On the interpretation of likelihood ratios in forensic science evidence: Presentation formats and the weak evidence effect

Abstract Likelihood ratios are increasingly being adopted to convey expert evaluative opinions to courts. In the absence of appropriate databases, many of these likelihood ratios will include verbal rather than numerical estimates of the support offered by the analysis. However evidence suggests tha...

Full description

Saved in:
Bibliographic Details
Published in:Forensic science international 2014-07, Vol.240, p.61-68
Main Authors: Martire, K.A, Kemp, R.I, Sayle, M, Newell, B.R
Format: Article
Language:English
Subjects:
Adolescent
Adult
Aged
Communicating uncertainty
Criminal Law
Equivalence
Evidence interpretation
Expert evaluative opinions
Female
Forensic science
Forensic sciences
Forensic Sciences - legislation & jurisprudence
Humans
Hypotheses
Likelihood Functions
Likelihood ratio
Likelihood ratios
Male
Mathematical models
Middle Aged
Pathology
Probability
Prosecutions
Ratios
Strength
Students
Studies
Tables (data)
Visual
Young Adult
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:Abstract Likelihood ratios are increasingly being adopted to convey expert evaluative opinions to courts. In the absence of appropriate databases, many of these likelihood ratios will include verbal rather than numerical estimates of the support offered by the analysis. However evidence suggests that verbal formulations of uncertainty are a less effective form of communication than equivalent numerical formulations. Moreover, when evidence strength is low a misinterpretation of the valence of the evidence – a “weak evidence effect” – has been found. We report the results of an experiment involving N = 404 (student and online) participants who read a brief summary of a burglary trial containing expert testimony. The expert evidence was varied across conditions in terms of evidence strength (low or high) and presentation method (numerical, verbal, table or visual scale). Results suggest that of these presentation methods, numerical expressions produce belief-change and implicit likelihood ratios which were most commensurate with those intended by the expert and most resistant to the weak evidence effect. These findings raise questions about the extent to which low strength verbal evaluative opinions can be effectively communicated to decision makers at trial.
ISSN:0379-0738
1872-6283
DOI:10.1016/j.forsciint.2014.04.005