In re Valsartan MDL (Dr. William Sawyer)

What happened

The Valsartan multidistrict litigation concerns claims that contaminated blood-pressure medication caused cancer. In the bellwether case brought by Gaston Roberts, the plaintiff offered Dr. William Sawyer as an expert on toxicology. Defendants moved to exclude his testimony, and Chief Judge Renée Marie Bumb referred the motion to the Special Master, retired 3rd Circuit Judge Thomas I. Vanaskie.

Part of the challenge concerned the report's citations. The Special Master's order refers to "Dr. Sawyer's citation to non-existent sources due to his use of an artificial intelligence tool without adequate verification of the sources generated by the artificial intelligence tool." Commentary on the briefing reports that 10 citations were affected and that Dr. Sawyer said he had used "either Google or AI." The tool is not identified in the sources reviewed.

What the court did

On September 3, 2025, the Special Master denied the motion to exclude (Dkt. 3167). The order states that the citation problem, "while perhaps warranting an award of costs in favor the defense and permitting cross examination of Dr. Sawyer during the trial on his failure to verify the sources cited in his report, does not warrant exclusion of his opinions." The order found the opinions otherwise the product of reliable scientific methodology. It did not itself award costs.

The same day, Chief Judge Bumb excluded the testimony of another of the plaintiff's experts, Dr. Siddiqui, on causation. The plaintiff conceded that summary judgment was then appropriate on all claims. The opinion noted the Special Master's ruling on Dr. Sawyer and stated: "In light of the instant Opinion, any appeal would be moot."

Where it stands

The Sawyer ruling was not reviewed by the district judge because the bellwether case ended on summary judgment for reasons unrelated to AI. Whether the issue will be raised again in other cases in the MDL is not established by the record reviewed.

The obligation it engaged

The conduct engaged Clause 3, independent authority. Sources generated by a system entered the report without being confirmed against the sources themselves, and some did not exist. The order's own phrase, use "without adequate verification," describes exactly the step Clause 3 requires.

The Special Master separated the citations from the methodology and found the methodology reliable. That is the same separation the Standard's governing test draws: whether a competent examiner working from the primary sources could reproduce the result. The defect remained a matter for cross-examination and possible costs. An expert who confirms each citation before signing, and records that step under Clause 7, avoids giving opposing counsel that line of questioning.

Clause 4, checkability before adoption, is also engaged. A citation list is the most checkable part of a toxicology report, and each entry could have been confirmed in a library or database before the report was served.

Sources

• U.S. District Court, D.N.J. (via CourtListener RECAP) · September 3, 2025
  Special Master Order, Dkt. 3167
• U.S. District Court, D.N.J. (via CourtListener) · September 3, 2025
  Gaston Roberts, et al. v. Zhejiang Huahai Pharmaceutical Co., Ltd., et al., Opinion
• Reason (The Volokh Conspiracy) · December 7, 2025
  Expert Report Admitted Despite AI Hallucinations in Citations

What could not be confirmed

The count of 10 citations and the statement about "either Google or AI" come from commentary on the briefing, not from the order. A report that Dr. Sawyer initially testified he had reviewed the sources was not confirmed.