Nail as a Biological Sample in Molecular Identification of Decomposed Human Body: Case Report and Brief Literature Review

Background: Postmortem DNA identification of highly decomposed human remains is often limited by the availability and quality of conventional biological samples. Keratinized tissues, such as fingernails, represent a potentially valuable alternative due to their anatomical resistance to environmental degradation, however, their use as primary biological material for DNA profiling remains underreported in forensic practice. Case presentation: We report a case involving the recovery of a highly decomposed body of a missing woman, in which DNA samples were collected from a fingernail and a tooth. DNA extraction was performed using the PrepFiler Forensic DNA Extraction Kit for the fingernail sample and PrepFiler BTA Forensic DNA Extraction Kit for the tooth sample. No usable DNA profile was obtained from the tooth sample; however, the fingernail sample yielded a complete and high-quality STR profile with successful amplification across all 24 loci (GlobalFiler PCR Amplification Kit). Reference buccal swabs from the presumed biological parents were collected for subsequent kinship analysis. Discussion: Kinship analysis based on allele frequencies in the Croatian population resulted in a combined paternity index (CPI) corresponding to a probability of paternity of 99.99999812%, providing strong genetic support for the proposed identity of the deceased. Notably, this is the first documented forensic case in Croatia in which nail material served as the primary—and ultimately successful—biological sample for postmortem identification. Conclusions: This case highlights the evidentiary value of fingernails as a robust, accessible, and forensically valid DNA source in postmortem identification, particularly in cases of advanced decomposition where conventional biological materials are unavailable or degraded. Further studies involving larger sample sets and diverse postmortem conditions are needed to support the broader implementation of nail material in routine forensic identification workflows, particularly within the Croatian medico-legal context.