Using AI to Prepare to Give Evidence: Why the Court of Appeal says think twice

By Bob Denaro (KPM) · BDG Training Team · August 2026

Using AI to prepare to give evidence can amount to witness coaching — that is the clear warning from the Court of Appeal in R v FGD [2026] EWCA Crim 918. A prosecution witness had used AI to generate a mock cross-examination of their account, complete with suggested answers. This post explains what happened, what the court decided, and what it means for anyone who gives evidence.

What happened in R v FGD?

During a rape trial at Lewes Crown Court, the prosecution witness used AI to produce questions in the form of a cross-examination of their account, together with suggested answers. The defence applied to stay the proceedings, arguing that a fair trial was impossible because no amount of cross-examination could separate the witness's own evidence from what the tool had supplied. The trial judge agreed it amounted to coaching and stayed the case as an abuse of process.

What did the Court of Appeal decide?

The Court of Appeal (Lady Justice May, Mr Justice Griffiths and HHJ Picton) overturned the stay, holding that the prejudice could be managed by other safeguards. But it took the opportunity to warn all witnesses against resorting to AI to prepare for giving evidence.

What is the difference between coaching and familiarisation?

Lady Justice May cited Judge LJ in R v Momodou and Limani [2005] EWCA Crim 177 at [61]: there is a dramatic distinction between witness training or coaching and witness familiarisation. Familiarisation which is understanding the court layout and the general experience of giving evidence, is permitted. Training or coaching a witness in their evidence, whether for prosecution or defence, is not.

Why does using AI count as coaching?

The court accepted that AI is now used for everyday tasks, including research and interview preparation. But coaching a witness in their evidence, by any means, is not permitted. Generating suggested answers risks the evidence no longer being genuinely the witness's own, the very mischief the coaching rule guards against.

What is the risk if a witness uses AI?

In an extreme case, resorting to AI could create such unfairness that the court has to consider excluding the evidence altogether. The principle is likely to reach civil proceedings too, particularly given the Civil Justice Council's ongoing consultation on the use of AI in preparing court documents.

Frequently asked questions

Can a witness use AI to prepare for cross-examination?

They should be firmly discouraged from doing so. In R v FGD the Court of Appeal warned that using AI to prepare to give evidence can amount to prohibited witness coaching.

Is witness familiarisation still allowed?

Yes. Familiarisation with the court process and the experience of giving evidence is permitted; coaching a witness on the content of their evidence is not.

Does this apply only to criminal cases?

R v FGD is a criminal case, but the principle is likely to apply in civil proceedings as well.

BDG's Giving Evidence and Professional Witness Skills training prepares investigators to give evidence with confidence, through proper familiarisation and briefing, not shortcuts.

Contact info@bdgtrainingconsultancy.co.uk to arrange a course.