The preservation of quartz grain surface textures following vehicle fire and their use in forensic enquiry

Macroscopic assessment of environmental trace evidence dynamics in forensic settings

Environmental trace evidence offers useful circumstantial intelligence to link persons and scenes of forensic interest. An increasing empirical research base is dedicated towards understanding the transfer and persistence dynamics of environmental indicators including pollen, soils, and diatoms, within a diverse range of experimental frameworks. This paper presents two discrete studies exploring transfer and persistence of soils and sediments on footwear and diatomaceous earth adhered to clothing in forensically pertinent scenarios. Variables including sediment type, foot position, clothing type, and body positioning were also explored throughout. Both experiments incorporated a field-based methodology during the sampling effort. Photographs were collected of an initial transfer sample and of a retained assemblage following hours, days, and up to one-week of wear, facilitating macroscopic assessment of trace evidence dynamics. All images were processed using accessible, open-source software before spatial analysis of evidence distribution within and temporal assessment (% retention) upon each evidential surface. The results highlighted consistent loss of transferred sediment from footwear with significantly greater retention of loamy clay soil than dune sand which was absent beyond 24 h of wear. Loss was not influenced by wearer gait but was more rapid from those areas of the shoe sole in direct contact with the ground. Diatomaceous earth was retrieved from all three clothing types tested after one week - significant losses of material occurred before 48 h with a consistent assemblage identified beyond this. Denim was significantly more effective than acrylic and fleece for diatomaceous earth retention and significantly more material was lost from clothing worn on the lower body. These findings highlight the value of using visual environmental markers and a macroscopic analytical approach during the investigation of environmental trace dynamics. The methodology offers a novel, non-destructive assessment of soil and diatom transfer and persistence, complementing more extensive laboratory-based examinations to ensure the development of a well-rounded research base within the forensic sciences.

Diatoms from inland aquatic and soil habitats as indestructible and nonremovable forensic environmental evidence

Environmental analysis of soil, water, and plants plays a key role in the criminal investigation process, as it not only provides information about the course of the crime, but it can also elucidate the connection between the offender, the victim, and the environment. One particularly useful way of linking the victim and offender to a specific environment is by analyzing their clothing for the presence of diatoms. The present research was conducted upon field experiments. Firstly, it examines the variability of diatom and the quantitative analysis of diatom communities in designated places, each at an increasing distance from the aquatic ecosystem. Secondly, it analyses the differentiation of the structure of diatom communities in designated environments located close to each other. Thirdly, it examines the diatom colonization of selected substrates: cotton, chamois leather, and sponge. Finally, it confirms whether the diatoms which transfer to socks after contact with the selected environment reflect the structure of the diatom communities in that environment, even after the socks had been washed. Our findings indicate that diatom communities vary considerably, even between environments separated by short distances, and that objects placed in a particular environment are colonized by diatoms that reflect the environmental samples, irrespective of the substrate. In addition, after contact with a specific aquatic ecosystem, sock material retained diatom collections that reflected the environment samples, even though the time of exposure was very short and after the socks had been washed. This provides valuable information that can be used as forensic evidence.

Cryogenic processes and fire activity in a high Atlantic mountain area in NW Iberia (Picos de Europa) during the Mid-Late Holocene

Mid-Late Holocene environmental changes in the Cantabrian Mountains are a consequence of both climate variability and human activity. A 182cm-long sedimentary sequence was collected from Belbín depression, Western Massif of Picos de Europa (Cantabrian Mountains, NW Spain), in order to reconstruct Holocene environmental dynamics and the factors triggering landscape changes in the area. Using multi-proxy analysis of the uppermost 60cm of the sediments (texture, organic matter content, quartz grains microstructures, charcoal deposition) together with three ¹⁴C AMS dates, a sequence of alternating warmer and colder phases has been inferred for the last ca. 6.7kycalBP. Warm stages are defined by low to moderate chemical weathering of the quartz grain particles with relative increases of the C/N ratio, while colder phases show a moderate to intense physical weathering of the quartz grains and lower C/N ratios. Warmer temperatures were recorded in Belbín area between: 6.7-5, 3.7-3, 2.6-1.1, 0.87-0.51 and since 0.01kycalBP. A colder regime occurred between 5-3.7, 3-2.6, 1.1-0.87 and 0.51 to 0.01kycalBP. The increasing organic matter content during the Late Holocene may be associated with increasing temperatures. The charcoal particles do not show a higher or lower concentration during prevailing colder or warmer conditions, and therefore may be linked to human-induced fire management of the landscape. The most intense period with fire activity occurred between 3.5 and 3kycalBP during the Bronze Age.

Evaluation of particle-induced X-ray emission and particle-induced γ-ray emission of quartz grains for forensic trace sediment analysis

The independent verification in a forensics context of quartz grain morphological typing by scanning electron microscopy was demonstrated using particle-induced X-ray emission (PIXE) and particle-induced γ-ray emission (PIGE). Surface texture analysis by electron microscopy and high-sensitivity trace element mapping by PIXE and PIGE are independent analytical techniques for identifying the provenance of quartz in sediment samples in forensic investigations. Trace element profiling of the quartz grain matrix separately from the quartz grain inclusions served to differentiate grains of different provenance and indeed went some way toward discriminating between different quartz grain types identified in a single sample of one known forensic provenance. These results confirm the feasibility of independently verifying the provenance of critical samples from forensic cases.