Different likelihood ratio approaches to evaluate the strength of evidence of MDMA tablet comparisons

Details

Serval ID
serval:BIB_D3D603F5FCCE
Type
Article: article from journal or magazin.
Collection
Publications
Institution
Title
Different likelihood ratio approaches to evaluate the strength of evidence of MDMA tablet comparisons
Journal
Forensic Science International
Author(s)
Bolck A., Weyermann C., Dujourdy L., Esseiva P., Van den Berg J.
ISSN
0379-0738
Publication state
Published
Issued date
10/2009
Peer-reviewed
Oui
Volume
191
Number
1-3
Pages
42-51
Language
english
Abstract
Two likelihood ratio (LR) approaches are presented to evaluate the strength of evidence of MDMA tablet comparisons. The first one is based on a more 'traditional' comparison of MDMA tablets by using distance measures (e.g., Pearson correlation distance or a Euclidean distance). In this approach, LRs are calculated using the distribution of distances between tablets of the same-batch and that of different-batches. The second approach is based on methods used in some other fields of forensic comparison. Here LRs are calculated based on the distribution of values of MDMA tablet characteristics within a specific batch and from all batches. The data used in this paper must be seen as examples to illustrate both methods. In future research the methods can be applied to other and more complex data. In this paper, the methods and their results are discussed, considering their performance in evidence evaluation and several practical aspects. With respect to evidence in favor of the correct hypothesis, the second method proved to be better than the first one. It is shown that the LRs in same-batch comparisons are generally higher compared to the first method and the LRs in different-batch comparisons are generally lower. On the other hand, for operational purposes (where quick information is needed), the first method may be preferred, because it is less time consuming. With this method a model has to be estimated only once in a while, which means that only a few measurements have to be done, while with the second method more measurements are needed because each time a new model has to be estimated.
Keywords
Drug profiling , MDMA , Multivariate distributions , Pearson , Evidence evaluation , Likelihood ratio
Create date
09/10/2009 7:35
Last modification date
20/08/2019 16:53
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