President Donald Trump has directed federal officials to review the development and content of a scientific reference manual used by the federal judiciary, citing concerns that the publication contains political bias and discredited scientific information. The directive follows a June 19 statement posted by the president on Truth Social, in which he characterized the “Reference Manual on Scientific Evidence” as a vehicle for “political fraud.”
The manual, currently in its fourth edition, is a publication of the Federal Judicial Center (FJC), the research arm for the U.S. federal courts, produced in collaboration with the National Academies of Sciences, Engineering, and Medicine. According to the FJC, the manual serves as a guide to assist judges in managing complex scientific and technical evidence during litigation. While the guidance provided is not legally binding, it is designed to help courts assess expert evidence in accordance with scientific standards.
Concerns Over Climate Science Guidance
The focus of the presidential review centers on the fourth edition of the manual, which was released in December 2025. Specifically, the scrutiny targets a chapter titled “Reference Guide on Climate Science.” In February, the federal judiciary took the step of withdrawing this chapter from the manual following significant external pressure.
The withdrawal was prompted by a January 29 letter signed by 27 Republican state attorneys general. Led by West Virginia Attorney General JB McCuskey, the coalition argued that the chapter lacked the necessary independence and impartiality required for a judicial resource. The attorneys general contended that the manual “places the judiciary firmly on one side of some of the most hotly disputed questions in current litigation: climate-related science and ‘attribution.’” Furthermore, they alleged that the authors, Jessica Wentz and Radley Horton, consulted only with experts who aligned with a specific consensus, excluding perspectives from the U.S. Department of Energy.
Authors’ Defense and Scope of the Manual
In response to the criticism, authors Jessica Wentz and Radley Horton submitted a letter to the federal judiciary on February 25. They defended the chapter by stating that it identified the anthropogenic origin of climate change as the only “settled” scientific finding. They emphasized that the text acknowledged varying degrees of scientific uncertainty regarding the detection and projection of specific climate impacts. The authors maintained that the chapter did not take a definitive position on whether individual lawsuits or specific injuries could be directly attributed to climate change.
The fourth edition of the manual, which includes a foreword by Supreme Court Justice Elena Kagan, is intended to improve the quality of judicial decision-making by explaining scientific principles and methods. Justice Kagan noted in the foreword that the manual aids judges in assessing both the uses and potential misuses of technical evidence. Despite this, the president’s recent directive indicates that federal suspension and debarment officials will now evaluate the circumstances surrounding the chapter’s creation and its potential impact on judicial proceedings.
Next Steps in the Federal Review
The National Academy of Sciences, which cooperated on the manual’s development, has not yet provided a formal response to the president’s announcement regarding the upcoming review.
There is no immediate timeline for the conclusion of the review process. The judiciary’s next actions regarding the potential re-issuance or permanent removal of the disputed climate guidance remain pending. Further updates are expected as federal agencies begin their evaluation of the documentation and consultation processes that led to the publication of the fourth edition.
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