| 1. |
- Dorum, Guro, et al.
(författare)
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Mixtures with relatives and linked markers
- 2016
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Ingår i: International journal of legal medicine. - : SPRINGER. - 0937-9827 .- 1437-1596. ; 130:3, s. 621-634
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Tidskriftsartikel (refereegranskat)abstract
- Mixture DNA profiles commonly appear in forensic genetics, and a large number of statistical methods and software are available for such cases. However, most of the literature concerns mixtures where the contributors are assumed unrelated and the genetic markers are unlinked. In this paper, we consider mixtures of linked markers and related contributors. If no relationships are involved, linkage can be ignored. While unlinked markers can be treated independently, linkage introduces dependencies. The use of linked markers presents statistical and computational challenges, but may also lead to a considerable increase in power since the number of markers available is much larger if we do not require the markers to be unlinked. In addition, some cases that cannot be solved with an unlimited number of unlinked autosomal markers can be solved with linked markers. We focus on two special cases of linked markers: pairs of linked autosomal markers and X-chromosomal markers. A framework is presented for calculation of likelihood ratios for mixtures with general relationships and with linkage between any number of markers. Finally, we explore the effect of linkage disequilibrium, also called allelic association, on the likelihood ratio.
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| 2. |
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| 3. |
- Egeland, Thore, et al.
(författare)
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Beyond traditional paternity and identification cases: Selecting the most probable pedigree
- 2000
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Ingår i: Forensic Science International. ; 110:1, s. 47-59
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Tidskriftsartikel (refereegranskat)abstract
- The paper extends on the traditional methodology used to quantify DNA evidence in paternity or identificationcases. By extending we imply that there are more than two alternatives to choose between. In a standard paternitycase the two competing explanations H1: “John Doe is the father of the child” and H2: “A random man is the father of the child”, are typically considered. A paternity index of 100 000 implies that the data is 100 000 more likely assuming hypothesis H1 rather than H2. If H2 is replaced by “A brother of John Doe is the father”, the LR may change dramatically. The main topic of this paper is to determine the most probable pedigree given a certain set of data including DNA profiles. In the previous example this corresponds to determining the most likely relation between John Doe and the child. Based on DNA obtained from victims of a fire, bodies found in an ancient grave or from individuals seeking to confirm their anticipated family relations, we would like to determine the most probable pedigree. The approach we present provides the possibility to combine non-DNA evidence, say age of individuals, and DNA profiles. The program familias, obtainable as shareware from http://www.nr.no/familias, delivers the probabilities for the various family constellations. More precisely, the information (if any) prior to DNA is combined with the DNA-profiles in a Bayesian manner to deliver the posterior probabilities. We exemplify using the well published Romanov data where the accepted solution emerges among 4536 possibilities considered. Various other applications based on forensic case work are discussed. In addition we have simulated data to resemble an incest case. Since the true family relation is known in this case, we may evaluate the method.
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| 4. |
- Egeland, Thore, et al.
(författare)
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Beyondtraditionalpaternity and identificationcases: Selecting the most probable pedigree
- 2002
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Ingår i: Forensic Science International. ; 110:1, s. 47-59
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Tidskriftsartikel (refereegranskat)abstract
- The paper extends on the traditional methodology used to quantify DNA evidence in paternity or identificationcases. By extending we imply that there are more than two alternatives to choose between. In a standard paternitycase the two competing explanations H1: “John Doe is the father of the child” and H2: “A random man is the father of the child”, are typically considered. A paternity index of 100000 implies that the data is 100000 more likely assuming hypothesis H1 rather than H2. If H2 is replaced by “A brother of John Doe is the father”, the LR may change dramatically. The main topic of this paper is to determine the most probable pedigree given a certain set of data including DNA profiles. In the previous example this corresponds to determining the most likely relation between John Doe and the child. Based on DNA obtained from victims of a fire, bodies found in an ancient grave or from individuals seeking to confirm their anticipated family relations, we would like to determine the most probable pedigree. The approach we present provides the possibility to combine non-DNA evidence, say age of individuals, and DNA profiles. The program familias, obtainable as shareware from http://www.nr.no/familias, delivers the probabilities for the various family constellations. More precisely, the information (if any) prior to DNA is combined with the DNA-profiles in a Bayesian manner to deliver the posterior probabilities. We exemplify using the well published Romanov data where the accepted solution emerges among 4536 possibilities considered. Various other applications based on forensic case work are discussed. In addition we have simulated data to resemble an incest case. Since the true family relation is known in this case, we may evaluate the method.
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| 5. |
- Egeland, Thore, et al.
(författare)
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Estimating the number of contributors to a DNA profile
- 2003
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Ingår i: International Journal of Legal Medicine. ; 117:5, s. 271-275
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Tidskriftsartikel (refereegranskat)abstract
- The broad topic of this paper is the evaluation of DNA evidence in criminal cases. More specifically, we deal with mixture evidence which refers to cases where there are, or could be, several contributors to a biological stain based on, e.g., blood or semen. The present paper adresses DNA mixtures based on single nucleotide polymorphism (SNP) markers, i.e., diallelic markers. Based on STR analysis, it is in most cases easy to identify the presence of a mixture since three or four bands will show up with a high probability for at least one locus. Obviously, this will not be the case for diallelic markers and interpreting mixtures will be a great challenge. We address this problem by first approaching the more general problem of estimating the number of contributors to a stain. In addition we discuss how the markers should be selected and how many are required.
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| 6. |
- Egeland, Thore, et al.
(författare)
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Relationship Inference with Familias and R
- 2016
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Bok (övrigt vetenskapligt/konstnärligt)abstract
- Relationship Inference in Familias and R discusses the use of Familias and R software to understand genetic kinship of two or more DNA samples. This software is commonly used for forensic cases to establish paternity, identify victims or analyze genetic evidence at crime scenes when kinship is involved. The book explores utilizing Familias software and R packages for difficult situations including inbred families, mutations and missing data from degraded DNA. The book additionally addresses identification following mass disasters, familial searching, non-autosomal marker analysis and relationship inference using linked markers. The second part of the book focuses on more statistical issues such as estimation and uncertainty of model parameters. Although written for use with human DNA, the principles can be applied to non-human genetics for animal pedigrees and/or analysis of plants for agriculture purposes. The book contains necessary tools to evaluate any type of forensic case where kinship is an issue.
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| 7. |
- Egeland, Thore, et al.
(författare)
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Response to: DNA identification by pedigree likelihood ratio accommodating population substructure and mutations
- 2011
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Ingår i: Investigative Genetics. - : Springer Science and Business Media LLC. - 2041-2223. ; 2:7
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Tidskriftsartikel (refereegranskat)abstract
- Mutation models are important in many areas of genetics including forensics. This letter criticizes the model of the paper 'DNA identification by pedigree likelihood ratio accommodating population substructure and mutations' by Ge et al. (2010). Furthermore, we argue that the paper in some cases misrepresents previously published papers. Please see related letter: http://www.investigativegenetics.com/content/2/1/8.
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| 8. |
- Egeland, Thore, et al.
(författare)
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Statistical Genetics and Genetical Statistics: a Forensic Perspective
- 2002
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Ingår i: Scandinavian Journal of Statistics. ; 29:2, s. 297-307
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Tidskriftsartikel (refereegranskat)abstract
- This review paper focuses on forensic aspects of the relation between statistics and genetics. Some of the scientific achievements of the Swedish psychiatrist and geneticist Erik Essen-Möller may be viewed in the above interdisciplinary context. In a number of situations the correct familial relation between a group of individuals is required. We discuss recent work done to relax some assumptions involved in the classical calculations in Essen-Möller (1938). Moreover, we extend the discussion to identification problems. In a given case there may be a large number of possible family constellations or pedigrees. A prior probability distribution is established. The posterior model accounts for the combinatorial complexities of the pedigrees, mutations, kinship, and uncertainty in allele frequencies. Examples are based on the shareware program FAMILIAS, see http://www.nr.no/familias. A main message of the present paper is that the Bayesian approach is a convenient framework to down-weight unreasonable (e.g. incestuous) pedigrees that may always appear likely if only DNA-measurements are used.
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