FORENSIC MATERIALS IDENTIFICATION SYSTEM BY MEANS OF SCANNING ELECTRON MICROSCOPY AND ENERGY DISPERSIVE SPECTROMETRY.

There are many materials that can play an important role in a crime investigation. Some of them appear in close relation with the case, like explosives, toxics and combustibles; others are present only because circumstantial reasons, like soils, glass and fibres. It means that any kind of material and substance can appear as trace evidence in a crime. It is very important for a forensic laboratory to have the capability of determine, quickly and in an accurate way, what type of material is, for example, inside envelops, in the pockets of a suspect person, in the nails of a victim, or on a bullet. Those materials are generally small, dirty and lay on unsuited surfaces, so the capabilities of the Scanning Electron Microscopy (SEM) and Energy Dispersive Spectrometry (EDS) of magnifying and analysing small samples not destructively are very useful in these cases. The identification of minute quantities of material is not an exclusive problem of forensic sciences, it is also present for instance in medicine, in kidney stone studies 1, in characterization of minerals in petroleum investigations 2, when it is necessary to find out the nature of inclusions in gemstones 3, and in the characterization of pigments used in valuable artwork 4. But substance identification has special requirements in forensic sciences, beside the necessity of having a bi