Effects of the most common methods for the enhancement of latent fingerprints on DNA extraction from forensic samples

The aim of the research was to understand if the use of chemicals compounds used to enhance latent fingerprints, might interfere with the extraction and amplification of DNA from biological samples on crime scenes. Only three methods were used: powders (black and white ones, used on non porous surfaces, and here applied on glass), cyanoacrylate (used on non porous surfaces, and here applied on plastic, silver, plastic-coated paper, panty hose and glass too) and DFO (only used on porous surfaces and here applied on white, colored and recycled papers). The biological samples put on surfaces included blood, saliva and fingerprints applied to all substrates by pressing for 5 s. Finds were analyzed not only upon 24 h, but also after 7, 30 and 60 days. “Untreated” samples have been used as control. DNA coming from each model was quantified by using three different kinds of techniques: the first is a qualitative one (amplification of the beta-globin gene) and the other two (Real Time PCR and Nano Drop) are quantitative. The obtained results from each sample are very similar for blood and saliva: independently from the presence of chemical compounds or trace age DNA extracted was useful for typing complete genetic profile with STR markers. Only for latent fingerprints, were noticed important differences between spectrophotometer analysis and the techniques based on PCR. To resolve these ambiguities, STR amplification and mtDNA sequencing were performed. Only mtDNA sequencing could be classified as a good technique to extract DNA from this kind of fingerprints