Application of modern analytical methods in forensic geology

Abstract

Earth materials consist of minerals, stones, sediments, soils and related components. Forensic geological investigations of these materials can help the police to connect the suspect to the crime scene. Some minerals are dangerous for the environment and human health. Thus, their identification in construction materials and waste is also an important area of geoforensics. Traditionally the examination of geological materials is carried out by using different optical microscopic methods. These methods are still essential parts of the investigations, however, due to the development of instrumental analytical chemistry and material science, new methods are available for mineralogical and geochemical analysis – even for forensic purposes. The Department of Physics and Chemistry of the Hungarian Institute for Forensic Sciences (HIFS) has undergone significant development in the past decade. Many instruments, such as scanning electron microscopes (SEM-EDS), an X-ray fluorescent spectrometer (XRF), a laser- induced breakdown spectrometer (LIBS), an inductively coupled plasma mass spectrometer (ICP-MS) and an X-ray diffractometer (XRD) – are available and used for the examination of material residues, including geological ones. SEM-EDS is a powerful tool to investigate micromorphology and local elemental composition, which is practical for the identification of individual grains, such as asbestos fibres. Elemental analytical methods, like XRF, LIBS and ICP-MS are used for the examination of both local and bulk composition. The XRF and LIBS methods are semi-quantitative, but in environmental-related cases and high-precision comparisons, the ICP-MS’s truly quantitative results are necessary. By using X-ray diffraction, the investigation of minerals, inorganic and organic crystalline materials is possible, and this method supplements the results of elemental composition data and microscopic examinations. XRD is a powerful technique for the identification of unknown crystalline materials also. In summary, the use of modern analytical equipment and statistical evaluation of measured data results in more objective, scientifically established reports in forensic geology.