How to assign a likelihood ratio in a footwear mark case: an analysis and discussion in the light of R v T

Details

Serval ID
serval:BIB_994BA83CC48B
Type
Article: article from journal or magazin.
Collection
Publications
Institution
Title
How to assign a likelihood ratio in a footwear mark case: an analysis and discussion in the light of R v T
Journal
Law, Probability and Risk
Author(s)
Biedermann A., Taroni F., Champod C.
ISSN
1470-840X
ISSN-L
1470-8396
Publication state
Published
Issued date
12/2012
Volume
11
Number
4
Pages
259-277
Language
english
Abstract
This article analyses and discusses issues that pertain to the choice of relevant databases for assigning values to the components of evaluative likelihood ratio procedures at source level. Although several formal likelihood ratio developments currently exist, both case practitioners and recipients of expert information (such as judiciary) may be reluctant to consider them as a framework for evaluating scientific evidence in context. The recent ruling R v T and ensuing discussions in many forums provide illustrative examples for this. In particular, it is often felt that likelihood ratio-based reasoning amounts to an application that requires extensive quantitative information along with means for dealing with technicalities related to the algebraic formulation of these approaches. With regard to this objection, this article proposes two distinct discussions. In a first part, it is argued that, from a methodological point of view, there are additional levels of qualitative evaluation that are worth considering prior to focusing on particular numerical probability assignments. Analyses will be proposed that intend to show that, under certain assumptions, relative numerical values, as opposed to absolute values, may be sufficient to characterize a likelihood ratio for practical and pragmatic purposes. The feasibility of such qualitative considerations points out that the availability of hard numerical data is not a necessary requirement for implementing a likelihood ratio approach in practice. It is further argued that, even if numerical evaluations can be made, qualitative considerations may be valuable because they can further the understanding of the logical underpinnings of an assessment. In a second part, the article will draw a parallel to R v T by concentrating on a practical footwear mark case received at the authors' institute. This case will serve the purpose of exemplifying the possible usage of data from various sources in casework and help to discuss the difficulty associated with reconciling the depth of theoretical likelihood ratio developments and limitations in the degree to which these developments can actually be applied in practice.
Create date
10/12/2012 8:21
Last modification date
20/08/2019 15:00
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