GHEP-ISFG collaborative exercise on mixture profiles (GHEP-MIX06). Reporting conclusions: Results and evaluation.

One of the main goals 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 field 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, six exercises have been organized. At the present edition (GHEP-MIX06), with 25 participant laboratories, the exercise main aim was to assess mixture profiles results by issuing a report, from the proposal of a complex mock case. One of the conclusions obtained from this exercise is the increasing tendency of participating laboratories to validate DNA mixture profiles analysis following international recommendations. However, the results have shown some differences among them regarding the edition and also the interpretation of mixture profiles. Besides, although the last revision of ISO/IEC 17025:2017 gives indications of how results should be reported, not all laboratories strictly follow their recommendations. Regarding the statistical aspect, all those laboratories that have performed statistical evaluation of the data have employed the likelihood ratio (LR) as a parameter to evaluate the statistical compatibility. However, LR values obtained show a wide range of variation. This fact could not be attributed to the software employed, since the vast majority of laboratories that performed LR calculation employed the same software (LRmixStudio). Thus, the final allelic composition of the edited mixture profile and the parameters employed in the software could explain this data dispersion. This highlights the need, for each laboratory, to define through internal validations its criteria for editing and interpreting mixtures, and to continuous train in software handling.

A GHEP-ISFG collaborative study on the genetic variation of 38 autosomal indels for human identification in different continental populations.

A collaborative effort was carried out by the Spanish and Portuguese Speaking Working Group of the International Society for Forensic Genetics (GHEP-ISFG) to promote knowledge exchange between associate laboratories interested in the implementation of indel-based methodologies and build allele frequency databases of 38 indels for forensic applications. These databases include populations from different countries that are relevant for identification and kinship investigations undertaken by the participating laboratories. Before compiling population data, participants were asked to type the 38 indels in blind samples from annual GHEP-ISFG proficiency tests, using an amplification protocol previously described. Only laboratories that reported correct results contributed with population data to this study. A total of 5839 samples were genotyped from 45 different populations from Africa, America, East Asia, Europe and Middle East. Population differentiation analysis showed significant differences between most populations studied from Africa and America, as well as between two Asian populations from China and East Timor. Low FST values were detected among most European populations. Overall diversities and parameters of forensic efficiency were high in populations from all continents.

Data for nine autosomal STRs markers from Valencia (East Mediterranean coast of the Iberian Peninsula).

Nine STRs loci have been typed in a sample from Valencia, a population from the East Mediterranean coast of the Iberian Peninsula.

Y-chromosome STR haplotypes from a Western Mediterranean population sample.

Nine Y-chromosome STRs were investigated in a male population sample from the Western Mediterranean region of Valencia (Eastern Spain). Complete nine Y-chromosomal STRs haplotypes were obtained in 140 individuals, among which 113 different haplotypes were observed. The most common haplotype was shared by 5% of the sample, while 99 haplotypes were unique. The gene diversity was 0.9892 and the discrimination capacity was 0.8071. Significant population differences were observed with respect to other Iberian populations, such as the Basques and Northern Portugueses.

GHEP-ISFG collaborative exercise on mixture profiles of autosomal STRs (GHEP-MIX01, GHEP-MIX02 and GHEP-MIX03): results and evaluation.

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.

Euroforgen-NoE collaborative exercise on LRmix to demonstrate standardization of the interpretation of complex DNA profiles.

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.

GHEP-ISFG proficiency test 2011: Paper challenge on evaluation of mitochondrial DNA results.

The GHEP-ISFG Working Group performed a collaborative exercise to monitor the current practice of mitochondrial (mt)DNA reporting. The participating laboratories were invited to evaluate a hypothetical case example and assess the statistical significance of a match between the haplotypes of a case (hair) sample and a suspect. A total of 31 forensic laboratories participated of which all but one used the EMPOP database. Nevertheless, we observed a tenfold range of reported LR values (32-333.4), which was mainly due to the selection of different reference datasets in EMPOP but also due to different applied formulae. The results suggest the need for more standardization as well as additional research to harmonize the reporting of mtDNA evidence.

Genetic data of 10 X-STRs in a Spanish population sample.

In this work, we present population genetic data of 10 X-chromosome STRs (DXS8378, DXS9898, DXS8377, HPRTB, GATA172D05, DXS7423, DXS6809, DXS7132, DXS101 and DXS6789) obtained from sample of 145 unrelated female individuals belonging to Valencia (Spain), a region located in the east of the Iberian Peninsula. All the markers studied present high genetic diversities, similar to those previously reported in other European population samples. No deviations from Hardy-Weinberg equilibrium were observed, with the exception of DXS101 locus. Allele frequencies and parameters of forensic interest for each X-STR were calculated. High mean exclusion chance and power of discrimination values were obtained by combining these 10 X-linked markers. Population comparisons (exact test of population differentiation; pairwise genetic distances) were carried out and low genetic distances were found between our sample and those from other Spanish or European regions.

Population study of eight novel Y-chromosome STRs (DYS460, DYS461, GATA-A10, GATA-C4, GATA-H4, DYS434, DYS437, DYS439) in a southeast Iberian population: looking for highly informative Y-chromosome haplotypes.

The present study analyses 8 recently described tetranucleotide microsatellites (DYS460, DYS461, GATA-A10, GATA-C4, GATA-H4, DYS434, DYS437, DYS439) in southeast Spain and out of a total of 76 individuals 67 showed different haplotypes. Out of the 67 different haplotypes, 63 were present once, 3 were found 2 times, and 1 was found 7 times (9.21%). By combining the allelic states of the present eight Y-chromosome STRs with those previously carried out on the same individuals, highly informative haplotypes could be obtained. The haplotype diversity using the basic set of Y-STRs (DYS19, DYS389-I, DYS389-II, DYS390, DYS391, DYS392, DYS393, DYS385 and DYX156Y) previously analyzed is 0.9844. For the same individuals, this value using the new set of Y-STRs is slightly lower (0.8949), while the haplotype diversity combining the two sets of primers significantly increase to 0.9868. The results obtained in the present work show the usefulness of these microsatellites for individual identification and paternity testing in forensic genetics.

Factores que afectan al análisis biológico de las muestras de agresiones sexuales / Factors that interfere the biological analysis of the samples of sexual assaults

consolidado en los últimos años integrando un amplio espectro de profesionales de distintas disciplinas que ha abierto nuevas áreas de trabajo, en la mayoría de las cuales la interpretación del resultado se basa en la comparación con un material de referencia. Este trabajo pretende exponer brevemente una revisión de la casuística de Delitos Contra la Libertad Sexual (DCLS) estudiados en los laboratorios de Biología Forense y evaluar el rendimiento de la prueba de ADN a lo largo de los años en dos aspectos: uno en las situaciones inherentes a la metodología y otro en lo que respecta al cotejo de los vestigios analizados con las muestras de referencia de los implicados. En este segundo supuesto, el no disponer de una Base de Datos Nacional de Perfiles de ADN parece ser una de las razones en la no resolución de algunos de estos casos. Desde la denuncia del delito perpetrado hasta la obtención del ansiado perfil de ADN susceptible de cotejo intervienen múltiples factores, algunos de los cuales podrían ser controlados-consensuados desde instituciones como los Institutos de Medicina Legal (IMLs) de quienes depende la toma, distribución y envío de las muestras y otros deberían ser previstos-consensuados en los propios laboratorios de análisis

The multidisciplinary concept of Forensic Sciences has been consolidated in the last years integrating a wide spectrum of professionals of different disciplines. New areas of work have been opened, in most of them the result should be interpreted by the comparison with reference samples. This work tries to briefly expose a review of the laboratory work in sexual assaults casework and to evaluate the efficiency of the applied methodology in two aspects, one in reference to the techniques itself and another one which concerns the comparison between the specimens analysed and the reference samples of suspects. The absence in Spain of a National DNA Database seems to be one of the reasons in the non resolution of some of these cases. But many other factors, from the initial report of the crime denunciation to the achievement of the DNA profiles to be compared must be considered. We have to reach a consensus in order to control the whole process from the forensic examinations carried out in the Institutes of Legal Medicine to the interpretation of the findings in the forensic laboratory