ID-6-O-1766 Use of Electron Microscopy for Material Analysis in Forensic Practice

In forensic practice, electron microscopy and microanalysis rank among basic applications used in forensic investigation of traces and comparisons from crime scenes. These techniques allow for rapid screening and receiving essential information for a wide range of traces.

The set of materials that are analysed using electron microscopy is very extensive, practically any material produced by human and nature activities relating to the case that is solved can be delivered to a forensic lab (ranging from the fragment of an ancient vessel, to high-tech semiconductors). Therefore, materials of organic origin, plant and animal fragments are examined as well.

The current routine use of electron microscopy (including microanalyses) is in the following expert examinations:

- unknown samples (including powders from extortionate letters)

- mineralogical, petrological and gemmological objects (mineral relics, soils, precious stones and their imitations, etc.)

- gunshot residues (GSR)

- explosives, propellants and fulminating compounds

- post-blast residues (PBR), and other thermogenetic particles

- fillers and additives of paper and plastics

- pigments and paint systems, including colour layers of artworks

- cosmetic and pharmaceutical products (surfaces and coating layers of tablets, granular composition, phase analysis)

- morphological structures of textiles materials

- determination of sorts of damages to fibres (smelting, fibre fracture, tear/cut, fracture, etc.)

- expert examinations of biological materials - trichological material and its damage, shells of soil microorganisms, insect eggs to determine post mortem interval, etc.)

- intersecting lines of writing and print tools (superposition - writing tool x print toner)

- glass

- fragments of building materials

- fractures of materials (determination of the character of the fracture area)

- toolmark slipped impressions (forensic technical examinations, ballistics, etc.)

Recently, dual systems with focused ion beam have considerably extended possibilities of electron microscopy. These systems are predominantly applied in the study of the inner structure of micro-and nanoparticles, layers and composites (intersecting lines in forensic graphical examinations, analyses of functional glass layers, etc.), the study of alloys microdefects, creating 3D models of particles and aggregates, etc. Automated mineralogical analyses are a great asset for the analysis of mineral phases, particularly soils, analogously as cathode luminescence. TOF-SIMS systems and micro-Raman spectroscopy with a resolution comparable to standard analysis EDS/WDS are latest crucial innovations that are becoming to appear also at ordinary laboratories.