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DNA-testing for immigration cases: The risk of erroneous conclusions
Linköping University, Department of Clinical and Experimental Medicine. Linköping University, Faculty of Health Sciences.
Linköping University, Department of Clinical and Experimental Medicine. Linköping University, Faculty of Health Sciences.
Ullevaal University Hospital.
University of Oslo.
2007 (English)In: Forensic Science International, ISSN 0379-0738, Vol. 172, no 03-Feb, 144-149 p.Article in journal (Refereed) Published
Abstract [en]

Making the correct decision based on results from DNA analyses and other information in family reunification cases can be complicated for a number of reasons. These include stratified populations, cultural differences in family constellations, families with different population origin, and complicated family relations giving complex pedigrees. The aim of this study was to analyze the risk of erroneous conclusions in immigration cases and to propose alternative procedures to current methods to reduce the risk of making such errors. A simulation model was used to study different issues. For simplicity, we focus on cases which can be formulated as questions about paternity. We present an overview of error rates (of falsely included men as the true father and of falsely excluded true fathers) for fairly standard computations, and we show how these are affected by different factors For example, adding more DNA markers to a case will decrease the error rates, as will the inclusion of more children. We found that using inappropriate population frequency databases had just minor effects on the error rates, but the likelihood ratios varied from an underestimation of 100 times up to an overestimation of 100,000 times To reduce the risk of falsely including a man related to the true father we propose a more refined prior including five hypotheses instead of the two normally used. Simulations showed that this method gave reduced error rates compared with standard computations, even when the prior does not exactly correspond to reality.

Place, publisher, year, edition, pages
2007. Vol. 172, no 03-Feb, 144-149 p.
Keyword [en]
immigration casework; Bayesian; mutation model; simulation
National Category
Engineering and Technology
URN: urn:nbn:se:liu:diva-53628DOI: 10.1016/j.forsciint.2006.12.015OAI: diva2:290313
Available from: 2010-01-26 Created: 2010-01-26 Last updated: 2010-04-08
In thesis
1. Populations and Statistics in Forensic Genetics
Open this publication in new window or tab >>Populations and Statistics in Forensic Genetics
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

DNA has become a powerful forensic tool for solving cases such as linking a suspect to a crime scene, resolving biological relationship issues and identifying disaster victims. Traditionally, DNA investigations mainly involve two steps; the establishment of DNA profiles from biological samples and the interpreta-tion of the evidential weight given by theses DNA profiles. This thesis deals with the latter, with focus on models for assessing the weight of evidence and the study of parameters affecting these probability figures.

In order to calculate the correct representative weight of DNA evidence, prior knowledge about the DNA markers for a relevant population sample is required. Important properties that should be studied are, for example, how frequently certain DNA-variants (i.e. alleles) occur in the population, the differences in such frequencies between subpopulations, expected inheritance patterns of the DNA markers within a family and the forensic efficiency of the DNA markers in casework.

In this thesis we aimed to study important population genetic parameters that influence the weight of evidence given by a DNA-analysis, as well as models for proper consideration of such parameters when calculating the weight of evi-dence in relationship testing.

We have established a Swedish frequency database for mitochondrial DNA haplotypes and a haplotype frequency database for markers located on the X-chromosome. Furthermore, mtDNA haplotype frequencies were used to study the genetic variation within Sweden, and between Swedish and other European populations. No genetic substructure was found in Sweden, but strong similari-ties with other western European populations were observed.

Genetic properties such as linkage and linkage disequilibrium could be im-portant when using X-chromosomal markers in relationship testing. This was true for the set of markers that we studied. In order to account for this, we pro-posed a model for how to take linkage and linkage disequilibrium into account when calculating the weight of evidence provided by X-chromosomal analysis.

Finally, we investigated the risk of erroneous decisions when using DNA in-vestigations for family reunification. We showed that the risk is increased due to uncertainties regarding population allele frequencies, consanguinity and compet-ing close relationship between the tested individuals. Additional information and the use of a refined model for the alternative hypotheses reduced the risk of making erroneous decisions.

In summary, as a result of the work on this thesis, we can use mitochondrial DNA and X-chromosome markers in order to resolve complex relationship in-vestigations. Moreover, the reliability of likelihood estimates has been increased by the development of models and the study of relevant parameters affecting probability calculations.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2010. 55 p.
Linköping University Medical Dissertations, ISSN 0345-0082 ; 1175
National Category
Medical and Health Sciences
urn:nbn:se:liu:diva-54742 (URN)978-91-7393-420-6 (ISBN)
Public defence
2010-05-07, Elsa Brändström-salen, Campus US, Linköpings universitet, Linköping, 09:00 (English)
Available from: 2010-04-08 Created: 2010-04-08 Last updated: 2010-04-08Bibliographically approved

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Holmlund, Gunilla
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