Crown Prosecution Service submitted AI-hallucinated case citations to the High Court

Crown Prosecution Service (UK)·generative AI legal research tool (unnamed)

CPS lawyers used generative AI for legal research on an extradition appeal to Romania; two completely fictitious legal authorities that were 'likely generated through the use of generative AI' were included in the CPS's grounds of opposition and then repeated in further submissions by junior counsel before the High Court.

Blast radius

Two fabricated case citations were part of formal court filings in more than one submission before the High Court; the CPS reviewed almost 80 other cases handled by the same lawyer, finding no other issues, and there was no impact on the case outcome because the errors were caught before the hearing.

Root cause

The hallucinated citations were not verified before formal filing and were copied uncritically from one document into another across multiple stages of review.

How it was caught

Not identified during the court's permission stage; only surfaced when questions were raised shortly before the hearing.

What changed

The CPS apologised to the court, carried out an internal review, and said it had reinforced its verification processes.

Take-awayEvery AI-assisted legal citation needs to be checked against a primary legal database before filing, no matter how many prior reviewers have already seen it.