Kenneth Pye
Associates
Ltd.
Scientific Research,
Consultancy and Investigations
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Multi-technique comparison of source and primary transfer soil samples: an experimental investigation
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Abstract Croft, D.J. and Pye, K. (2004). Multi-technique comparison of source and primary transfer soil samples: an experimental investigation. Science and Justice 44(1), 21-28. The comparison of soil samples is of long-standing and increasing interest in forensic science. Routine comparisons should involve the use of several techniques in combination. A wide range of analytical techniques can be used, choice being dependent on several factors including sample size and character, time constraints and cost limitations. In this paper results are presented for experiments carried out to test the effectiveness of four of the available analytical techniques (spectro-photometric colour determination, laser diffraction particle size analysis, stable isotope analysis and chemical element analysis) used to compare single source and primary transfer soil samples. Four soil types and five footwear types were used. All four techniques showed excellent precision and good resolving power between soil types. Only relatively small differences were obtained between source and transferred soil samples in terms of colour, stable carbon and nitrogen isotope ratios and elemental chemistry. Slight but significant differences were found in grain size, indicating that the primary transfer process is to some extent grain size selective. Contact us to obtain a reprint of this paper.
Reply to correspondence Pye, K. and Croft, D.J. (2004). Multi-technique comparison of source and primary transfer soil samples: an experimental investigation - a reply. Science and Justice 44, 176-178. Introduction We are grateful for the opportunity to respond to the comments made by Bull et al. [1] on our short paper [2] dealing with multi-technique comparison of soil samples for forensic purposes. Our paper in no way attempted to provide the ‘whole story’ about forensic soil analysis; such a task would be impossible to achieve at such short length. Rather, its purpose was to provide for a mainly non-specialist readership a number of illustrative examples of the types of techniques which are now available for use in forensic soil investigations. We stated explicitly that the techniques discussed (spectrophotometric colour determination, particle size distribution analysis, major and trace element composition and light element stable isotope analysis) simply represent four of a very wide range of techniques available. These four techniques were amongst those tested in Croft’s PhD research project [3], and there was no intention in the paper to suggest that these are necessarily the most appropriate in all forensic investigations. Other techniques which might equally well have been discussed include bulk mineralogical analysis, heavy mineral analysis, clay mineral analysis, mineral magnetic analysis, radiogenic and radioactive isotope analysis, particle typology analysis, particle shape and surface textural analysis, pollen analysis and diatom analysis. As stated in our paper, the analytical requirements in each forensic case need to be assessed individually, depending on investigation objectives, sample type and availability, time and cost limitations, as well as the reproducibility and potential evidential value of the results likely to be obtained. Further information about the various alternative methods of analysis, and the potential forensic value of the results, can be found in Pye and Croft [4]. Contact us to obtain a reprint of this paper. |
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