Soil Forensics and geological (trace) evidence

Forensic Pedology is a branch of Forensic Geology which looks for, studies and analyzes soil traces which are connected to a crime, in order to help a judicial investigation. As soil can be transferred from place to place on movable surfaces (shoes, tyres, clothes, etc.) it provides important information in connecting a person under investigation to a site; or it can shed light on the dynamics of a crime. For example, in a case where the victim of a homicide has been removed from the scene of the crime and taken to another site, soil analysis can provide useful indications to connect the victim, the vehicle by which he/she was transferred, the sites and the suspect. However, one must not forget that soil has a complex system and is comprised of several microscopic components, which have formed and developed during its long genesis and evolution. This process depends on a multitude of factors, namely topography, the climate, the typology of its parent rock, tectonics, erosion, the environment of sedimentation, the anthropogenic activity and the typology of organic substances. Because of this complexity it’s easy to note considerable differences among soil samples even when the soil is considered to be homogenous, to the point that soil components and their reciprocal ratio report variations in small areas. For this reasons, the pedological analysis are an excellent tool in supporting judicial investigations.

Forensic Geophysics and Search

Forensic Geophysics is the study, the search, the localization and the mapping of buried objects or elements beneath the soil or the water, using geophysics tools due to legal purposes. There are various geophysical techniques for forensic investigations in which the targets are buried and have different dimensions (from weapons or metallic barrels till human burials and bunkers). Geophysical methods have the potentiality to aid the search and the recovery of these targets, because they can investigate non-destructively and rapidly large areas where a suspect, illegal burial or, in general, a forensic target was tried to hide in the subsoil. When in the subsurface there is a contrast of physical properties between a target and the material in which it is buried, it is possible to individuate and define precisely the concealing place of the searched target. It is also possible to recognize evidences of human soil occupation or excavation, both recent and older.

Forensic Geochemistry

Forensic geochemistry is a branch of geology consists of collecting, analyzing and studying crime-related geological samples, in order to help a judicial investigation. Geochemical signatures provide key information on the origin and nature of pollutants. They track pollutants and interaction processes among them in different environmental matrices (emissions into air, water and soil).

Forensic geochemistry can be used to reveal environmental crimes such as pollution of groundwaters, soils and emissions of harmful substances into the atmosphere. It is also a powerful tool to support traditional investigation methods in case of violent crimes and thefts.

Isotopic composition of geological material can be considered as the “DNA” of the material itself (i.e. rock, mineral, groundwater) recording a unique signature. It has been widely used in geochemistry to identify various sources of material and processes and can provide relevant information to shape the criminal dynamic.

Image analysis has become one of the most valuable tools in forensic sciences. It is able to reveal subtle traces not visible to the naked eye but highly relevant for crime reconstruction.

Geotechnical Forensics

In the scenarios with respect to the practice of human works in the geotechnical/geological context where they are located, sometimes you have different conditions and performance compared to those expected at the design stage. This may be mainly due to deficiencies in construction materials or to an incorrect evaluation of geotechnical parameters or an inadeguate phase of geotechnical design.

The latter, as also indicated in the existing legislation, should include the characterization and the geological modeling of the site of the action, the planning and the execution of appropriate geotechnical research in situ and in laboratory, the physical-mechanical characterization of soils and rocks and the definition of a geotechnical model that will provide the designer with basic elements for security checks in relation to the work and the considered scenarios.

The technical consultant is brought in relation to two typical situations: collapse (shown, incipient or suspected) or geotechnical damage to the system. In the first case the consultant will proceed to verify the causes of the event (strictly geotechnical or structural), the second case he will analyze the impact of ongoing deformation (eg. subsidence of the ground) in elevation on the structure (very common in urban environment). The consultant frames the state of affairs from a geometrical point of view, spatial and temporal, he analyzes the technical and administrative documents, defines additional investigations or replacement of those already available, als in view of a subsequent recovery program of the site. Finally he provides a technical report which gives solid elements of technical opinion in the trial stage.

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