The rapidly expanding field of forensic geoscience derives its roots from 19 th and early 20 th Century scientists who both influence and are influenced by literature and fictional writing. Forensic geoscience borrows much, but not all, of its precepts from geological and geomorphological analytical techniques.Fundamental differences exist between forensic geoscience and its sister disciplines, fundamental enough to make the unwary geoscientist succumb to philosophical and practical pitfalls which will not only endanger the outline of their report, but may well indeed provide false-negative or false-positive results leading to contrary or wrongful conclusions. In the law, such outcomes have devastating and untenable consequences.Forensic geoscience requires techniques of exclusion rather than inclusion and an acknowledgement that analytical techniques may be diagnostic only in very specific situations. Whether analysis of the ubiquitous or the exotic component is chosen, acknowledgement of the need for samples to be representative is required.The presentation of false-positive results or the lack of identification of sample 'contamination' is prerequisite to the application of statistical tests which must be applied in the most careful manner. The realisation of the limitations of the technique requires, wherever possible, conjunctive analysis by other truly independent techniques. Whilst personal opinion derives from experience, there is no place for assumption. Research papers in forensic geoscience are not submitted to be speculative or challenging as may be the case in many fields of geomorphology and geology. There is no place for conjecture in forensic geoscience.
A series of experiments were conducted using various types of pollen grain, powder and metal particulates to determine their persistence on a range of different types of materials. The decay curves generated in the repeated experiments all broadly conform to those obtained and already presented in the literature for fibres and glass particulates. The experiments presented in this paper were conducted for up to 647 hours for individual runs and it was found that a general rule existed that it was the material type rather than the particulate type that was the major controlling factor in the persistence of particles. For the pollen grain experiments the overall theory is sustained; there is a significant loss initially followed by a slower decay although this is not precise given the varied nature of palynomorph types. The manner by which the particulates were introduced onto the material had an initial immediate effect, however, the persistence of these particulates over longer periods of time was generally unaffected. The inference presented in these published papers (referring to glass, paint, foam, hair etc.) is that in the first instance, particulates are shed from clothing rapidly (minutes) and then subsequently shed more slowly, with varying percentages of particulates remaining after several hours. The overall effect of the decay curve appears to be one of exponential decrease. There are however, a number of factors which have been reported to affect the persistence and decay curves of small particulates and these are well summarised by Houck [6]. He considers that the size and texture of the material being transferred may affect the persistence of such trace materials and links this to the type of surface on which the material is being retained. Further, he considers whether the particulates can be easily removed (and whether a suspect has tried to remove them). Crucially, he identifies the importance of the length of time interval between the offence and recovery of the retained material and links this to the degree of activity undertaken by the suspect or the victim following particulate transfer.The experiments presented in this paper are in response to a series of specific casework requirements in which it was deemed necessary to determine the relevant transfer and persistence of small sedimentary particles (soils, natural clays, silts and 4 sands, pollen and metal particulates), from a number of different types of clothing.Specifically, this paper seeks to identify not only the transfer, persistence and relevant abundance of particulates on clothing over time, but also whether a general rule can be introduced for all such trace particles of generally similar size (less than 100m diameter) and occurrence (glass, paint, fibres, hair, soils, clays, silts, sands, pollen and other anthropogenic materials). There is a need to consider whether geoscientific trace materials act in the same, or different, manner as those anthropogenic particulates already documented in the literature. We need to inve...
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.
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