Witness Coaching 2.0: From Smart Glasses to AI

The use of technology to witness coach was already in the spotlight earlier in March this year in UAB Business Enterprise & Anor v Oneta Ltd & Ors [2026] EWHC 543 (Ch), where the second claimant’s evidence was rejected in its entirety (including both his witness statement and cross-examination) after it emerged that he was receiving real-time coaching via smart glasses connected to his mobile phone during cross-examination.

Fast forward to June, and the Court of Appeal’s decision in R v F.G.D. [2026] EWCA Crim 918 marks the first appellate authority to consider AI-generated witness coaching in criminal proceedings. Although the case arose in a criminal context, the judgment has implications that extend beyond criminal proceedings and will be of interest to civil litigants and their advisors.

Background

In R v F.G.D., a witness (the complainant) admitted to using AI to "prepare myself for the court" after a download of the witness’ mobile phone uncovered two AI-generated documents containing:

• a summary of the events the witness recalled, into a clear and consistent narrative; and
• 24 pertinent questions the cross-examiner might ask with suggested answers.

The trial judge initially stayed the proceedings as an abuse of process, ruling that this constituted "witness coaching", which made a fair trial impossible. The Court of Appeal disagreed and ordered a retrial. It held that, given the evidence-in-chief was uncontaminated by AI, any prejudice caused by the witness's use of AI could have been addressed through the ordinary trial process, including disclosure of the AI-generated material to the jury and appropriate judicial directions. The court reiterated that a stay is a remedy of last resort.

Witness preparation with AI

Although in this case the Court of Appeal reversed the stay, the court's wider comments regarding the use of AI to prepare witnesses are likely to be useful and relevant to both criminal and commercial parties.

The Court of Appeal reiterated the well-established principle in R v Momodou that “witness coaching” is strictly prohibited in English criminal proceedings. This is because witnesses must give their own evidence, uninfluenced by others, to avoid the risk of influencing, tailoring or contaminating their recollection. The court warned that even an honest witness might unconsciously alter their emphasis to accommodate a "better" perception of events.

Case law suggests that witness coaching is equally impermissible in civil proceedings, where the principles in Momodou will likely also apply. E.g. Ultraframe (UK) Ltd v Fielding: “the principle that a witness’ evidence should be his honest and independent recollection, expressed in his own words, remains at the heart of civil litigation too.”

"Witness familiarisation" however, which involves explaining court layout and procedure etc., is permitted. In the present case, the two AI-generated documents crossed the line into forbidden witness coaching.

Key Takeaways

1. Discourage witnesses from AI preparation to preserve admissibility and credibility - The court expressly stated that witnesses should be "firmly discouraged" from using AI to prepare for giving evidence and warned that, in extreme cases, doing so could result in evidence being excluded altogether (as it was in UAB v Oneta). At a minimum, it provides the opposing side with significant ammunition to attack a witness's credibility during cross-examination.
2. Maintain a clear digital record if AI is used for any administrative purpose - A key aspect of the court’s reasoning for allowing the trial to proceed was that AI-generated interactions were able to be distinguished from conventional witness coaching, as they leave an auditable and discoverable record that can be scrutinised by the parties and the court.
3. Suspicion of AI use could lead to broad and intrusive disclosure orders – In this case, a full download of the witness's phone was ordered due to concerns about the adequacy of prior disclosure and the late production of evidence. The AI-generated documents were only discovered as a result of that exercise. In a commercial context, parties who suspect use of AI-assisted witness preparation may seek broader, intrusive disclosure of personal and business devices to investigate the nature and extent of any coaching.
4. The judgment aligns with the wider focus on transparency in relation to AI in civil proceedings - The judgment notes that the Civil Justice Council have recently concluded a consultation on requirements for transparency regarding AI use in civil litigation, including the preparation of witness statements. The Civil Justice Council are currently preparing a final report with recommendations.