The National Research Council (NRC) released the third edition of its “Reference Manual on Scientific Evidence,” a guide to aid judges as they confront scientific evidence at trials. This version replaces an edition published in 2000. Developed in collaboration with the Federal Judicial Center, the manual includes new chapters on neuroscience, mental health, and forensic science. The reference work, NRC emphasizes, is meant to assist judges with the management of cases involving complex scientific and technical evidence, not to instruct them on what evidence should be admissible. Since the 1993 Supreme Court case Daubert v. Merrell Dow Pharmaceuticals, judges have had the task of determining whether expert testimony is based on sound scientific reasoning and methodology. Specifically, the manual’s new chapters “should provide an important tool for assessing evidence in several rapidly advancing fields,” says Tufts University School of Medicine’s Jerome P. Kassirer, cochair of the committee responsible for the manual’s production.