Abstract
There has been very little work published on the variation of reporting practices
of mixtures between laboratories, but it has been previously demonstrated that there
is little consistency. This is because there is no current uniformity of practice,
so different laboratories will operate using different rules. The interpretation of
mixtures is not solely a matter of using some software to provide ‘an answer’. An
assessment of a case will usually begin with a consideration of the circumstances
of a crime. Assumptions made about the numbers of contributors follow from an examination
of the electropherogram(s) – and these may differ between the prosecution and the
defence hypotheses. There may be a necessity to evaluate several sets of hypotheses
for any given case if the circumstances are uncertain. Once the hypotheses are formulated,
the mathematical analysis is complex and can only be accomplished by the use of specialist
software. In order to obtain meaningful results, it is essential that scientists are
trained, not only in the use of the software, but also in the methodology to understand
the likelihood ratio concept that is used. The Euroforgen-NoE initiative has developed
a training course that utilizes the LRmix program to carry out the calculations. This
software encompasses the recommendations of the ISFG DNA commissions on mixture interpretation
and is able to interpret samples that may come from two or more contributors and may
also be partial profiles. Recently, eighteen different laboratories were trained in
the methodology. Afterwards they were asked to independently analyze two different
cases with partial mixture DNA evidence and to write a statement court-report. We
show that by introducing a structured training programme, it is possible to demonstrate,
for the first time, that a high degree of standardization, leading to uniformity of
results can be achieved by participating laboratories.
Keywords
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Article info
Publication history
Accepted:
October 22,
2013
Received in revised form:
October 14,
2013
Received:
July 6,
2013
Identification
Copyright
© 2013 Elsevier Ireland Ltd. Published by Elsevier Inc. All rights reserved.
