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Identifying and measuring juror bias about forensic science evidence Jury Research Symposium – Glasgow Lisa L. Smith & Prof. Ray Bull University of Leicester Forensic Psychology
Outline Measuring juror bias CSI Effect – brief look at the literature Current research When does juror bias affect decision making? Development of the Forensic Evidence Evaluation Bias (FEEB) scale Validation of the FEEB scale and mediation model
Measuring juror bias Juror demographics as predictors of verdict Age, gender, political affiliation, ethnicity, SES Personality characteristics Authoritarianism, Locus of Control, Belief in a Just World, etc. Specific scales designed to measure general attitudes toward CJS Legal Attitudes Questionnaire (LAQ), Juror Bias Scale (JBS), Pretrial Juror Attitude Questionnaire (PJAQ)
The CSI Effect Popularity of crime fiction may have an impact on jurors’ perceptions of the criminal justice system and decision making in the courtroom. CSI is not the first show to be blamed for jury behaviour in the courtroom (Mann, 2006) “Oprahization” “Perry Mason Syndrome”
Increase in student enrolment on forensic science related subjects
Police Chief’s version
Increased forensic awareness in criminals
Is there any proof that these effects exist? Pre-2006 Support for CSI Effect based only on anecdotal claims Survey of 102 attorneys in Maricopa County (Thomas, 2006) 38% reported that they had at least one trial resulting in an acquittal or hung jury because forensic evidence was not available 80% of prosecutors believe jurors are disappointed with forensic evidence presented at trials
First empirical research Podlas (2006) Investigated the existence of an anti-prosecution version of the CSI Effect N = 291 students Television viewing questionnaire followed by a mock juror task Divided participants into two groups: frequent CSI viewer (FV) and non-frequent viewer (NFV) Rape trial scenario Only issue was consent, so forensic evidence was not presented
Results of Podlas study 250 (86%) participants voted not guilty 187 of these were classified as FV of CSI Analysis revealed no significant difference between FV and NFV groups in their reasons for voting not guilty Findings did not support the existence of an anti-prosecution CSI Effect
Kim, Barak & Shelton (2009) N=1027 jurors Measured jurors’ willingness to convict without forensic evidence: Based on circumstantial evidence, OR Eyewitness testimony IVs: How often do you watch CSI? Expectations for forensic evidence Demographic variables
Kim et al., continued Results Multivariate analyses, path analysis CSI viewing had no direct effect on willingness to convict CSI viewing predicted raised expectations for forensic evidence, which in turn did influence willingness to convict Only significant in the circumstantial evidence condition
Limitations of previous research Focus on specific television programmes or genres Representation of forensic science in other media outlets is largely ignored (e.g. Movies, novels, news media, etc.) Selection of mock juror decision task Important to identify when a CSI effect bias is likely to impact juries, and use appropriate case scenarios in research
Current research Smith, Bull, & Holliday (in press) Demonstrated that mock jurors were easily able to appreciate the probative value of very strong forensic evidence When forensic evidence was of weak/moderate probative value, case context had a significant impact on the perception of evidence strength There was widespread disagreement between participants about the probative value of weak DNA evidence
The impact of case context on perceptions of the probative value of DNA evidence Smith, Bull, & Holliday (in press)
Comparison of DNA strength ratings by condition Smith, Bull, & Holliday (in press)
Rationale for the Forensic Evidence Evaluation Bias (FEEB) scale Interactionist models of jury decision making Juror bias will impact decision making when the evidence is of a weak or ambiguous standard Is it possible to identify the bias that may be operating in these cases, and use this to predict juror decisions? New approach to CSI effect research Possible use in peremptory challenges?
Development of the FEEB scale Generated 40 items based on attitudes/beliefs referred to in CSI effect literature Final version of the scale – 10 items Initial study N = 219 jury eligible members of the public Completed the FEEB scale online Principal Components Analysis (PCA) identified two distinct components (5 items loaded on to each component) Explained 47.99% of the variance
FEEB components Component 1 Component 2 If no forensics, jury should not convict No forensics means investigators didn’t look hard enough No forensics means the defendant is probably innocent Police should not charge without forensic evidence Every criminal leaves trace evidence at every scene Forensics always IDs the guilty person Forensic evidence alone is enough to convict Science is the most reliable way to ID perps Forensics always provides a conclusive answer Every crime can be solved with forensic science
Validation study N = 159 jury eligible students Completed the FEEB, Juror Bias Scale (JBS; Kassin & Wrightsman, 1983), General Belief in a Just World (GBJW; Dalbert et al., 1987) Mock juror decision making task Murder trial scenario (same as in previous studies) Weak DNA evidence, eyewitness, police, and pathologist testimony
Results PCA for the FEEB scale Same components as previous study Accounted for 58.17% of the variance Split the FEEB scale into two subscales FEEBpp – pro-prosecution items subscale (α = .82) FEEBpd – pro-defence items subscale (α = .81) Correlations between scale measures FEEBpp and JBS (r = .24, p < .05) FEEBpp and GBJW (r = .17, p < .05) FEEBpp and FEEBpd (r = -.53, p < .001)
Results continued Overall, 73 (46%) participants voted guilty Those who voted guilty estimated a higher mean probability that the defendant was guilty (80.15%) compared to those who voted not-guilty (57.19%) What predicted perceived probability of guilt? Multiple regression (DNA, eyewitness, police, pathologist evidence as predictors) Only significant predictor was DNA evidence (β = .47, p < .001)
Results continued What predicted the perceived strength of DNA evidence? Regression (predictors; FEEBpp, FEEBpd, JBS, GBJW) FEEBpp score was the only significant predictor (β = .48, p < .001)
Proposed mediation model .40* .57* .48* (.25) Note: * p < .05 Sobel test significant at p < .001
Discussion / future research Predictive ability of the FEEB scale only tested on students, and only for one crime type (e.g. murder) Next study will recruit jury-eligible members of the public and will include a rape and robbery scenario FEEBpd subscale was not a significant predictor of perceived evidence strength Include a version of scenario with no forensic evidence presented
Discussion/future research continued... Individual decision making task Future research should investigate this bias in the context of group deliberations Reducing the effect of bias Judges’ instructions? Presentation format of evidence? Practical use in peremptory challenges?
References Dalbert, C., Montada, L., & Schmitt, M. (1987). Belief in a just world: Validity correlates of two scales. PsychologischeBeitrage, 29, 596-615. Cole, S., & Dioso-Villa, R. (2007). The CSI Effect: The true effect of crime scene television on the justice system. New England Law Review, 41, 435-469. Kassin, S., & Wrightsman, L. (1986). The construction and validation of a juror bias scale. Journal of Research in Personality, 17, 423-442. Kim, Y., Barak, G., & Shelton, D. (2009). Examining the CSI effect in the cases of circumstantial evidence and eyewitness testimony: Multivariate and path analyses. Journal of Criminal Justice, 37, 452-460. Mann, M. (2006). The CSI Effect: Better jurors through television and science? Buffalo Public Interest Law Journal, XXIV. Podlas, K. (2006). The CSI Effect: Exposing the media myth. Fordham Intellectual Property, Media & Entertainment, 16, 429-465. Shelton, D., Kim, Y., & Barak, G. (2006). A study of juror expectation and demands concerning scientific evidence: Does the CSI effect exist? Vanderbilt Journal of Entertainment and Technology Law, 9, 331-368. Smith, L.L., Bull, R., & Holliday, R. (in press). Understanding juror perceptions of forensic evidence: Investigating the impact of case context on perceptions of forensic evidence strength. Journal of Forensic Sciences. Thomas, A. (2006). The CSI effect: Fact or fiction. Yale Law Journal Pocket Part, 70, 70-72.