Análises morfológicas, químicas e genéticas de impressões digitais aplicadas à prática forense

Abstract

The development of dactyloscopy science over the last decade has shown that the use of fingerprints for forensic purposes is not limited to traditional morphological analysis and that forensic practice can benefit from the use of other methodologies for analyzing this trace, such as genetic, physical, and chemical analysis. This triad of analyses was investigated in this work from the perspective of fingerprint dating, initially considering the microstructural and elemental analyses of fingerprints on brass plates - a metal surface of forensic interest, mainly because it is the main type of metal alloy that makes up ammunition cases, which are traces commonly found at crime scenes. These analyses were carried out using the Scanning Electron Microscopy technique coupled with Energy Dispersive X-ray Spectroscopy (SEM-EDX). Secondly, the genetic aspect was studied using DNA analysis of fingerprints on the surface of fired cartridge cases, using realistic sample production dynamics compatible with practice. The results of the SEM-EDX analysis indicated that ridges tend to widen over time and that the structural alterations of the ridges on metal surfaces may be directly related to the process of corrosion of the metal caused by the eccrine secretion constituting fingermark deposits. The data generated from EDX indicates that oxygen and chlorine could be potential markers of fingermark aging, since their relative quantities varied markedly in recent (0 days) and aged (28 days) prints. Genetic analysis indicated that 85% of the samples showed degradation and in none of them inhibition of the DNA amplification reaction was detected, resulting in a 22% success rate in obtaining genetic profiles from fingerprints under the conditions tested. The results suggest that the metal surface exerts a significant influence on the success of genetic analysis of deflagrated cases and that the possibility of obtaining a genetic profile from this type of sample, although it presents difficulties, is feasible and should not be ruled out. The combined use of techniques that make it possible to study the physical and chemical alterations of fingerprints is strongly recommended by the scientific community today, even though they may be more complex approaches, for advances in fingerprint age determination.