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GHEP-ISFG Collaborative Exercise on Mixture Profiles of Autosomal STRs (GHEP-MIX01, GHEP-MIX02 and GHEP-MIX03): Results and Evaluation

NCJ Number
Forensic Science International: Genetics Volume: 10 Dated: May 2014 Pages: 64-72
M. Crespillo; P. A. Barrio; J. A. Luque; C. Alves; M. Aler; F. Alessandrini; L. Andrade; R. M. Barretto; A. Bofarull; S. Costa; M. A. Garcia; O. Garcia; A. Gaviria; A. Gladys; A. Gorostiza; A. Hernandez; M. Herrera; L. Hombreiro; A. A. Ibarra; M. J. Jimenez; G. M. Luque; P. Madero; B. Martinez-Jarreta; M. V. Masciovecchio; N. M. Modesti; F. Moreno; S. Pagano; G. Plaza; E. Prat; J. Puente; F. Rendo; T. Ribeiro; A. Sala; E. Santamaria; V. G. Saragoni; M. R. Whittle
Date Published
May 2014
9 pages
This paper discusses the results of a collaborative exercise contrasting the methods used by different laboratories for the systematic analysis and interpretation of mixture profiles.
In order to fulfill its aim of promoting and contributing to the development and dissemination of scientific knowledge in the area of forensic genetics, the Spanish and Portuguese-Speaking Group of the International Society for Forensic Genetics (GHEP-ISFG) holds different working commissions to promote these activities. This paper discusses the results of a collaborative exercise among GHEP-ISFG member laboratories to contrast the different methods they use for systematic analysis and interpretation of mixture profiles. In all, a total of 43 laboratories, 30 belonging to public institutions and 13 affiliated with private companies, from 12 countries participated in the exercises, which were begun in 2009 and carried out in 3 editions. The results of the exercises revealed the following: in each successive edition there was an increased tendency of the laboratories toward validation of DNA mixture profile analysis following international recommendations; the majority of the discrepancies were found in stutter positions, indicating the need to perform duplicate analysis using different kits in order to reduce errors; and when laboratories were allowed to develop their own hypotheses to calculate the likelihood ratio (LR) value, several options were proposed leading to significant differences in the final LR values obtained during the exercises. This last finding has significant implications for criminal cases. 6 tables, 1 appendix, and 25 references