title: Flattening mountains: micro-fabrication of planar replicas for bullet lateral striae analysis.
abstract: The application of replica molding has proven to be a valuable tool in the analysis of different forensic evidences in particular for its ability to extract the toolmarks from complex sample surfaces. A well known problem in the analysis of ballistic evidences is the accurate characterization of the lateral striae of real bullets seized on crime scenes after shots, due primarily to impact deformations and to unpredictable issues related to laboratory illumination setup. To overcome these problems a possible way is to confine over a flat surface all the features still preserving their three dimensionality. This can be achieved by a novel application of replica molding performed onto the relevant lateral portion of the bullet surface. A quasi-two-dimensional negative copy of the original tridimensional indented surface has been thus fabricated. It combines the real tridimensional topography of class characteristics (land and groove impressions) and of individual caracteristics (striae) impressed by rifled barrels on projectiles, moreover with the possibility of quantitative characterization of these features in a planar configuration, that will allow one-shot comparison of the "whole striae landscape" without the typical artifacts arising from the bullet shape and the illumination issue. A detailed analysis has been carried on at the morphological level by standard optical and scanning electron microscopy, while the 3D topography has been characterized by white light optical profilometry. A quantitative characterization of toolmarks of bullets derived from ammunitions shot by guns of large diffusion, as the Beretta 98 FS cal. 9×21 mm, has been performed and will be presented ranging between the whole landscape and the sub-μm resolution. To investigate the real potentiality of this technique, the experiment has been extended to highly impact-deformed projectiles.
authors.affiliation: Istituto per lo Studio dei Materiali Nanostrutturati (ISMN), Consiglio Nazionale delle Ricerche (CNR), Via Gobetti 101, I-40129 Bologna, Italy.
authors.forename: Laura
authors.initials: L
authors.lastname: Cominato
authors.affiliation: Istituto per lo Studio dei Materiali Nanostrutturati (ISMN), Consiglio Nazionale delle Ricerche (CNR), Via Gobetti 101, I-40129 Bologna, Italy. Electronic address: f.valle@bo.ismn.cnr.it.
authors.forename: Francesco
authors.initials: F
authors.lastname: Valle
authors.affiliation: Dipartimento di Scienze Biologiche, Geologiche ed Ambientali, Università di Bologna, Via Irnerio 49, I-40126 Bologna, Italy.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Pierini
authors.affiliation: Gabinetto Regionale di Polizia Scientifica per l'Emilia Romagna, Via Volto Santo 3, 40123 Bologna, Italy.
authors.forename: Paolo
authors.initials: P
authors.lastname: Bonini
authors.affiliation: Dipartimento di Scienze della Vita, Università di Modena e Reggio Emilia, Via Campi 183, 41125 Modena, Italy.
authors.forename: Fabio
authors.initials: F
authors.lastname: Biscarini
authors.affiliation: Gabinetto Regionale di Polizia Scientifica per l'Emilia Romagna, Via Volto Santo 3, 40123 Bologna, Italy.
authors.forename: Marcello
authors.initials: M
authors.lastname: D'Elia
mesh_terms: D004129:Dimethylpolysiloxanes; D005389:Firearms; D044709:Forensic Ballistics / Q000379:methods*; D008853:Microscopy; D008855:Microscopy, Electron, Scanning; D036103:Nanotechnology; D010363:Pattern Recognition, Automated
chemical_list: D004129:Dimethylpolysiloxanes; C013830:baysilon
keywords: Ballistic; Micro-fabrication; Nanotechnology; Profilometry; Replica molding