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This legal article/report forms part of my ongoing legal commentary on the use of artificial intelligence within the justice system. It supports my work in teaching, lecturing, and writing about AI and the law and is published to promote my practice. Not legal advice. Not Direct/Public Access. All instructions via clerks at Doughty Street Chambers. This legal article concerns AI Law.

Introduction

You may have heard about “AI hallucinations” in the legal context on this blog or elsewhere. In brief, this is where an AI system creates a fake case, or a fake principle, which the parties then put before the court without checking. This is a fundamental problem with AI systems, they hallucinate, but how does that impact on professional obligations and AI Negligence?

Anyone interested in this topic should carefully read the recent judgment in Frederick Ayinde, R (on the application of) v The London Borough of Haringey [2025] EWHC 1040 (Admin), which can be found here. I’ll discuss the key points of this case below.

Summary of Case

This judicial review involved a homeless applicant seeking housing assistance from the London Borough of Haringey. After the council failed to file its defence on time and breached court directions, it was barred from further participation in the proceedings. Consequently, the court ordered the claimant be provided interim accommodation and later ruled the claimant was entitled to recover a substantial portion of his legal costs.

Separately, and crucially for our discussion, the council sought wasted costs against the claimant’s solicitors and counsel. This arose because five fictitious legal case citations had been included in the claimant’s submissions, alongside a significant misrepresentation regarding whether section 188(3) of the Housing Act 1996 imposed a mandatory or discretionary duty on councils. Mr Justice Ritchie found inserting these fictitious cases into legal pleadings was at least improper and unreasonable. The issue of negligence was slightly more nuanced (for the reasons below). Consequently, he ordered the claimant’s solicitors and counsel personally to cover a portion of the council’s costs (wasted costs), and he also reduced the claimant’s total costs award to reflect this misconduct.

Where AI Fetured

Although unproven in court, counsel for the London Borough of Haringey suggested that the fictitious authorities resulted from reliance on AI tools. The judge explicitly refrained from concluding whether AI was indeed involved, though it was undisputed that fake cases had appeared in the pleadings. Remarking on this troubling situation, the judge said:

“ It is such a professional shame. The submission was a good one. The medical evidence was strong. The ground was potentially good. Why put a fake case in?”

Highlighting the extent of the issue, the judge further noted additional fake cases, observing at one point that counsel for the claimant:

“…had moved on from fake High Court cases to fake Court of Appeal cases. I have no difficulty with the submission that the Respondent local authority had to ensure fair treatment of applicants in the homelessness review process, but I do have a substantial difficulty with members of the Bar who put fake cases in statements of facts and grounds.”

The judge then considered whether the conduct by counsel and the claimant’s solicitors had been improper, unreasonable, or negligent, concluding unequivocally that it had been “all three”.

He underscored the shared responsibility of barristers and solicitors to ensure their submissions were accurate and correct. Furthermore, he emphasised that legal professionals should report their errors transparently to their respective regulatory bodies.

Comment

The judge’s comments provide essential guidance for anyone using AI tools in legal practice. I strongly suggest all lawyers, both barristers and solicitors, read these observations carefully to understand precisely the warnings issued by the court.

Reflecting on the wasted costs application, the judge remarked:

“I think it was wholly proper for the Defendant not only to raise the matter but to ask for an explanation and then to issue a wasted costs application. This sort of behaviour should not be left unexposed. It undermines the integrity of the legal profession and the Bar.”

From my own professional experience, solicitors generally trust, and rightly so, that barristers have carefully verified the authorities they cite before submitting documents to court. Nevertheless, the judge was explicit that responsibility falls equally on both solicitors and barristers:

“I should say it is the responsibility of the legal team, including the solicitors, to see that the statement of facts and grounds are correct.”

Both barristers and solicitors must rigorously avoid misleading the court, whether knowingly or unintentionally. This case clearly demonstrates that misleading the court, particularly through citing non-existent legal cases, is considered improper, unreasonable, and negligent. The court stressed the importance of candidly self-reporting errors rather than minimising them as “minor” or merely “cosmetic”.

I’ll end with an important and timely warning applicable across all areas of legal practice involving AI-related negligence:

“…I consider that it would have been negligent for this barrister, if she used AI and did not check it, to put that text into her pleading.”

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