title: GHEP-ISFG collaborative exercise on mixture profiles of autosomal STRs (GHEP-MIX01, GHEP-MIX02 and GHEP-MIX03): results and evaluation.
abstract: One of the main objectives of the Spanish and Portuguese-Speaking Group of the International Society for Forensic Genetics (GHEP-ISFG) is to promote and contribute to the development and dissemination of scientific knowledge in the area of forensic genetics. Due to this fact, GHEP-ISFG holds different working commissions that are set up to develop activities in scientific aspects of general interest. One of them, the Mixture Commission of GHEP-ISFG, has organized annually, since 2009, a collaborative exercise on analysis and interpretation of autosomal short tandem repeat (STR) mixture profiles. Until now, three exercises have been organized (GHEP-MIX01, GHEP-MIX02 and GHEP-MIX03), with 32, 24 and 17 participant laboratories respectively. The exercise aims to give a general vision by addressing, through the proposal of mock cases, aspects related to the edition of mixture profiles and the statistical treatment. The main conclusions obtained from these exercises may be summarized as follows. Firstly, the data show an increased tendency of the laboratories toward validation of DNA mixture profiles analysis following international recommendations (ISO/IEC 17025:2005). Secondly, the majority of discrepancies are mainly encountered in stutters positions (53.4%, 96.0% and 74.9%, respectively for the three editions). On the other hand, the results submitted reveal the importance of performing duplicate analysis by using different kits in order to reduce errors as much as possible. Regarding the statistical aspect (GHEP-MIX02 and 03), all participants employed the likelihood ratio (LR) parameter to evaluate the statistical compatibility and the formulas employed were quite similar. When the hypotheses to evaluate the LR value were locked by the coordinators (GHEP-MIX02) the results revealed a minor number of discrepancies that were mainly due to clerical reasons. However, the GHEP-MIX03 exercise allowed the participants to freely come up with their own hypotheses to calculate the LR value. In this situation the laboratories reported several options to explain the mock cases proposed and therefore significant differences between the final LR values were obtained. Complete information concerning the background of the criminal case is a critical aspect in order to select the adequate hypotheses to calculate the LR value. Although this should be a task for the judicial court to decide, it is important for the expert to account for the different possibilities and scenarios, and also offer this expertise to the judge. In addition, continuing education in the analysis and interpretation of mixture DNA profiles may also be a priority for the vast majority of forensic laboratories.
authors.affiliation: Mixture Commission of the GHEP-ISFG (The Spanish and Portuguese Speaking Working Group of the International Society for Forensic Genetics), Spain; INTCF - National Institute of Toxicology and Forensic Science, Department of Barcelona, Spain. Electronic address: manuel.crespillo@mju.es.
authors.forename: M
authors.initials: M
authors.lastname: Crespillo
authors.affiliation: Mixture Commission of the GHEP-ISFG (The Spanish and Portuguese Speaking Working Group of the International Society for Forensic Genetics), Spain; INTCF - National Institute of Toxicology and Forensic Science, Department of Barcelona, Spain.
authors.forename: P A
authors.initials: PA
authors.lastname: Barrio
authors.affiliation: Mixture Commission of the GHEP-ISFG (The Spanish and Portuguese Speaking Working Group of the International Society for Forensic Genetics), Spain; INTCF - National Institute of Toxicology and Forensic Science, Department of Barcelona, Spain.
authors.forename: J A
authors.initials: JA
authors.lastname: Luque
authors.affiliation: IPATIMUP - Institute of Molecular Pathology and Immunology of the University of Porto, Porto, Portugal.
authors.forename: C
authors.initials: C
authors.lastname: Alves
authors.affiliation: Sección de Genetica Forense y Criminalística, Servicio de Laboratorio, Valencia, Spain.
authors.forename: M
authors.initials: M
authors.lastname: Aler
authors.affiliation: Department of Biomedical Sciences and Public Health, Università Politecnica delle Marche, Italy.
authors.forename: F
authors.initials: F
authors.lastname: Alessandrini
authors.affiliation: Serviço de Genética e Biologia Forenses, Delegação do Centro, Instituto Nacional de Medicina Legal e Ciências Forenses, I.P. Coimbra, Portugal.
authors.forename: L
authors.initials: L
authors.lastname: Andrade
authors.affiliation: Universidade Estadual Paulista/UNESP, Laboratorio de Investigacao de Paternidade, Sao Paulo, SP, Brazil.
authors.forename: R M
authors.initials: RM
authors.lastname: Barretto
authors.affiliation: INTCF - National Institute of Toxicology and Forensic Science, Department of Barcelona, Spain.
authors.forename: A
authors.initials: A
authors.lastname: Bofarull
authors.affiliation: Genetic Forensic Service, North Branch of the National Institute of Legal Medicine and Forensic Sciences, IP, Porto, Portugal.
authors.forename: S
authors.initials: S
authors.lastname: Costa
authors.affiliation: Servicio de Criminalística de la Guardia Civil, Laboratorio Central de Criminalística, Departamento de Biología, Madrid, Spain.
authors.forename: M A
authors.initials: MA
authors.lastname: García
authors.affiliation: Forensic Science Unit, Forensic Genetics Section, Basque Country Police, Erandio, Bizkaia, Spain.
authors.forename: O
authors.initials: O
authors.lastname: García
authors.affiliation: Laboratorio de Genética Molecular, Cruz Roja Ecuatoriana, Quito, Ecuador.
authors.forename: A
authors.initials: A
authors.lastname: Gaviria
authors.affiliation: Laboratorio de Análisis Comparativo de ADN, de la Suprema Corte de Justicia de Buenos Aires, Argentina.
authors.forename: A
authors.initials: A
authors.lastname: Gladys
authors.affiliation: Laboratorio Identificación Genética, GENOMICA SAU, Grupo Zeltia, Madrid, Spain.
authors.forename: A
authors.initials: A
authors.lastname: Gorostiza
authors.affiliation: INTCF - National Institute of Toxicology and Forensic Science, Delegation of Canarias, Santa Cruz de Tenerife, Spain.
authors.forename: A
authors.initials: A
authors.lastname: Hernández
authors.affiliation: Laboratorio Genda SA., Ciudad Autónoma de Buenos Aires, Argentina.
authors.forename: M Herrera
authors.initials: MH
authors.lastname: Piñero
authors.affiliation: Laboratorio Territorial de Biología - ADN, Brigada de Policía Científica, Jefatura Superior de Policía de Galicia, La Coruña, Spain.
authors.forename: L
authors.initials: L
authors.lastname: Hombreiro
authors.affiliation: Laboratorio de Identificación Genética - IdentiGEN, Universidad de Antioquia, Colombia.
authors.forename: A A
authors.initials: AA
authors.lastname: Ibarra
authors.affiliation: Unitat Central de Laboratori Biològic, Àrea Central de Criminalística, Divisió de Policia Científica, Policia de la Generalitat - Mossos d'Esquadra, Barcelona, Spain.
authors.forename: M J
authors.initials: MJ
authors.lastname: Jiménez
authors.affiliation: INTCF - National Institute of Toxicology and Forensic Science, Department of Madrid, Spain.
authors.forename: G M
authors.initials: GM
authors.lastname: Luque
authors.affiliation: Centro de Análisis Genéticos, Zaragoza, Spain.
authors.forename: P
authors.initials: P
authors.lastname: Madero
authors.affiliation: Laboratorio de Genetica y Identificación humana, Facultad de Medicina, Universidad de Zaragoza, Spain.
authors.forename: B
authors.initials: B
authors.lastname: Martínez-Jarreta
authors.affiliation: Bioquimica, IACA Laboratorios, Bahía Blanca, Argentina.
authors.forename: M V
authors.initials: MV
authors.lastname: Masciovecchio
authors.affiliation: Instituto de Genética Forense, Poder Judicial de Córdoba, Argentina.
authors.forename: N M
authors.initials: NM
authors.lastname: Modesti
authors.affiliation: Unidad de Genética Forense, Servicio Médico Legal, Santiago de Chile, Chile.
authors.forename: F
authors.initials: F
authors.lastname: Moreno
authors.affiliation: Laboratorio de Análisis de ADN para el CODIS, Dirección Nacional de Policía Técnica, Uruguay.
authors.forename: S
authors.initials: S
authors.lastname: Pagano
authors.affiliation: Navarra de Servicios y Tecnologias S.A.U. (NASERTIC), Pamplona, Spain.
authors.forename: S
authors.initials: S
authors.lastname: Pedrosa
authors.affiliation: NEODIAGNOSTICA, S.L., Lleida, Spain.
authors.forename: G
authors.initials: G
authors.lastname: Plaza
authors.affiliation: Laboratorio de ADN, Comisaría General de Policía Científica, Madrid, Spain.
authors.forename: E
authors.initials: E
authors.lastname: Prat
authors.affiliation: LabGenetics, Laboratorio de Genética Clínica S.L., Madrid, Spain.
authors.forename: J
authors.initials: J
authors.lastname: Puente
authors.affiliation: Sequencing and Genotyping Unit, Genomics Service - SGIker, University of the Basque Country, UPV/EHU, Bilbao, Spain.
authors.forename: F
authors.initials: F
authors.lastname: Rendo
authors.affiliation: Serviço de Genética e Biologia Forenses, Instituto Nacional de Medicina Legal e Ciências Forenses, Delegação Sul, Lisboa, Portugal.
authors.forename: T
authors.initials: T
authors.lastname: Ribeiro
authors.affiliation: Servicio de Huellas Digitales Genéticas, Fac. Farmacia y Bioquímica, University de Buenos Aires, Argentina.
authors.forename: A
authors.initials: A
authors.lastname: Sala
authors.affiliation: INTCF - National Institute of Toxicology and Forensic Science, Department of Sevilla, Spain.
authors.forename: E
authors.initials: E
authors.lastname: Santamaría
authors.affiliation: Unidad de Genética Forense, Departamento de Laboratorios, Servicio Médico Legal de Santiago de Chile, Santiago, Chile.
authors.forename: V G
authors.initials: VG
authors.lastname: Saragoni
authors.affiliation: Genomic Engenharia Molecular, São Paulo, Brazil.
authors.forename: M R
authors.initials: MR
authors.lastname: Whittle
mesh_terms: D006801:Humans; D018895:Microsatellite Repeats; D011795:Surveys and Questionnaires
keywords: Autosomal STRs; Collaborative exercise; DNA analysis; Mixture interpretation; Spanish and Portuguese-Speaking Working Group