Corresponding Author Information: Dustin Wygant

Session Abstract: Psychological testing is frequently used in forensic psychological evaluations to clarify issues of symptoms and diagnosis. The complexity of psychological tests presents a particular challenge for psychologists explaining them to the juries that often make decisions in legal cases. To date, research has not directly examined the degree to which psychological test results presented during testimony increases the persuasion of the findings or confuses the jury.  The current study utilized a series of brief videos of expert testimony in either a civil or criminal case. The criminal case included testimony about a defendant's psychological functioning at the time of the crime. The civil case included testimony about a plaintiff's symptoms of PTSD. Testimony in both cases describes the clinical symptoms of the defendant or plaintiff. The experimental condition in the project was whether the testimony included psychological test results that supports the clinical impressions of the witness.  Across each case type (criminal and civil) there were 3 conditions:

  1. Case background and clinical impressions only
  2. Case background and clinical impressions + psychological test results (MMPI-2-RF and SIRS-2 in both cases; CAPS-5 also used in civil case)
  3. Case background and clinical impressions + and additional filler material similar in content to #2 but without specific mention of psych test results

Since condition 1 is considerably shorter than condition 2, we added condition 3 to test out whether there was an effect for length of testimony. Participants were randomly selected for one of the three conditions in either the criminal or civil case (6 conditions all together). Afterwards, participants were asked a series of questions related to their understanding of the testimony and the persuasiveness of the testimony.  They also completed the Witness Credibility Scale (Brodsky et al., 2010), as well as the Science Skepticism Scale (Lewandowsky et al., 2013) and Scientific Literacy Scale (Hayes & Tariq, 2000).  Data were gathered in a sample of 393 university undergraduates (77% female) and a sample of 312 jury-eligible community members collected on Qualtrics Panels (50% female).

In the university sample, the inclusion of psychological testing was associated with lower scores on "understanding of the testimony" and higher ratings of "confusion" versus the case background only conditions. In the Qualtrics sample, participants who observed the case background + testing rated the testimony as "more persuasive" and had higher ratings on "expert appeared to have sufficient information to support his opinion" compared to the background only conditions. In each sample, lower scientific literacy and higher scores on the science skepticism measure was associated with lower ratings of understanding and persuasiveness of the testimony. Implications for including psychological testing in expert testimony will be discussed.


Dustin Wygant | Eastern Kentucky University, Richmond, KY

James Pennington | Eastern Kentucky University, Richmond, KY

Taylor Chille | Eastern Kentucky University, Richmond, KY

Jordan Organ | Eastern Kentucky University, Richmond, KY

Caycie Smith | Eastern Kentucky University, Richmond, KY

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