The detection of latent fingermarks on semi‐porous substrates with UV ‐C and the full spectrum imaging system ( FSIS ‐ II Kimberley Jane Williamson, Daniel Rodriguez‐Alvarez, Paul Deacon, Kevin J. Farrugia

Abstract

The use of UV‐C imaging for the detection of latent fingermarks has been reported since the 1970s; however, widespread adoption has been limited due to health and safety concerns as well as its possible detrimental effects on DNA evidence. Semi‐porous substrates may not be suitable for processing with methods recommended for porous or non‐porous substrates. This study evaluated the effectiveness of UV‐C imaging within the full spectrum imaging system (FSIS‐II) for the detection of latent fingermarks on semi‐porous substrates. Phase 2 laboratory trials and Phase 3 pseudo‐operational trials were conducted to assess fingermark quality across different donors, substrates, aging periods and depletion series with an enhancement sequence of UV‐C, UV‐A, cyanoacrylate (CA) fuming, UV‐C, UV‐A and black magnetic powder. The use of UV‐C and UV‐A imaging prior to CA fuming was ineffective. CA fuming produced relatively few high‐quality fingermarks across all variables; however, subsequent UV‐C examination increased the detection rate by up to tenfold in Phase 2 trials and fourfold in Phase 3 trials, due to enhanced scattering of UV‐C light by the CA polymer. The use of UV‐A marginally increased the number of detected marks after CA fuming. Based on effect sizes, all variables were statistically significant, with the enhancement technique exerting the greatest influence on fingermark quality. Similar trends were observed for the Phase 3 pseudo‐operational trial. This study highlights UV‐C imaging after CA fuming as one of the most effective processes for the detection of latent fingermarks on semi‐porous surfaces when dye staining is not possible.