In the last decade Forensic Investigative Genetic Genealogy (FIGG) has changed how cold cases can be solved. Briefly, FIGG methodologies involve the analysis of dense SNP data to provide higher sensitivity by detecting a larger fraction of the genome that relatives share. In this study, our goal was to evaluate the use of the AxiomTM Spain Biobank Array (Thermo Fisher Scientific), which consists of 756,834 SNPs and typically used in biomedical research, for distant kinship resolution. In this study, a total of 28 samples were analysed consisting of buccal swabs from individuals with diverse kinship degrees. Overall, 42 real kinship cases ranging from direct to 7th degree relationships were analysed, in addition to unrelated cases for false positive testing. Three statistical approaches were employed to estimate the degree of genetic relatedness between a pair of individuals, i) the KING approach  whereby kinship coefficient and IBD0, ii) detection of genomic segment using IBIS (segment approach) and iii) likelihoods where the probability of observing the genetic profiles is calculated given two competing hypotheses (likelihood approach), in the present study using FamLink2. In general, the results obtained with three methodologies agreed well and with the expected kinship relationship. Despite the KING approach failing to provide enough discrimination power to distinguish cases more distant than 3rd degree (first cousins) from unrelated ones, kinship cases up to 7th degree (third cousins) were successfully solved by the segment approach and likelihood approach. Nevertheless, the wide variety of shared centimorgan in distant kinship categories and the lack of a likelihood value in the segment approach hinders interpretation of results and their application to real forensic cases. Importantly, the use of non-representative population allele frequencies for the LR approach can lead to significant variations in the results and may ultimately yield erroneous conclusions. 

Consequently, we conclude that the optimal workflow to implement this analysis to forensic routine consists of the combination of the segment approach and the LR approach to combine the advantages of both methods and avoid possible misinterpretations of the results.

Authors

• Ana Mosquera-Miguel (Forensic Genetics Unit, Institute of Forensic Sciences, Universidade de Santiago de Compostela, Spain)
• Amaia Cabrejas-Olalla (Forensic Genetics Unit, Institute of Forensic Sciences, Universidade de Santiago de Compostela, Spain)
• Daniel Kling (Department of Forensic Genetics and Forensic Toxicology, National Board of Forensic Medicine / Department of Forensic Sciences, Oslo University Hospital, Oslo, Norway, Sweden)
• María de la Puente (Forensic Genetics Unit, Institute of Forensic Sciences, Universidade de Santiago de Compostela, Spain)
• Inés Quintela (Fundación Pública Galega de Medicina Xenómica, SERGAS / Grupo de Medicina Xenómica, Universidade de Santiago de Compostela, Spain)
• José Javier Suárez-Rama (Fundación Pública Galega de Medicina Xenómica, SERGAS / Grupo de Medicina Xenómica, Universidade de Santiago de Compostela, Spain)
• Adrián Ambroa-Conde (Forensic Genetics Unit, Institute of Forensic Sciences, Universidade de Santiago de Compostela, Spain)
• Lucía Casanova-Adán (Forensic Genetics Unit, Institute of Forensic Sciences, Universidade de Santiago de Compostela, Spain)
• Ángel Carracedo (Forensic Genetics Unit, Institute of Forensic Sciences, Universidade de Santiago de Compostela (USC) / Fundación Pública Galega de Medicina Xenómica, SERGAS / Grupo de Medicina Xenómica, USC, Spain)
• Christopher Phillips (Forensic Genetics Unit, Institute of Forensic Sciences, Universidade de Santiago de Compostela / King’s Forensics, Faculty of Life Sciences and Medicine, King’s College, London, UK, Spain)
• María Victoria Lareu (Forensic Genetics Unit, Institute of Forensic Sciences, Universidade de Santiago de Compostela, Spain)
• Andreas Tillmar (Department of Forensic Genetics and Forensic Toxicology, National Board of Forensic Medicine / Department of Biomedical and Clinical Sciences, Faculty of Medicine and Health Sciences, LIU, Sweden)