Effects of environmental conditions to which nails are exposed on DNA analysis of them

To investigate the feasibility of DNA analysis of nails taken from human remains after environmental exposure, we tested the quantity and quality of DNA that could be recovered from nails exposed to various conditions. We first investigated whether there is an inter- or intra-subject difference in the DNA content of nails using nails obtained from 333 volunteers. DNA content did not significantly differ between males and females, or between young and elderly groups. In addition, no statistically significant differences were observed among nail samples obtained from each finger of the same person. Then thumbnails of five volunteers were left in dried soil, wet soil, river water, sea water, distilled water or air for 3 months. Each nail sample was tested monthly for sex chromosome-specific repeats, ABO genotype, STRs (TH01, TPOX, CSF1PO, FES and vWA loci), and D1S80 locus. These markers were correctly detected from nails after 1 month, irrespective of environmental conditions. Thereafter, the detection rates were decreased to various degrees, except for nails left in air. The detection of longer DNA markers tended to be more difficult than the detection of shorter markers. Nails were more fragile in wet soil than in any other condition. However, nonspecific PCR products were not observed in any nail sample. Our results reconfirmed the usefulness of the nail as a specimen for forensic DNA analysis.