The detection of blood, semen and saliva through fabrics: A pilot study

Abstract

This study aimed to identify if biological material could be detected on the opposite side to deposition on fabric by commonly used presumptive and/or secondary tests. Additionally, this study aimed to ascertain if there is a difference in the DNA quantity and quality from samples obtained from both sides of the same substrate: cotton, polyester, denim, or combined viscose and polyester swatches. Blood, semen, or saliva (25 μL) was deposited on one side of 5 replicates of each fabric type and left for 24 h. Blood swatches were tested using Hemastix® and the ABACard® HemaTrace® immunoassay, semen swatches were tested using acid phosphatase (AP) reagent, the ABACard® p30® immunoassay and hematoxylin and eosin staining, and saliva swatches were tested using Phadebas® paper and the RSID-Saliva™ immunoassay. Both sides of each swatch were separately wet/dry swabbed and subjected to DNA analysis. Blood was able to be detected on the underside of all fabrics using both tests. Semen was able to be detected on the underside of swatches using the presumptive AP test but not p30®, and sperm was rarely observed. Saliva was able to be detected by RSID-Saliva™ but not Phadebas® paper when the underside of swatches were tested. Across all biological materials, DNA was able to be recovered from the top side of all 60 swatches. For the underside, DNA was able to be recovered from 54 swatches. Of the 6 swatches that DNA was unable to be recovered from, one sample was from semen and the rest were from saliva. This study has demonstrated that DNA and components of interest in forensically relevant biological material can be recovered from the opposite side to where it was originally deposited, and that observing biological material and/or DNA on one side of fabric does not definitively indicate direct deposition on that side.