A rape trial that was previously halted due to the complainant’s use of artificial intelligence (AI) to prepare for cross-examination will now proceed, following a decision by the Court of Appeal, Criminal Division. The court ruled that the trial should not have been stopped simply because the complainant had used AI to anticipate questions and generate suggested answers before the hearing.

The case involved a defendant, anonymised as FGD, charged with rape at the Crown Court in Lewes. The complainant, known only as C, had a prior casual sexual relationship with the defendant but had ended the relationship several weeks before the alleged incident. On the night in question, according to the prosecution, C was intoxicated on alcohol and drugs and incapable of consenting to sex, a condition the defendant was alleged to have known. The defence denied that any penetration occurred and alternatively argued that any sexual activity was consensual.

C was the sole prosecution witness. During cross-examination, the defence requested a full download of C’s phone, which revealed documents summarising the complainant’s recollections of the night, along with a series of potential cross-examination questions and suggested responses. These documents appeared to be produced with the assistance of AI, serving as a form of witness coaching—an action prohibited in legal proceedings. When asked, C admitted to having used AI to help prepare for court.

Following this discovery, the trial judge, Mr Recorder Hay, ruled that the proceedings should be stayed on the grounds that a fair trial was no longer possible, concluding that the use of AI constituted an abuse of process. However, the Court of Appeal found this decision to be an error. Lady Justice May, delivering the judgment, noted that C’s evidence-in-chief had been recorded in a pre-trial police interview conducted years earlier, before any use of AI, and was therefore uncontaminated. The court emphasised that only the answers given during cross-examination were potentially influenced by the AI-generated materials.

The appellate court held that the impact of AI-assisted preparation could be appropriately addressed by informing the jury about the nature of the AI documents and providing judicial directions on their evidentiary weight. Unlike traditional witness coaching, which often takes place privately and unrecorded, the AI-generated guidance was fully documented and could be made available in court, ensuring transparency. The Court of Appeal therefore allowed the Crown’s appeal, setting aside the stay of proceedings and ordering a retrial.

The judgment also highlighted broader legal and procedural concerns surrounding the increasing use of AI in legal contexts. While AI is becoming a common tool for research and preparation across various fields, its use in coaching witnesses is not permitted due to risks of unfairness. The court warned that the use of AI by complainants in sexual offence cases might lead to wider disclosure and intrusive investigation of their digital records and personal data, potentially exposing information to unintended public access.

The Court of Appeal raised concerns about the wide-ranging scope of phone downloads ordered in such cases, stressing the need for reasonable and proportionate searches under established legal standards. The ruling suggested that police, prosecutors, and legal rulemaking bodies consider formal guidelines to address the implications of AI’s role in criminal justice proceedings, noting that this case was likely not the last to raise such issues.