In Daubert v. Merrell Dow Pharmaceuticals, decided on June 28, 1993, the Supreme Court made trial judges gatekeepers for expert testimony. “The trial judge must ensure that any and all scientific testimony or evidence admitted is not only relevant, but reliable.” A key question is whether a theory “can be (and has been) tested.”
Admitted evidence still faces attack. The Court named “vigorous cross-examination, presentation of contrary evidence, and careful instruction on the burden of proof” as “the traditional and appropriate means of attacking shaky but admissible evidence.”