Fake authorities cited by counsel in the High Court—AI suspected

Ayinde v The London Borough of Haringey [2025] EWHC 1040 (Admin) is partly a decision about relief from sanctions in the context of a judicial review in a housing matter. A link to the case is here. The underlying facts are tragic. The claimant was forced to leave his home and was made homeless. He had severe medical needs, including chronic kidney disease, which culminated in him suffering a heart attack. The Defendant borough did not deem him a priority to house and so he was forced to sleep on park benches and on sofas. He became suicidal. The judicial review was ultimately disposed of by agreement and the claimant was therefore likely granted priority housing status.

But Ayinde is also a case about wasted costs—where a legal representative is ordered to pay some of a party’s own costs. It will be particularly interesting to practitioners because the claimant’s barrister relied on fake cases in her submissions and the claimant’s solicitors failed to do anything about it. The suggestion from the defendant was that they were generated by AI, echoing Felicity Harber v The Commissioners for HMRC [2023] UKFTT 1007 (TC) and the US case of Mata v Avianca.

The claimant’s statement of facts and grounds referred to five authorities in support of various legal propositions. The defendant wrote to the claimant’s solicitors saying that, having read the statement of facts and grounds, they could not find some of the cases the claimant referred to. The claimant’s solicitors ignored this. The defendant wrote again asking for copies of the cases. No real explanation was given before the hearing. The claimant’s solicitors referred to them in correspondence as “erroneous citation in the grounds, which are easily explained”.

However, at the hearing, the only explanation given by the claimant’s barrister was that she “kept a box of copies of cases and she kept a paper and digital list of cases with their ratios in it. She dragged and dropped the case” into her submissions. Unsurprisingly, Ritchie J rejected this explanation. He found that the cases were fake and that the behaviour of the claimant’s solicitors and barrister was improper, unreasonable and negligent. He went on to say:

“It is wholly improper to put fake cases in a pleading. It was unreasonable, when it was pointed out, to say that these fake cases were "minor citation errors" or to use the phrase of the solicitors, "Cosmetic errors". 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. They should have been shocked when they were told that the citations did not exist. [The claimant’s barrister] should have reported herself to the Bar Council. I think also that the solicitors should have reported themselves to the Solicitors Regulation Authority. I consider that providing a fake description of five fake cases, including a Court of Appeal case, qualifies quite clearly as professional misconduct.”

The defendant’s barrister suggested that AI was the culprit. It’s important to say that Ritchie J did not make a finding that the claimant’s barrister did use AI but the descriptions of the cases read exactly like AI hallucinations—and the claimant’s barrister was unable to give any other sensible explanation.

Ritchie J had the following salutary warning:

“On the balance of probabilities, 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. However, I am not in a position to determine whether she did use AI. I find as a fact that [the claimant’s barrister] intentionally put these cases into her statement of facts and grounds, not caring whether they existed or not, because she had got them from a source which I do not know but certainly was not photocopying cases, putting them in a box and tabulating them, and certainly not from any law report. I do not accept that it is possible to photocopy a non-existent case and tabulate it. Improper and unreasonable conduct are finding about which I am sure. In relation to negligence I am unsure but I consider that it would fall into that category if [the claimant’s barrister] obtained the text from AI and failed to check it.”

Both the claimant’s solicitors and barrister were ordered to pay wasted costs and the judge ordered the transcript of the judgment to be sent to the Bar Standards Board and to the Solicitors Regulation Authority.