SNP Markers as Additional Information to Resolve Complex Kinship Cases

Abstract

Background: DNA profiling with sets of highly polymorphic autosomal short tandem repeat (STR) markers has been applied in various aspects of human identification in forensic casework for nearly 20 years. However, in some cases of complex kinship investigation, the information provided by the conventionally used STR markers is not enough, often resulting in low likelihood ratio (LR) calculations. In these cases, it becomes necessary to increment the number of loci under analysis to reach adequate LRs. Recently, it has been proposed that single nucleotide polymorphisms (SNPs) could be used as a supportive tool to STR typing, eventually even replacing the methods/markers now employed. Methods: In this work, we describe the results obtained in 7 revised complex paternity cases when applying a battery of STRs, as well as 52 human identification SNPs (SNPforID 52plex identification panel) using a SNaPshot methodology followed by capillary electrophoresis. Results: Our results show that the analysis of SNPs, as complement to STR typing in forensic casework applications, would at least increase by a factor of 4 total PI values and correspondent Essen-Möllerʼs W value. Conclusions: We demonstrated that SNP genotyping could be a key complement to STR information in challenging casework of disputed paternity, such as close relative individualization or complex pedigrees subject to endogamous relations.