Criminal Adjudication: The Challenges of Forensic Science Evidence in the Early 21st Century

Abstract

This study examines the status of forensic science in criminal cases. After reviewing the history of the use of criminal forensic science testimony, the Daubert trilogy of Supreme Court cases establishing new tests for admissibility of scientific evidence and making trial judges the "gatekeeper" for such evidence is reviewed. New pretrial issues posed by forensic science are discussed.

The study systematically reviews admissibility issues regarding various types of common forensic evidence, including social science evidence, DNA, fingerprints, handwriting comparison, hair analysis, bitemark analysis, toolmark, firearm and bullet lead comparison, fire, explosion and arson evidence, and bloodstain pattern evidence. Each area is examined for its scientific basis and questions about its admissibility under Daubert, especially in light of the recent National Research Council Report questioning the validity of much non-DNA science in criminal cases and for the reactions of judges to their Daubert gatekeeping responsibilities in each area.

The reactions of jurors to forensic evidence are examined and specifically the studies of juror expectations and demands for scientific evidence are reviewed. The increasing demand of jurors for stronger evidence of guilt is related directly to cultural changes resulting in increased awareness of the power of modern technology in the criminal justice system, especially regarding the use of DNA. The reactions of attorneys and judges to this phenomenon are discussed.

Several factors have created significant doubts about whether such evidence should be used, including Daubert, the emergence of DNA as a model for scientific evidence, the use of DNA to exonerate persons who were convicted using other forms of supposedly scientific evidence, the findings of the NRC Report, and new technology awareness by jurors. The study concludes that scientists, scholars and the NRC Report have shown most non-DNA forensic evidence to be of insufficient validity to be used in criminal proceedings. Nevertheless most judges have refused to exclude such evidence and have abdicated their gatekeeping role and continued routine admission of prosecution expert testimony.

Research by the scientific and academic communities may lead to improved scientific information but many practitioners may oppose any reform efforts. Legislation based on the NRC report may not materialize in the face of prosecution opposition. The study suggests that the dogged resistance of judges to exclude government expert testimony is likely the result of systemic judicial pro-prosecution bias and that reform emanating from trial or appellate judges is unlikely. It is suggested perhaps the best prospect for reform is tech-savvy jurors who, when presented with evidence of the questionable validity of non-DNA science, may well refuse to convict and that such acquittals may be the only way to convince prosecutors to stop using such unreliable evidence.

University of Nevada Reno Ph.D. Dissertation.

Keywords: evidence, forensic science, criminal law, courts