When the Supreme Court justices ruled that to determine the admissibility of scientific evidence judges must evaluate the scientific reliability (although they really meant scientific validity) of that evidence (Daubert v. Merrell Dow Pharmaceuticals, 1993), their decision prompted us to investigate a variety of psychological questions about the ability of legal decision makers to differentiate valid from junk science and the efficacy of procedural safeguards against junk science. 

Legal Decision Maker's Abilities to Evaluate Scientific Evidence

One psychological assumption underlying the Daubert decision is that judges are capable of differentiating valid science from junk science.  We surveyed judges, presenting some of them with valid research and others with research containing methodological flaws (e.g., missing control groups, confounds, experimenter bias).  Judges were equally likely to admit the valid research as the flawed research (Kovera & McAuliff, 2000).  Attorneys show a similar inability to identify flawed research (Kovera, Russano, & McAuliff, 2002). Without intervention, jurors also fail to identify confounds and experimenter bias in expert evidence (McAuliff, Kovera, & Nunez, 2008).  There is some evidence that jurors' Need for Cognition, an individual difference variable that measures an individual's willingness to engage in cognitive effort, moderates their ability to identify certain flaws.  Specifically, high Need for Cognition jurors appear to understand the problem of missing control groups better than do low Need for Cognition jurors (McAuliff & Kovera, 2008). 

Effectiveness of Procedural Safeguards against Junk Science

The Daubert decision highlighted several procedural safeguards that may prevent flawed research that is admitted at trial from influencing jurors' decisions.  Cross-examination does not seem to increase juror sensitivity to methodological flaws (Kovera, McAuliff, & Hebert, 1999).  Although opposing experts do identify flaws when they are asked to testify against an expert with flawed research (Kovera et al., 2002), opposing expert testimony about flawed methodology appears to increase juror skepticism about expert evidence rather than increasing sensitivity to methodological quality (Levett & Kovera, 2008; 2006).  Opposing experts appear to activate jurors' heuristics about experts being hired guns and that competing experts indicate a lack of consensus within the scientific community.  These heuristics mediate the skepticism effect. 

This research was funded by grants from the National Science Foundation (SES# 9711225 and 0453197).

Publications and Presentations

McAuliff, B. D., Kovera, M. B., & Nunez, G. (2008).  Can jurors recognize missing control groups, confounds, and experimenter bias in psychological science?  Law and Human Behavior.  DOI 10.1007/s10979-008-9133-0.  Retrieved at http://www.springerlink.com/content/653110767808kt43/fulltext.pdf on June 30, 2008.

Levett, L. M., & Kovera, M. B. (2008).  The effectiveness of educating jurors about unreliable expert evidence using an opposing witness.  Law and Human Behavior, 32, 363-374.

McAuliff, B. D., & Kovera, M. B. (2008). Juror Need for Cognition and sensitivity to methodological flaws in expert evidence. Journal of Applied Social Psychology, 38, 385-408.

 Levett, L. M., & Kovera, M. B.  (2006, November).  Improving the opposing expert safeguard against junk science: Does a non-adversarial expert work?  Paper presented at the meetings of the American Society of Criminology, Los Angeles, CA. 

Levett, L. M., & Kovera, M. B.  (2006, March).  Psychological mediators in the relationship between opposing expert testimony and juror decisions.  In L. M. Levett (Chair), Juror decision making about expert evidence.  Symposium presented at the meetings of the American Psychology-Law Society, St. Petersburg, FL. 

Kovera, M. B., Russano, M. B., & McAuliff, B. D. (2002). Assessment of the commonsense psychology underlying Daubert:  Legal decision makers’ abilities to evaluate expert evidence in hostile work environment cases. Psychology, Public Policy, and Law, 8, 180-200.

Russano, M. B., & Kovera, M. B. (2001, August). Psychologists’ evaluations of valid and flawed psychological science. Paper presented at the 109th Annual Convention of the American Psychological Association, San Francisco.

Kovera, M. B., & McAuliff. B. D.  (2000).  The effects of peer review and evidence quality on judge evaluations of psychological science: Are judges effective gatekeepers?  Journal of Applied Psychology, 85, 574-586. 

Kovera, M. B., McAuliff, B. D., & Hebert, K. S. (1999).  Reasoning about scientific evidence: Effects of juror gender and evidence quality on juror decisions in a hostile work environment case.  Journal of Applied Psychology, 84, 362-375.

Kovera, M. B., Levy, R. J., Borgida, E., & Penrod, S. D.  (1994).  Expert witnesses in child sexual abuse cases: Effects of expert testimony and cross-examination.  Law and Human Behavior, 18, 653-674.