Source level interpretation of mixed biological stains using coding region SNPs

Guro Dørum; Øyvind Bleka; Peter Gill; Cordula Haas

doi:10.1016/j.fsigen.2022.102685

Source level interpretation of mixed biological stains using coding region SNPs

Forensic Sci Int Genet. 2022 Jul:59:102685. doi: 10.1016/j.fsigen.2022.102685. Epub 2022 Mar 20.

Authors

Guro Dørum¹, Øyvind Bleka², Peter Gill³, Cordula Haas⁴

Affiliations

¹ Zurich Institute of Forensic Medicine, University of Zurich, Switzerland. Electronic address: guro.dorum@irm.uzh.ch.
² Forensic Genetics Research Group, Department of Forensic Sciences, Oslo University Hospital, Norway.
³ Forensic Genetics Research Group, Department of Forensic Sciences, Oslo University Hospital, Norway; Department of Clinical Medicine, University of Oslo, Norway.
⁴ Zurich Institute of Forensic Medicine, University of Zurich, Switzerland.

PMID: 35381476
DOI: 10.1016/j.fsigen.2022.102685

Abstract

The association of body fluids/cell types and donors in mixed biological traces is an important, but challenging task required to evaluate the value of evidence given forensic propositions concerning the source of the DNA. The linking of a DNA profile with evidence from presumptive tests or RNA analysis is not straightforward. Coding region SNPs (cSNPs) are a novel type of evidential markers that are both cell type specific and individual specific. They thereby provide a direct link between a donor and a body fluid in mixed biological stains. In this proof-of-concept paper we consider the evaluation of cSNP profiles given source level propositions and explore the use of the open-source software EuroForMix to compute likelihood ratios. The discrimination power of the cSNPs for various body fluids is investigated with simulations. We provide case examples where the type of biological material is questioned and where cSNP profiles can be used to assign a donor to a body fluid, and discuss how the results can be reported in court.

Keywords: Body fluid identification; Body fluid mixtures; Coding region SNP (cSNP); Forensic Science; Likelihood ratio; Source level propositions; mRNA.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Body Fluids* / chemistry
DNA / analysis
DNA Fingerprinting / methods
Forensic Genetics* / methods
Humans
Polymorphism, Single Nucleotide

Substances

DNA