Getting the conclusive lead with investigative genetic genealogy – A successful case study of a 16 year old double murder in Sweden

Siri Aili Fagerholm,Jan Staaf,Ricky Ansell,Peter Sjölund,Andreas Tillmar

doi:10.1016/j.fsigen.2021.102525

Siri Aili Fagerholm, Jan Staaf + Show 3 more

Open Access

https://doi.org/10.1016/j.fsigen.2021.102525

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Abstract

On the morning of October 19, 2004, an eight-year-old boy and a 56-year-old woman were stabbed to death on an open street in the city of Linköping, Sweden. The perpetrator left his DNA at the crime scene, and after 15 years of various investigation efforts, including more than 9000 interrogations and mass DNA screening of more than 6000 men, there were still no clues about the identity of the unknown murderer. The successful application of investigative genetic genealogy (IGG) in the US raised the interest for this tool within the Swedish Police Authority. After legal consultations it was decided that IGG could be applied in this double murder case as a pilot case study. From extensive DNA analysis, including whole-genome sequencing and genotype imputation, DNA data sets were established and searched within both GEDmatch and FamilyTree DNA genealogy databases. A number of fairly distant relatives were found from which family trees were created. The genealogy work resulted in two candidates, two brothers, one of whom matched the crime scene samples by routine STR profiling. The suspect confessed the murders at the initial police hearing and was later convicted of the murders. In this paper we describe the successful application of an emerging technology. We disclose details of the DNA analyses which, due to the poor quality and low quantity of the DNA, required reiterative sequencing and genotype imputation efforts. The successful application of IGG in this double murder case exemplifies its applicability not only in the US but also in Europe. The pressure is now high on the involved authorities to establish IGG as a tool for cold case criminal investigations and for missing person identifications. There is, however, a continuous need to accommodate legal, social and ethical aspects as well.

Highlights

Investigative genetic genealogy (IGG) or forensic genetic genealogy (FGG) has emerged as a powerful forensic tool to generate crucial leads to identify unknown perpetrators and to identify unknown human re mains [1,2,3,4,5,6,7]
The aim of this paper is to summarize and report how IGG success fully was used in a pilot case study to solve a double murder cold case in Sweden
The suspect confessed and was later convicted for the double murder. In this case report we describe how IGG was used to obtain conclu sive investigative leads which led to the arrest and conviction of the perpetrator of a double murder cold case

Summary

Introduction

Investigative genetic genealogy (IGG) or forensic genetic genealogy (FGG) has emerged as a powerful forensic tool to generate crucial leads to identify unknown perpetrators and to identify unknown human re mains [1,2,3,4,5,6,7]. The use of microarrays nor mally requires larger amounts of DNA (in the order of hundreds of nanograms) [11]. Such a high amount of DNA is not always present in forensic samples, which instead may be in the order of nano- to subnanogram levels. Successful use of microarrays for IGG purposes has been demonstrated [2], progress in DNA sequencing technologies has significantly increased the possibility to process biological samples with degraded DNA of low quantity [15,16,17]. In this case study we used whole-genome sequencing for which standard protocols are available for as little as 50 pg of input DNA [18]

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