Development of latent fingerprints on metallic surfaces using electropolymerization processes

We propose a new process for developing latent fingerprints on metal items, applicable to unfired weapons made of Ergal in particular. The method is b ased on the presence of fatty acids that are contained in fingerprints and act as an insulator on the surface where fingerprints are to be developed. The process of polymerization occurs on the metal portions left untouched b y finger contact. Hence, the developing process results as a negative patte rn of the original fingerprint. The reaction consists in the electropolymer ization of pyrrole and substituted porphyrins, i.e., tetra (o-aminophenyl) porphyrine: radical-cations are generated on superficial nucleation sites b y oxidation of monomer, close to the electrode surface; subsequently, the r adical species react with the neutral monomer, which begins to diffuse to t he electrode. We have also studied the polymer's morphology by means of SEM and AFM, in order to find a correlation between the reagent to be used and the quality of the enhancement process. These are only preliminary results ; however, they show that the suggested method is a new way to increase the rate of success in developing latent fingerprints on metal surfaces. In th is regard, it may be considered complementary to other conventional procedu res, due to the low costs of the instruments and reagents, and the rapidity and simplicity of the treatment.