number of provisions of the IR 2016 and should not be understood as a quotation,” he stated.
The judge emphasized that the firm missed a vital window to correct the record honestly before the court ordered a formal hearing.
“That was an unjustifiable response and an opportunity to set the record straight became a further instance of misleading information being put before the court,” he said.
The final judgment balanced the lack of deceptive intent against the severe breakdown of traditional legal oversight.
“There appears to have been a failure to supervise LA adequately,” Judge Mullen noted.
The court mandated that supervising staff should have scrutinized the severe errors more thoroughly before allowing the letters to be dispatched.
“Ms Poulton should have more thoroughly investigated the reasons for an egregious misstatement having been placed before the court,” he said.
He ruled out harsher judicial punishments, opting instead to validate the self-referral to the industry watchdog.
“This is plainly a case where admonishment is insufficient,” Judge Mullen concluded.
He reiterated that the behavior exhibited by the legal staff raised significant professional warning signs.
The judge concluded his assessment by highlighting the risks of ignoring direct system warnings during research.
He emphasized that a simple check of primary sources would have completely mitigated the entire controversy.
“Much of it could have been avoided had [the solicitor] simply checked any of the statutory provisions that the AI referred to in an authoritative source,” he said.
External legal experts noted that the case highlights a growing industry problem where senior professionals over-rely on unverified work from junior staff using automation.
“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 commercial and regulatory barrister, told City AM.
He maintained that automated tools still hold substantial value for the sector when paired with rigorous human verification.
“AI is a powerful tool for lawyers when used properly,” Levey added.
The firm has since restricted its commentary on the specific details of the case due to the ongoing regulatory investigation.
“We are aware of the report that Pinsent Masons have made, and we are looking into it before deciding on any potential next steps,” said an SRA spokesperson.
Pinsent Masons has implemented changes to its internal innovation and change board to prevent similar verification failures in the future.
“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.
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The Solicitors Regulation Authority will determine if further disciplinary action against the involved lawyers is required.
