Expert psychological testimony, like any testimony, must meet certain criteria or standards for admissibility before it is allowed into court. Although the admissibility of expert evidence was initially governed by the general acceptance standard set in Frye v. United States(1923), more recent standards, including the Federal Rules of Evidence, have shifted focus to an evaluation of the reliability of the evidence. This entry outlines the historical changes in admissibility standards, starting with the Frye decision and the Federal Rules of Evidence and progressing through a trio of recent Supreme Court decisions that address the admissibility of expert evidence. These decisions include Daubert v. Merrell Dow Pharmaceuticals (1993), which established whether the Federal Rules of Evidence superseded the Frye standard when judging the admissibility of scientific ...