A low-cost chemical and optical approach to develop latent fingermarks on silver mirror surfaces

The development of fingermarks on reflective surfaces is often a challenge regarding the photography of images with overlapping lines, low contrast and reflections, especially considering that many forensic laboratories are supplied only with basic instrumentation for fingerprint analysis. The present study overviews these difficulties and proposes a combination of chemical and optical procedures, using low-cost products and equipment, to develop fingermarks on silver mirror surfaces. The chemical treatment promotes the delimitation of the substrate, transforming the reflective surface into a transparent surface. The results were statistically analyzed, indicating quality improvement of natural fingermarks pictures taken with standard digital camera on transparent surface. There was good observation of details and minutiae, even for samples recovered several days or weeks after deposition. The suggested method substantially modifies the composition of the substrate without any contact with the fingermark, preserving its characteristics and properties. Like other nondestructive methodologies, this approach could be prioritized over methods that directly change the evidence itself and allows for the photography of the fingermark in unaltered condition. Lastly, it does not impact on the efficiency of subsequent exams.