Measurement of soil characteristics for forensic applications

Abstract

Soils may constitute evidence that connects a person or object to a particular location. The value of soil stems from its ubiquity and transferability to objects or persons. Due to the complexity of soil, the analysis of its inorganic and organic components can provide complementary and independent types of information about its geological origin, dominant vegetation, management and environment. We present an overview of a range of soil characterisation methods including chemical analysis, mineralogy and palynology, along with new approaches such as DNA profiling and profiling of other digital data such as that obtained from X-ray powder diffraction, infrared spectroscopy and organic marker analysis.Individual analytical techniques have different scales of resolution and relevance depending on the nature of the criminal case and context. Each method has its strengths and weaknesses. As more methods have become digital and quantitative, their use in combination as digital profiles will help to characterise soils more accurately and at different scales. These new approaches can be tested using existing soil databases, and database development and use will help to refine and narrow probable origin of a questioned sample in police intelligence, as well as giving increasingly robust sample comparisons for evidence.

High Performance Liquid Chromatography as a valuable tool for geoforensic soil analysis

“…This offers potential for false positive or false negative results since components acquired before, during and after a forensic event can become mixed 16−18,24−26 . Furthermore, many existing techniques require sample quantities in excess of the materials recovered from items of forensic interest, such as shoes, clothing or vehicles 5,[20][21][22]24,26 . It is, therefore, valuable to develop analytical methods that take into account these specific requirements of forensic casework 27 .…”

Soil Chemical Insights Provided through Vibrational Spectroscopy

“…Thus, artifacts of treatment in subtraction spectra were not an unacceptable concern. This method has found continued use in soil forensics (Dawson and Hillier, 2010;Lorna et al, 2008). …”

Characterization of soils from the Algarve region (Portugal): A multidisciplinary approach for forensic applications

“…The database will provide valuable contextual information on the characteristics of the samples collected [4] that are representative and that can be comparable, allowing for exclusion within the framework of sample variability rather than inclusion [1].…”

“…Also important in forensic investigations is the comparison of questioned samples with one or more samples of known origin referenced in a database, and the quantification of the degree of similarity or dissimilarity observed between samples and its significance [1][2][3][4]. Nowadays, soil databases for forensic purposes are being developed, most of them in the UK [16,17] and in the USA [18] where geoforensics is relatively well advanced.…”

“…The ability to characterise their components at an increasing level of detail makes soil an important trace evidence for forensic investigations. Several analytical methods for soil characterization have been well established in forensic science [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15].…”