1 Section of Forensic Genetics, Department of Forensic Medicine, Faculty of Health and Medical Sciences, Københavns Universitet2 RI ledelse, Department of Forensic Medicine, Faculty of Health and Medical Sciences, Københavns Universitet3 Comisaría General de Policía Científica, University Institute of Research in Forensic Sciences (IUICP), Madrid, Spain.4 Netherlands Forensic Institute, Department of Human Biological Traces, The Hague, The Netherlands.5 Forensic Science Institute Luis Concheiro, University of Santiago de Compostela, Spain.6 Instituto Nacional de Toxicología y Ciencias Forenses, Servicio de Biología, Barcelona, Spain.7 Cefegen, Madrid, Spain.8 Legal Medicine Institute of Valencia, Spain.9 Department of Toxicology and Health Legislation, Faculty of Medicine, Complutense University of Madrid, Spain.10 Instituto Nacional de Toxicología y Ciencias Forenses, Servicio de Biología, Sevilla, Spain.11 Laboratoire d'Hématologie Médico-Légale, Bordeaux, France.12 GHEP-ISFG, Grupo de habla española y portuguesa de la International Society for Forensic Genetics, Spain; Instituto Nacional de Toxicología y Ciencias Forenses, Servicio de Biología, Madrid, Spain.13 DNA Laboratory, Spanish Forensic Police, Granada, Spain.14 Instituto Nacional de Toxicología y Ciencias Forenses, Servicio de Biología, Madrid, Spain.15 DNA Laboratory, Spanish Forensic Police, A Coruña, Spain.16 Department of Forensic Medicine, University of Zaragoza, Spain.17 Institute of Legal Medicine, Catholic University of Sacred Heart, School of Medicine, Rome, Italy.18 Servicio de Criminalística, Dpto. de Biología, Guardia Civil, Spain.19 Unitat Central del Laboratori Biològic - Cos de Mossos d'Esquadra, Cataluña, Spain.20 Nasertic, Navarra, Spain.21 Ertzaina DNA Laboratory, Basque Country Police, Spain.22 Norwegian Institute of Public Health, Oslo, Norway; University of Oslo, Oslo, Norway. Electronic address: firstname.lastname@example.org Section of Forensic Genetics, Department of Forensic Medicine, Faculty of Health and Medical Sciences, Københavns Universitet24 RI ledelse, Department of Forensic Medicine, Faculty of Health and Medical Sciences, Københavns Universitet
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.
Forensic Science International. Genetics, 2014, Vol 9, p. 47-54