Aplicação das técnicas de exames residuográfico e metalográfico em análises periciais

Abstract

Forensic expertise has an important role in the elucidation of crimes, as well as in determining the guilt or innocence of the subject being investigation, and chemistry is one of the key sciences for proving facts with often irrefutable results. The present work aims to present some laboratory methods used by forensic chemistry. Among these, we will mention the residuographic test that, after collecting residues from the possible shooter's hands, uses either the sodium rhozonate reagent to investigate the presence of lead residues or a scanning electron microscope (SEM) with energy-dispersive X-ray spectroscopy (EDS) that looks for residues of specific metallic ions with a certain morphology, in order to prove the authorship of the firearm. Another method is the metallographic revelation which is based on restoring by chemical attack, an obliterated engraving on a metallic surface, usually stolen car chassis or firearms used in crimes, using acid reagents.