Identifying And Measuring Juror Bias About Forensic Science Evidence

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”

Cole & Dioso-Villa (2007)
Strong prosecutor’s effect
Jurors are acquitting in cases that lack forensic evidence
Robert Blake case is often used as an example of this effect
Weak prosecutor’s effect
Prosecutor behaviour – e.g. Explaining missing forensics, questioning jurors about viewing habits, etc.
Defendant’s effect
Jurors give forensic evidence too much weight
Jill Dando case is sometimes cited as an example

Cole & Dioso-Villa (2007) continued...
Producer’s effect
Increased awareness about forensic science
Professor’s effect
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

Comparison of DNA strength ratings by condition

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.

Identifying And Measuring Juror Bias About Forensic Science Evidence

by Michael Bromby on Apr 14, 2010

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