In its famous opinion in Daubert v. Merrell Dow Pharmaceuticals, the U.S. Supreme Court took a major step toward assuring that our legal system functions on the basis of sound scientific principles. The Court held that judges must apply criteria based on such principles when they decide whether to admit expert testimony. Daubert was a reaction to the well-documented problem of court decisions that are based on “junk science”—opinions offered in evidence by supposed experts but that are not supported by reliable data and analysis. Daubert requires an expert witness to disclose the data and methodology they relied on as the basis for any opinion they propose to offer in court. The judge then decides whether the data and methodology are suffi...