Testing the recoverability of grass DNA transferred to textiles for forensic purpose

Abstract

Botanical evidence such as grass stains on textiles is sometimes present in the crime scene and can allow investigators to establish an association between persons linked to the criminal event and the crime scene. In this study, extraction of grass DNA from stains on textiles was undertaken. DNA extraction was performed on four grass species conserved both indoors and outdoors for 7, 14 and 30 days after staining. Once the extracted DNA was quantified, a polymerase chain reaction (PCR) amplifying a fragment of the internal transcribed spacer was performed.DNA extraction was successful in 97.5% of samples. No significant differences in the amount of extracted DNA were detected among species or stain ages. However, one grass species (Cynodon dactylon) showed a significant diminution in the mean DNA concentration between indoor and outdoor samples (439.9±137 ng/µL vs. 318.9±177 ng/µL respectively; p=0.041). PCR was successful in 89.2% of samples. This study has thus demonstrated the recoverability of grass DNA from stains on cloths and its stability in the first month after staining in both outdoor and indoor environments, as well as its suitability for PCR amplification that could allow correct species identification.

Keywords

• grass DNA
• forensic DNA analysis
• forensic science