1. Experimental considerations of the transfer and persistence of diatoms to clothing
K.R. Scott [1, 2], R.M. Morgan [1], A. Dudley [3], V. Jones [2], N. Cameron [2], P.A. Bull [3]
[1] UCL Centre for the Forensic Sciences, Department of Security and Crime Science [2] UCL Environmental Change Research Centre, Department of Geography, [3]Oxford University Centre for the Environment
Introduction
Microscopic traces provide great evidential value in a range of forensic scenarios and criminal investigations. Since ‘every contact leaves a trace,’ experimental and practical research has increasingly considered the behavioural dynamics of various evidence types, including those within the sub disciplines of forensic botany and forensic limnology [1-6].
Diatoms are unicellular eukaryotic microscopic algal organisms, which are widely distributed and naturally abundant in a wide range of aquatic, aerial, and terrestrial ecosystems. Individual diatom species are distinguished by an ornamented silica cell wall (Image 1), whilst population assemblages allow for detailed environmental inferences – important for forensic comparison and exclusion.
Current research is considering the application of diatom analysis as a new and independent ecological technique within forensic geoscience. Various studies confirm the initial transfer of diatom particulates as evidence and support the use of an H2O2 forensic collection procedure [7][8]. This poster presents the results of multiple experiments aiming to further consider the transfer and persistence of diatoms to clothing in a range of scenarios.
Transfer
Persistence I
Introduction
Multiple experimental studies have considered the transfer of trace evidence to evidential surfaces including clothing [9][10]. Determining the extent of evidence transfer is imperative in order to ensure the appropriate collection of geoforensic evidence following a criminal event. Relevant research concluded that material type is a major influence in the transfer and preservation of pollen and metal particulates [9]. Considering that current work has thus far focused upon the transfer of diatoms to cotton trousers [7], it is important to examine the impact of alternative surface materials.
Aim
To assess the extent of diatom transfer to a range of clothing fabrics
Methods
Eight various materials (*) were attached to trousers and submerged in a river for 3 minutes. Samples were collected and a 1cm2 subsample treated with H2O2 in the lab. Microscope slides were prepared and particulates counted and identified.
(*) [1] Cotton [2] Polyester [3] Denim [4] PVC [5] Nylon [6] Viscose [7] Linen [8] Lycra
Results
Introduction
The persistence of particulate evidence is an important consideration in the pursuit of forensic geoscience. Research has considered the impact of temporal decay upon the availability and quality of a range of materials for forensic analysis including pollen [3], hair [11], glass [12], and fibres [13]. Preliminary findings from previous work [7] indicated the continued presence of diatom particulates following intense chemical and mechanical treatments. These findings suggest the potential for the appropriate recovery and analysis of diatoms over longer time intervals.
Aim
To determine the preservation of diatom particulates following an extended period of wear
Methods
Large sections of fabric were attached to trousers and submerged in a river for 3 minutes. An initial 1cm2 transfer sample was collected and the remaining fabric attached to trousers and worn for a period of up to a week (168 hours). Persistence samples were collected at regular intervals (*). All samples were treated by H2O2 and examined under Binocular Microscopy.
(*) 30 minutes, 1 hour, 2 hours, 4 hours, 8 hours, 16 hours, 24 hours, 48 hours, 72 hours, 168 hours.
Results
More diatoms are found to transfer to Cotton and Viscose garment samples
Fewer diatoms were recorded in Lycra, Nylon, and PVC samples
The majority of diatoms transferred and recovered on each garment tend to be whole in their form allowing for accurate species identification
Of the diatoms recovered from each garment sample <30% are recorded as fragmented or <10μm in size
Centric diatoms are commonly found in abundances of 28-51% in all samples
Temporal decay in the number of diatoms recovered in a sample is observed in all 3 materials
Diatoms are still recovered following one week of wear
Trends are similar to those observed with the persistence of other types of geoforensic evidence
Irregularities in the data suggest the possible redistribution of diatom particulates on clothing
Fewer centric diatoms and more fragmented diatoms are found over longer time intervals
Persistence II
Implications
Introduction
Forensic realities often deal with the attempted destruction of evidence. Experimental research can provide vital empirical data to support the use of geoforensic techniques (such as pollen analysis) when the quality of an evidential surface may be compromised [14][15]. Diatoms are extremely resistant to chemical and mechanical stress suggesting their potential forensic application following attempt evidence disposal.
Aim
To examine the extent of diatom preservation following various stages of fire damage to clothing.
Methods
Large sections of cotton t-shirt were submerged in a clean diatom solution for 3 minutes, removed, and dried. 1cm2 subsamples were then subject to various stages of fire treatment (*) in an attempt to destroy the clothing surface. Clothing remnants and/or ash were then adhered to SEM stubs and examined under high powered microscopy. A control sample was analysed.
(*) Stage I : 5 seconds of fire; Stage II: singed material; Stage III: charred material; Stage IV: ash
Results
The studies presented in this poster highlight the role of preliminary experimental research in providing the necessary intelligence to appropriately direct case work and accurately interpret evidential outcomes:
The results observe the spatial and temporal availability of diatoms as geoforensic evidence in a range of scenarios. Analysis of samples from various garments suggests that fabric type is a limiting factor in the transfer and collection of diatom samples.
Importantly, the preservation of diatoms following attempted fire disposal and wear over a period of one week (168 hours) highlights the potential for diatoms to be collected and analyzed over the longer time scales which often accompany a criminal investigation.
Further research is needed to consider the persistence of multiple diatom transfers from a range of environments and to understand the potential redistribution of evidence apparent in the results above. Such research can contribute important findings and contribute towards the foundations of a standardized protocol for the collection and ecological analysis of evidential material.
Transfer
Collection
Persistence
Analysis
Interpretation
Presentation
Diatoms are found to persist following various levels of exposure to fire
Traces of diatoms were recovered following the complete disposal of evidence (Stage IV)
The greatest loss of evidence occurs between Stage III and Stage IV
Diatoms prove resistant to the mechanical stress of fire exposure
REFERENCES
[1] D.C. Mildenhall, "Hypericum pollen determines the presence of burglars at the scene of a crime: An example of forensic palynology." Forensic Science International 163 (2006): ; [2] P.E. Wiltshire, “Consideration of some taphonomic variables of relevance to forensic palynological investigation in the United Kingdom.” Forensic Science International 163 (2006) ; [3] R.M. Morgan, E. Allen, T. King, & P.A. Bull, “The spatial and temporal distribution of pollen in a room: Forensic implications.” Science & Justice 54 (2014) 49-56; [4] P.A. Siver, W.D. Lord, & D.J. McCarthy, “Forensic limnology: the use of freshwater algal community ecology to link suspects to an aquatic crime scene in southern New England.” Journal of Forensic Sciences 39 (1994) ; [5] M.S. Pollanen, C. Cheung, & D.A. Chiasson, “The diagnostic value of the diatom test for drowning, I. Utility: a retrospective analysis of 771 cases of drowning in Ontario, Canada.” Journal of Forensic Sciences 42 (1997) ; [6] K.A. Zimmerman, & J.R. Wallace, “The Potential to Determine a Postmortem Submersion Interval Based on Algal/Diatom Diversity on Decomposing Mammalian Carcasses in Brackish Ponds in Delaware.” Journal of Forensic Sciences 53 (2008) ; [7] K.R. Scott, R.M. Morgan, V.J. Jones, & N.G. Cameron, “The transferability of diatoms to clothing and the methods appropriate for their collection and analysis in forensic geoscience.” Forensic Science International 241 (2014) ; [8] S. Uitdehaag, A. Dragutinovic, & I. Kuiper, “Extraction of diatoms from (cotton) clothing for forensic comparisons.” Forensic Science International, 200 (2010) ; [9] P.A. Bull, R.M. Morgan, A. Sagovsky, & G.J.A. Hughes, “The transfer and persistence of trace particulates: experimental studies using clothing fabrics.” Science & Justice 46 (2006) ; [10] R.M. Morgan, J.C. French, L. O'Donnell, & P.A. Bull, “The reincorporation and redistribution of trace geoforensic particulates on clothing: An introductory study.” Science & Justice 50 (2010) ; [11] J. Dachs, I.J. McNaught, & J. Robertson, “The persistence of human scalp hair on clothing fabrics.” Forensic Science International 138 (2003) 27-36; [12] T. Hicks, R. Vanina, & P. Margot, “Transfer and persistence of glass fragments on garments.” Science & Justice 36 (1996) ; [13] C.A. Pounds, & K.W. Smalldon, “The Transfer of Fibres between Clothing Materials During Simulated Contacts and their Persistence During Wear: Part II—Fibre Persistence.” Journal of the Forensic Science Society 15 (1975) 29-37; [14] R.M. Morgan, J. Flynn, V. Sena, & P.A. Bull, “Experimental forensic studies of the preservation of pollen in vehicle fires.” Science & Justice 54 (2014) ; [15] R.M. Morgan, M. Little, A. Gibson, L. Hicks, S. Dunkerley, & P.A. Bull, “The preservation of quartz grain surface textures following vehicle fire and their use in forensic enquiry.” Science & Justice 48 (2008)