What Do the Gatekeepers See? Perceptions and Evaluations of Scientific Evidence Among State Court Judges

Judicial gatekeeping decisions impact criminal case processing (e.g., verdicts, pleas) in significant ways. Despite this influential role that judges play, little is known about the key factors that contribute to judicial perceptions of evidence and the evaluative processes that judges employ in making evidentiary rulings. Using qualitative interviews with 41 state court judges presiding in a U.S. state employing the Frye standard, we explore judicial perceptions of a variety of scientific evidentiary forms and the processes by which judges reach reliability and credibility determinations in performing their gatekeeping duties. Our analyses reveal that judges are highly influenced by the general reputation of forensic evidence, often lack understanding of the scientific methodologies involved, and tend to focus on factors external to reliability (e.g., expert’s communication skills and showmanship, weight of the evidence) in their evaluative processes. Further, credibility assessments of witnesses are fraught with subjective interpretations, potentially leading to disparate evidentiary rulings.