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Assigning forensic body fluids to donors in mixed body fluids by targeted RNA/DNA deep sequencing of coding region SNPs


Ingold, Sabrina; Dørum, Guro; Hanson, Erin; Ballantyne, Jack; Haas, Cordula (2020). Assigning forensic body fluids to donors in mixed body fluids by targeted RNA/DNA deep sequencing of coding region SNPs. International journal of legal medicine, 134(2):473-485.

Abstract

Biological traces found at crime scenes are analysed not only to genetically identify the donor(s) but also to determine the composition of the stain. For some cases, it is essential to associate a body fluid with a donor. Especially in mixed body fluid stains, but also in body fluid stains that appear to be single-source, this may be of importance. Linking a DNA profile (sub-source level) with evidence from a presumptive test or mRNA analysis (source level) is not straightforward. Our results support that associating donors and body fluids by means of comparing mixture ratios in RNA and DNA is not recommended. We introduce a set of 35 coding region SNPs (cSNPs) in body fluid-specific mRNA transcripts that represent a direct link between the body fluids and their donors. The discrimination power of the cSNPs was estimated based on allele frequencies calculated from a population sample (n = 188), and we investigated the practical application of the cSNPs in different scenarios. The results demonstrate that more cSNPs are needed to improve the discrimination power. However, the findings are promising as we were able to associate donors with body fluids in mixtures of different body fluids as well as in stains where both donors have contributed the same body fluid, e.g. a blood-blood mixture. In addition, the cSNP assay can be used for body fluid identification. The results of this proof-of-concept study support the use of cSNPs to assign body fluids to the respective donors.

Abstract

Biological traces found at crime scenes are analysed not only to genetically identify the donor(s) but also to determine the composition of the stain. For some cases, it is essential to associate a body fluid with a donor. Especially in mixed body fluid stains, but also in body fluid stains that appear to be single-source, this may be of importance. Linking a DNA profile (sub-source level) with evidence from a presumptive test or mRNA analysis (source level) is not straightforward. Our results support that associating donors and body fluids by means of comparing mixture ratios in RNA and DNA is not recommended. We introduce a set of 35 coding region SNPs (cSNPs) in body fluid-specific mRNA transcripts that represent a direct link between the body fluids and their donors. The discrimination power of the cSNPs was estimated based on allele frequencies calculated from a population sample (n = 188), and we investigated the practical application of the cSNPs in different scenarios. The results demonstrate that more cSNPs are needed to improve the discrimination power. However, the findings are promising as we were able to associate donors with body fluids in mixtures of different body fluids as well as in stains where both donors have contributed the same body fluid, e.g. a blood-blood mixture. In addition, the cSNP assay can be used for body fluid identification. The results of this proof-of-concept study support the use of cSNPs to assign body fluids to the respective donors.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:04 Faculty of Medicine > Institute of Legal Medicine
Dewey Decimal Classification:340 Law
610 Medicine & health
510 Mathematics
Scopus Subject Areas:Health Sciences > Pathology and Forensic Medicine
Uncontrolled Keywords:Pathology and Forensic Medicine
Language:English
Date:1 March 2020
Deposited On:01 Feb 2021 09:28
Last Modified:02 Feb 2021 21:00
Publisher:Springer
ISSN:0937-9827
OA Status:Closed
Publisher DOI:https://doi.org/10.1007/s00414-020-02252-w
PubMed ID:31989244

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