Fingerprint Enhancement by means of Electromagnetic Radiation: a Pilot Study to Drive Future Researches

Fingerprints are a worldwide well known tool for law enforcement agencies to reach the individualization of people convicted of a crime. Moreover, all major countries have huge fingerprint databases and efficient automated systems (AFIS) to perform electronic screening of fingerprints marks recovered by crime scene investigation. Fingerprints are permanent and even if, from a scientific point of view, they could not be considered unique, friction ridge is highly selective and allows a discrimination between different individuals with a very high proficiency. Up to now, the most common techniques for enhancing latent fingerprints from articles collected in the crime scene are based on chemical-physical processes, or optical detection techniques, based on absorption, photoluminescence, diffused reflection or ultraviolet imaging, with appropriate band-pass and/or narrow-band filtering. Chemical-physical processes have shown really good performances, but they are destructive with respect to the latent finger mark deposit and in most cases these methods partially affect subsequent DNA analysis. On the other side, optical detection processes have the advantage of being non-destructive of the fingerprint. As a result, these techniques allow later performing of DNA analysis and/or the further application of conventional fingerprint development procedures. The majority of the optical techniques, with the possible exception of the ultraviolet inspection, allow further biological analysis. And as the aforementioned methods have the advantage of being non alterative with the respect of the fingerprint deposit, subsequent application of chemical and/or physical methods is not precluded. Moreover, some recent studies are investigating the X-ray fluorescence of fingerprints, and some others are attempting to discriminate the IR spectrum of the finger mark deposit from the IR spectrum of the surface. It is easy to understand how crucial is to develop a robust technique of optical analysis, able to reach a high-resolution imaging of finger marks, requiring no chemical conventional or non-conventional pre-process and producing no modification either on the finger perspiration deposit or on the background surface. The proper image of the fingerprint, obtained from the item surface, could allow us to perform a complete fingerprint analysis, which potentially leads us to the individualization of the perpetrator. Moreover, fingerprint imaging could exactly point out the particular region of the whole surface where we can surely find the DNA of the donor, with a higher probability of successful analysis.