Probabilistic DNA evidence: The laypersons interpretation

Ritchie, J. (2015) Probabilistic DNA evidence: The laypersons interpretation. Australian Journal of Forensic Sciences, 47 4: 440-449. doi:10.1080/00450618.2014.992472

Author Ritchie, J.
Title Probabilistic DNA evidence: The laypersons interpretation
Journal name Australian Journal of Forensic Sciences   Check publisher's open access policy
ISSN 1834-562X
Publication date 2015-10-02
Year available 2015
Sub-type Article (original research)
DOI 10.1080/00450618.2014.992472
Open Access Status Not Open Access
Volume 47
Issue 4
Start page 440
End page 449
Total pages 10
Place of publication Abingdon, Oxfordshire, United Kingdom
Publisher Taylor & Francis
Collection year 2016
Language eng
Abstract A recent Australian High Court case held it was acceptable to express DNA results as either a frequency ratio or as an exclusion percentage. In order to understand if these two approaches could affect the outcome of a criminal trial, this study collected online survey data from the general public who were eligible for jury duty in Australia (n = 258). Participants were randomly assigned and completed two vignettes with two different forensic results that were manipulated in a 2×2 between-group design. Results found the way evidence was presented was sometimes statistically significant on the verdict in the case, and when not, the relationship was going in the predicted direction. Specifically when evidence was presented as an exclusion percentage, participants were more likely to convict than when presented with frequency ratio evidence. This is important as research suggests that once DNA evidence is admitted the effect can be difficult to undo, even with extensive cross-examination and testimony. DNA is a valuable tool for the criminal justice system; however, this study considers whether there is a need for standardisation in the way results are presented in a criminal trial to ensure jurors do not fallaciously reason about the evidence.
Keyword DNA evidence
jury decision-making
exemplar cueing theory
probabilistic reasoning
forensic science
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status Non-UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: Non HERDC
TC Beirne School of Law Publications
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