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Gill P.,Norwegian Institute of Public Health | Gill P.,University of Oslo | Gusmao L.,University of Porto | Haned H.,Netherlands Forensic Institute | And 8 more authors.
Forensic Science International: Genetics | Year: 2012

DNA profiling of biological material from scenes of crimes is often complicated because the amount of DNA is limited and the quality of the DNA may be compromised. Furthermore, the sensitivity of STR typing kits has been continuously improved to detect low level DNA traces. This may lead to (1) partial DNA profiles and (2) detection of additional alleles. There are two key phenomena to consider: allelic or locus 'drop-out', i.e. 'missing' alleles at one or more genetic loci, while 'drop-in' may explain alleles in the DNA profile that are additional to the assumed main contributor(s). The drop-in phenomenon is restricted to 1 or 2 alleles per profile. If multiple alleles are observed at more than two loci then these are considered as alleles from an extra contributor and analysis can proceed as a mixture of two or more contributors. Here, we give recommendations on how to estimate probabilities considering drop-out, Pr(D), and drop-in, Pr(C). For reasons of clarity, we have deliberately restricted the current recommendations considering drop-out and/or drop-in at only one locus. Furthermore, we offer recommendations on how to use Pr(D) and Pr(C) with the likelihood ratio principles that are generally recommended by the International Society of Forensic Genetics (ISFG) as measure of the weight of the evidence in forensic genetics. Examples of calculations are included. An Excel spreadsheet is provided so that scientists and laboratories may explore the models and input their own data. © 2012 Elsevier Ireland Ltd. All rights reserved.

Prieto L.,University Institute of Research in Forensic science | Haned H.,Netherlands Forensic Institute | Mosquera A.,University of Santiago de Compostela | Crespillo M.,Instituto Nacional Of Toxicologia Y Ciencias Forenses | And 25 more authors.
Forensic Science International: Genetics | Year: 2014

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. © 2013 Elsevier Ireland Ltd All rights reserved.

Prieto L.,University Institute of Research in Forensic science | Alves C.,University of Porto | Zimmermann B.,Innsbruck Medical University | Tagliabracci A.,Marche Polytechnic University | And 29 more authors.
Forensic Science International: Genetics | Year: 2013

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. © 2012 Elsevier Ireland Ltd.

Montesino M.,University Institute of Research in Forensic science | Tagliabracci A.,Marche Polytechnic University | Zimmermann B.,Innsbruck Medical University | Gusmao L.,University of Porto | And 29 more authors.
Forensic Science International: Genetics Supplement Series | Year: 2011

In this GHEP-ISFG exercise, participating labs were invited to evaluate a forensic case in which the mtDNA haplotype from a hair shaft in the victim's hand matched the suspect's haplotype. 31 forensic labs participated in the exercise. Although all except one used the EMPOP database to estimate the haplotype frequencies different final likelihood ratios (LRs) were reported. The main factors affecting these differences were: the origin of the reference population, the approaches to correct sampling errors, the LR formula, the source of EMPOP data (forensic/literature), the type of search (pattern or literal and "disregard Indels" option) and the selected edition range to perform the queries. This demonstrates that further efforts are needed in order to standardize the statistical evaluation of the mtDNA evidence. © 2011 Elsevier Ireland Ltd.

Prieto L.,University Institute of Research in Forensic science | Zimmermann B.,Innsbruck Medical University | Goios A.,University of Porto | Rodriguez-Monge A.,University Institute of Research in Forensic science | And 17 more authors.
Forensic Science International: Genetics | Year: 2011

Mitochondrial DNA (mtDNA) population data for forensic purposes are still scarce for some populations, which may limit the evaluation of forensic evidence especially when the rarity of a haplotype needs to be determined in a database search. In order to improve the collection of mtDNA lineages from the Iberian and South American subcontinents, we here report the results of a collaborative study involving nine laboratories from the Spanish and Portuguese Speaking Working Group of the International Society for Forensic Genetics (GHEP-ISFG) and EMPOP. The individual laboratories contributed population data that were generated throughout the past 10 years, but in the majority of cases have not been made available to the scientific community. A total of 1019 haplotypes from Iberia (Basque Country, 2 general Spanish populations, 2 North and 1 Central Portugal populations), and Latin America (3 populations from São Paulo) were collected, reviewed and harmonized according to defined EMPOP criteria. The majority of data ambiguities that were found during the reviewing process (41 in total) were transcription errors confirming that the documentation process is still the most error-prone stage in reporting mtDNA population data, especially when performed manually. This GHEP-EMPOP collaboration has significantly improved the quality of the individual mtDNA datasets and adds mtDNA population data as valuable resource to the EMPOP database (www.empop.org). © 2010 Elsevier Ireland Ltd.

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