An evaluation of the effect of powders on fingermarks developed with cyanoacrylate fuming

The use of cyanoacrylate (CA) fuming for the detection of fingermarks is generally followed by a secondary process such as dye staining or powdering. This study presents Phase 2 trials with planted fingermarks across five enhancement sequences comparing the use of basic yellow 40 (BY40) dye staining and a variety of powders (black magnetic powder, Bristol Black and fpNatural® 1 and 2) after cyanoacrylate fuming on two different types of plastic materials. Other variables included 10 fingermark donors, four ageing periods and 50 depletions. These trials were then followed by Phase 3 trials to assess whether the results observed in Phase 2 trials are replicated on similar plastic items typically submitted to forensic laboratories. For Phase 2 trials, the use of BY40 as secondary process to CA fuming resulted in more high-quality graded marks when compared to powdering. The fingermark grading data from the five enhancement sequences showed a significant difference with a moderate effect size. With the exception of black magnetic powder, the powdering of cyanoacrylate treated marks resulted in a detrimental effect due to infill of ridge detail. BY40 staining after the use of powders improved some of the detrimental effects; however, the use of BY40 without powders, in general, was more effective. Phase 3 trials yielded a correlation to Phase 2 trials whereby the two-step process of CA fuming with BY40 was the most effective enhancement sequence. It is therefore recommended that BY40 dye staining, rather than powders, is employed as a secondary process to CA fuming, unless the use of BY40 is not possible due to the porosity of the substrate.