Abstract:
This study aimed to resolve specific issues that are associated with two fingermark enhancement techniques: cyanoacrylate (CA) fuming and fluorescent staining using the lipid dye Nile Red. A previous study showed that exposure to ozone adversely affects the enhancement of fingermarks by CA fuming. As it was hypothesized that this effect was caused by acids produced as byproducts in the oxidation processes, we investigated the use of a basic vapour pretreatment of ozone-exposed fingermarks prior to CA enhancement. Thus, charged and natural fingermarks deposited on various substrates were exposed to ozone, then subjected to ethanolamine vapour pretreatment prior to CA enhancement. Preliminary investigation of split fingermarks on glass and aluminium, aged for 0-7 days, showed the ethanolamine pretreatment to be effective in improving the CA enhancement. The method was then tested on fingermarks collected from six donors, deposited on glass, aluminium and polyethylene, and aged from 1-31 days. The overall results showed improvement in the CA enhancement of ozone-exposed fingermarks. The second objective of this study was to prepare a micro-suspension of the solvatochromic dye Nile Red in fluorous solvents. The currently used Nile Red enhancement solution is a methanol based formulation. As Nile Red is insoluble in HFE-7100 and the addition of organic solvents like methanol causes dissolution of fingermarks, an attempt was made to finely divide the Nile Red particles using ultrasound waves to form a micro-suspension in a 1:1 mixture of HFE-7100 and perfluorooctane. Preliminary investigations of staining charged fingermarks on glass and aluminium showed that the micro-suspension efficiently enhanced fingermarks that were aged up to 1 week. Comparison with enhancements produced by the methanolic formulation indicated that enhancement with the micro-suspension resulted in improved ridge details. Therefore, both the Nile Red stains were compared for fingermarks collected from four donors, deposited on glass, aluminium and polyethylene, and aged from 1-31 days. The overall results showed improved ridge details for relatively fresh fingermarks with the micro-suspension, and for 1 month old samples with the methanolic solvent. Both stains treatments showed good enhancement on glass and aluminium, however, neither enhanced fingermarks with considerable quality on polyethylene.