Large Scale SNP Analysis for the Identification of Victims from the Spanish Civil War

Across Spain, there is a drive to identify victims from the Spanish Civil War (1936-1939). Forensic Investigative Genetic Genealogy (FIGG) relies on searching an unknown genetic profile against a global consumer database to identify distant relatives. Although FIGG has been used successfully to solve cold cases, it may not always be appropriate in situations of unidentified human remains (UHR) for legislative or ethical reasons. Additionally, in scenarios like the identification of Spanish Civil War remains, family references are often available for direct comparison. As time passes, these family references are more likely to be more and more distantly related however, requiring a large number of genetic markers for kinship analysis.

As an accredited laboratory for the use of Massively Parallel Sequencing (MPS) in forensics and working in missing persons projects from the Spanish Civil War, we have already studied more than 200 ~90 years old bone samples, obtaining genetic profiles (27 aSTRs and 25 Y STRs) from degraded and low concentrated samples (quant values ranging from 10-2 to 10-3 ng/µL) with different degradation indexes, using mainly the ForenSeq™ MainstAY kit.

Despite obtaining full STR profiles using MPS, the absence of direct relatives and even seconddegree relatives from many of the victims led to a number of inconclusive results. The 10,230 SNPs targeted by the ForenSeq Kintelligence kit, and the algorithms for kinship analysis used in GEDmatch PRO, have been repurposed into a solution for UHR processing – the Kintelligence HT kit. In this work, antemortem and postmortem samples were processed using the ForenSeq Kintelligence HT kit.

This presentation will show the first results obtained from applying this large-scale SNP set and local kinship database on the identification of victims of the Spanish Civil War. We demonstrate that even for highly degraded bones, over 8000 SNPs were typed in the majority of cases. This meant that the SNP overlap between the bone samples and relative samples remained high enough to perform robust kinship calculations, with data evaluated using kinship coefficients and LRs for stated pedigrees, allowing the identification of victims that remained unidentified even with a known full STR profile.

This technology enabled us to establish higher LR values (log10LR values over 80 for third and even fourth degree relationships) that lead to new identifications or even to confirmation of some that had been inferred indirectly through the study of lineages and anthropological and historical data, taken together.

Results show the use of ForenSeq® Kintelligence-HT as a promising strategy for the identification of highly degraded skeletal remains in missing persons cases. Moreover, the availability of phenotype, ancestry, X and Y chromosome data allows for complementary studies that, in some cases, can be crucial for identification.