A rape trial at Lewes Crown Court was discontinued after the complainant disclosed using an artificial intelligence (AI) chatbot to assist in preparing responses for cross-examination. The alleged victim, identified only as C in court documents, engaged with AI under various topics related to the case, including “On what happened that night,” “On Consent and Capacity,” “On Physical Evidence,” and “On Your Behaviour After,” according to disclosed conversation logs.

The defense barrister representing the accused, named R, argued that the AI's involvement compromised the fairness of the trial, as it was unclear to what extent C’s testimony had been influenced or potentially altered through these AI interactions. This raised concerns about the integrity of the evidence presented.

The Court of Appeal addressed the issue in its ruling, emphasizing that using AI in this manner effectively constitutes “witness coaching,” which is prohibited under UK law. The court stated that all witnesses should be strongly discouraged from employing AI tools to prepare their testimonies, citing the potential risks of contamination or manipulation of memory.

The judgment noted that while a truthful witness might adjust the emphasis of their account to better reflect their understanding or recollection, a dishonest witness could use AI to deliberately enhance or fabricate their testimony. UK rules allow legal professionals to prepare clients for trial but strictly forbid shaping or rehearsing evidence, a boundary seen to be violated in this case.

Initially, Lewes Crown Court concluded that the trial could not proceed fairly and called off the proceedings. However, the Court of Appeal recommended that the matter be retried, indicating that a fresh hearing would be appropriate rather than dismissing the charges altogether.

This case represents the first known instance in the UK where AI usage by a witness has directly affected courtroom proceedings, prompting legal experts and judges to consider the implications of emerging technologies on the justice system. The ruling underscores the judiciary's caution regarding AI’s potential impact on witness credibility and the administration of justice.