Science, technology, or the expert witness: What influences jurors' judgments about forensic science testimony

Jonathan J Koehler*, N. J. Schweitzer, Michael J. Saks, Dawn E. McQuiston

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

41 Scopus citations

Abstract

The impact of forensic science evidence on jurors' judgments is critically important to the criminal justice system. The assignment of low or high weight to such testimony can be the difference between acquittal or conviction. Many of the traditional forensic sciences (e.g., fingerprints and bitemarks) draw their strength largely from the subjective judgments of examiners who testify about whether evidentiary prints or other markings are consistent with (or "match") known markings from a person or object. In an online experiment (Experiment 1) and a realistic jury simulation using actual jurors or jury-eligible adults (Experiment 2), this article investigates 3 factors that might affect how jurors think about and use forensic science evidence. These factors are (a) whether the forensic science method had been scientifically tested, (b) the forensic scientist's background and experience, and (c) the sophistication of the forensic science technology. The results show a strong and consistent effect for examiner background and experience on evidence strength judgments, no effect for forensic technology sophistication, and a limited and inconsistent effect for scientific testing (present in the online experiments, absent in the realistic jury simulation). These findings raise concerns about potential undue influence of examiner background and experience on jurors' judgments and lack of clear influence of scientific testing. The implications of our findings for criminal justice practices and policies are considered.

Original languageEnglish (US)
Pages (from-to)401-413
Number of pages13
JournalPsychology, Public Policy, and Law
Volume22
Issue number4
DOIs
StatePublished - Nov 1 2016

Funding

This research was supported in part by grant 2008-DN-BX-0003 from the National Institute of Justice and the Northwestern Pritzker School of Law Faculty Research Program. We thank Craig Cooley for supplying us with transcripts of forensic science expert testimony, Alan Tuerkheimer for assisting with participant recruitment, Kayla Burd for supervising data collection, and Jessica Salerno for assisting with portions of the analyses. We also thank Charles Calleros, Joseph Feller, Art Hinshaw, Samantha Neufeld, and David DiPianto for their outstanding acting performances on the video trial.

Keywords

  • Evidence
  • Experience
  • Forensic science
  • Jury decision making
  • Testing

ASJC Scopus subject areas

  • Social Psychology
  • Sociology and Political Science
  • Law

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