Efficiency of STR markers in complex kinship investigations

In this case report, we present the results of a complex kinship investigation involving six individuals, whose biological samples were submitted over an extended period with unclear and shifting instructions. Initially, the goal appeared to be a general reconstruction of familial relationships, yet the underlying motive remained unclear. As the genetic analyses progressed, new individuals were added, and the focus gradually shifted toward a concealed paternity issue. To clarify the familial connections among the tested individuals, we applied a combination of autosomal, X and Y-chromosomal Short Tandem Repeat (STR) markers, coupled with robust statistical methods. DNA was extracted from various personal items, and STR profiles were generated using validated forensic kits and software. Initial autosomal STR analysis primarily revealed familial relationships among three female and one male individual. The subsequent inclusion of two additional individuals not only supported the initial findings but also revealed a previously concealed paternity relationship between two of the subjects. Further analysis using X and Y-STR markers verified the autosomal STR analysis results, thereby supporting the previously established familial relationships. Despite issues like poor DNA quality in certain samples and insufficient contextual data provided, the genetic data allowed for high-confidence resolution of multiple kinship ties, including the confirmation of full- and half-sibling relationships, maternal links, and paternity. This case underscores the efficacy of molecular-genetic tools in revealing concealed familial structures and resolving disputed paternity within complex forensic contexts.