An expert witness hired by 3M used ChatGPT to write significant portions of an expert report in litigation over the 2020 explosion at Watson Grinding, a Houston manufacturing facility. The explosion killed three people and destroyed roughly 200 homes. Court transcripts, deposition documents, and discovery records indicate that the witness’s ChatGPT prompts were disclosed publicly. One prompt asked the system to create “an exceptional expert witness report defending the standard of care at 3M” and to “show how 3M is 0% at fault for the explosion at Watson Grinding.” The U.S. Chemical Safety and Hazard Investigation Board said the explosion resulted from a degraded and poorly crimped rubber welding hose that leaked flammable gas, which later ignited. Dozens of homeowners have sued 3M and Watson Grinding, with plaintiffs alleging that 3M failed to properly service the facility’s gas-detection system and committed other errors contributing to the blast. The ongoing case involves potential total liability in the hundreds of millions of dollars. The disclosed records show that AI use in court proceedings can extend to expert-witness reports and that the underlying prompts may be discoverable by opposing parties.