Investigation into the effect of fingermark detection chemicals on the analysis and comparison of pressure-sensitive tapes

Abstract

Pressure sensitive tapes such as duct tape are a common trace type sent for forensic analysis. The limited variation of tape backings and adhesives can provide valuable linkage evidence between a scene, a victim or a person of interest. Fingermarks are also often found on tapes and prioritised over tape analyses. This project aimed to investigate the effects of fingermark enhancement chemicals, namely Wet Powder™, cyanoacrylate and cyanoacrylate stained with rhodamine 6G, on various tapes and their comparison with untreated tapes. The changes in physical and optical features were observed using a Video Spectral Comparator (VSC) and microscopy. Chemical changes were analysed by Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy (ATR-FTIR). Most physical and optical properties were not heavily affected by the treatments. An increase in fluorescence was observed with specimens stained with rhodamine 6G as might be expected. Significant chemical changes were observed in the FTIR spectra produced from cyanoacrylate fuming. Polyethylene backings and rubber adhesives were heavily affected while polypropylene backings were moderately affected. Cellulose backings, polyester and polyacrylate adhesives were not significantly affected. Wet Powder™ treatment proved useful for enhancing fingermarks on most adhesives while leaving behind little chemical residue that might interfere in a forensic comparison.

Keywords: Adhesive tapes; Cyanoacrylate; Fingermarks; Powder suspensions.