SEM-EDS analysis on the skin of cadavers for the detection of environmental residues: a valuable help to forensic investigations

Background and aims: in recent years the field of application of forensic disciplines has broadened with the assistance provided by other scientific disciplines such as biochemistry, botany, entomology. A clear example is the use of SEM-EDS (scanning electron microscope with an energy dispersive X-ray spectrometry) which can provide a magnification of microscopic structures and a chemical analysis of residues. It is now widely used to identify of the wounding weapon in cases of blunt, sharp force and gunshot wounds but its importance may also include the search for environmental residues. However, a thorough investigation considering the impact of SEM-EDS analysis of skin of cadavers for the assessment of environmental residues, has never been performed. Materials and methods: the assessment of environmental residues was performed on the skin of a total of 27 corpses subjected to autopsy in the Institute of Legal Medicine of Milan, recovered in different environments and in two different seasons, aged between 20 and 94 years and died for natural or traumatic causes. The experimental project first aimed at verifying possible differences in residues between covered and uncovered areas: four samples were taken from two covered areas (anterior part of the chest and back) and two from uncovered areas (hand dorsal surface and forehead) by means of a circular adhesive tape of graphite (diameter 1cm). Skin samples were coated with graphite and analyzed by Cambridge Stereoscan 360 and EDS spectrometry. Fragments of adhesive tape, not applied to the skin surface, were used as negative controls. Moreover, as further control, samples were performed in the environments where corpses were discovered. Results: a wide variability of residues can be detected on skin, sometimes related to specific events (i.e. residues of vehicles and brakes in case of car accidents): concerning single elements, covered areas showed in average less amounts of particles than the uncovered ones, especially for what concerns iron, calcium, sodium, magnesium, chrome; differences were statistically significant (p