The judge in this patent case found that the claimants’ gene therapy expert had developed, quite possibly guided by lawyers, the understanding that the primary duty of an expert witness is not to say anything that may damage the instructing party’s case if it can be avoided.

In this US case, an expert in fiduciary services used Microsoft’s Copilot to cross-check calculations he used in expert evidence. He was unable to recall the prompts he used, state the sources Copilot relied on, or explain how the tool worked and arrived at its outputs. The judge provided some useful insight into the challenges with using AI in expert evidence.