Human fingernails may provide valuable genetic material for forensic identification, even after exposure to elevated temperatures. A study published on 7 November 2026 in Forensic Science, Medicine and Pathology investigated the recovery of short tandem repeat (STR) profiles from thermally degraded fingernail samples.
The research, titled DNA profiling of thermally degraded nails using AmpFlSTR® MiniFiler™ PCR amplification kit, was conducted by Fawziah S. Al-Balawi, Sachil Kumar, Saranya R. Babu and colleagues.
The researchers examined 30 fingernail samples collected from 30 Saudi donors. The samples were subjected to controlled thermal exposure at 150°C for two different durations: five and ten minutes. Reference DNA was obtained from buccal swabs and non-degraded nail samples.
DNA extraction was performed using the QIAamp DNA Investigator Kit. The researchers assessed DNA quantity and quality using the Quantifiler Trio DNA Quantification Kit before conducting STR amplification with the AmpFlSTR MiniFiler PCR Amplification Kit.
The results demonstrated that heat exposure did not necessarily eliminate all recoverable genetic information. Reference buccal swabs and untreated fingernails produced complete STR profiles, while heat-treated samples showed varying degrees of genetic information loss.
In the five-minute exposure group, eight out of 30 samples produced partial STR profiles containing fewer than nine successfully recovered loci. In the ten-minute group, nine out of 30 samples produced partial profiles. Allele dropout was observed in ten samples from each heat-treated group.
Allele dropout occurs when an expected genetic allele fails to appear in the analytical profile. This can reduce the completeness of a DNA profile and complicate interpretation.
Importantly, the researchers reported no complete loss of STR profiles in the examined heat-treated samples. They also observed no allele drop-in in the negative amplification controls or analysed electropherograms.
These findings suggest that fingernails may remain a useful alternative biological material for DNA profiling when conventional samples have been exposed to heat or environmental damage.
However, the results must be interpreted cautiously. The experiment involved a limited number of donors and specific laboratory-controlled temperature and exposure conditions. Actual fire scenes involve complex environmental variables, including uneven heating, oxygen availability, moisture and differences in exposure duration.
Consequently, the findings should not be interpreted as evidence that fingernails will consistently provide identifiable DNA after exposure to real fire conditions.
The research adds to the scientific understanding of DNA persistence in keratinized biological materials and highlights the potential value of alternative biological samples in challenging forensic investigations. Further research under more varied conditions will be necessary to establish the broader forensic applicability of these findings.