Sediment Fingerprints: A forensic technique using quartz sand grains

Abstract

The analyses of 738 soil and sediment samples taken during the investigation of 20 forensic cases are combined in a database for retrospective comparisons. Quartz sand grain surface textures are combined into grain types which are analysed at one of five orders of classification. This classification also provides frequency data on the number of grain types found in a sample, the individuality of the quartz grain type assemblages and quartz grain type ratios. The technique, developed primarily as an exclusion mechanism, suggests possibilities, in some circumstances, that significant interpretations can be achieved at different orders of classification. The technique provides excellent exclusionary results and, when combined with other independent lines of analysis, is a powerful tool in forensic interpretation because it uses quartz as its discriminatory mineral. The technique also highlights the potential for computer image recognition analysis.Se combinan en una base de datos, con fines de comparación retrospectiva, los análisis de 738 muestras de suelo y sedimentos tomados en la investigación de 20 casos forenses. Las texturas de superficies de arena con granos de cuarzo se combinan en tipos de grano que son analizadas como una de cinco órdenes de clasificación. Esta clasificación también prove e datos de frecuencia de los tipos de grano encontrados en una muestra, la individualidad de ensamblajes de los tipos de grano de cuarzo y los cocientes de los tipos de grano de cuarzo. La técnica, desarrollada en un principio como un mecanismo de exclusión, sugiere posibilidades en algunas circunstancias de que se pueden conseguir interpretaciones significativas en distintos órdenes de clasificación. La técnica provee resultados de exclusión excelentes y , cuando se combina con otras líneas independientes de análisis es una herramienta poderosa en interpretación forense ya que utiliza el cuarzo como mineral discriminatorio. La técnica también ensalza el potencial del análisis mediante imagen computerizada.

The role of forensic geoscience in wildlife crime detection

“…Samples taken from the badger sett site proved to be predominantly quartz which were comprised of three main quartz grain textural groupings [12]. This combination of textural groupings is not found in any of the thousand sample locations found in the paper above and so can be excluded as having derived from any previously sampled source in Britain.…”

“…This generally ubiquitous mineral, found in most soils, contains grain types (these are an amalgam of suites of grain surface features) that can vary dramatically from site to site. Bull and Morgan [12] identify that there are only a very discrete number of quartz grain types found in each sample, taken across England (n = c.1000 from which a database was constructed) and that it is possible to compare comparator grains to sample grains, and if the quartz grain types were different, then they could be excluded from having derived from the same source.…”

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

“…Furthermore, the distinctive, elongated grains observed were present at all locations. It has been demonstrated that across the UK, on average there are 2-3 distinct grain types present at a given location 42 , so the lack of diversity within these samples is distinctive, but ultimately for this study did not provide additional discriminatory information for these samples taken from different locations within the park.…”

“…Quartz grains are highly persistent and abundant in soil samples and analysis of quartz grain surface texture by SEM can be used to reconstruct the geological history of the quartz grains present in soils and sediments 41 . The technique has previously been demonstrated to be highly informative in the investigation of the provenance of geoforensic samples 18,42 and offers a number of advantages in forensic investigations since it requires very small quantities and a simple and non-destructive sample preparation, which aids the interpretation of data derived from samples comprising mixtures of material from different provenances 16 . Quartz grain surface texture analysis has been shown to work well in combination with other forensic analytical techniques in previous studies 18,25 and was, therefore, considered a good candidate for use in conjunction with HPLC.…”

Sediment fingerprints: A forensic technique using quartz sand grains — A response

“…It further enhances the ability of the experienced electron microscopist to designate the grain type after viewing 3 0-40 textures and noting their presence or absence on a grain in order that a provenance designation can be made. Of course, in the context of a forensic case this academic interpretation is not needed for a meaningful presentation of findings to the court (see our Table 2 and related discussion [1]). …”