Analysis of Nail and Under-Nail DNA Material in Forensic Genetics

Forensic genetics significantly contributes to the resolution of various criminal cases. In addition to DNA typing, nail samples and biological materials collected from underneath the fingernails are crucial sources of evidence, especially in cases involving violence and physical struggle. In incidents such as murder, sexual assault, suicide, and disappearance, DNA analysis of biological material obtained from under the victim’s fingernails can assist in identifying suspects. Since nails are composed of keratinized cells, they contain DNA; however, isolating DNA from such cells is more challenging compared to other biological samples. Consequently, various techniques have been developed for DNA isolation from both nails and undernail materials, yet there is no consensus regarding the most effective method. Factors such as the collection technique, daily activities, transfer of material, and the presence of mixed DNA profiles significantly influence the forensic reliability of these samples. Moreover, it remains unclear whether direct analysis of nail tissue or swab samples from under the nails is more effective, or whether swabs should be collected using dry or damp cotton. There is also debate over whether nail tissues and undernail swabs should be analyzed separately or together. Additionally, forensic laboratories lack standardized protocols for the storage and transport of these samples. This study explores the forensic value and analysis methods of nail and undernail materials based on current research.