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Subpopulation of fibres and their importance to forensic science

This study explores the significance of fiber subpopulations in forensic science and their role in determining contact between individuals. The frequency and characteristics of different fiber types are analyzed, highlighting the potential discriminating power they possess. The findings from the study conducted at London South Bank University reveal the importance of subpopulation studies in enhancing the strength of evidence in contact crimes.

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Subpopulation of fibres and their importance to forensic science

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  1. Subpopulation of fibres and their importance to forensic science Cátia Pontedeira Impression, Pattern and Trace Evidence Symposium 2018

  2. Findings of this study were not published. • These findings are part of the intellectual property of the London South Bank University • Master thesis with supervision of Sophie Park

  3. Topics covered in presentation

  4. Fibers are a very common evidence in crimes of contact (Causinet al., 2004) • Fibers can help determine if two pieces of clothing were in touch → help in the proof of contact between two individuals • The more pressured and repeated contacts, greater the transference of fibers • Transference also depends on recipient surface, area of contact and type of fibers (Pounds and Smalldon, 1975a; Roux et al., 1999) • Importance of fibers for forensic science sometimes is underestimated Importance of fibers

  5. Fiber Population Studies are framed to find the frequency of types and colors of fibers. • From the study of a certain surface we can realize which are the most common fibers • The frequency of fibers types is subject to change depending on the time of the year, weather conditions, the place or country of the study and even dependent with current fashion and habits of clothing (Was-Gubala, 2004, Cantrell et al., 2001, Watt et al., 2005) Fiber population studies

  6. The frequency of fibers will help scientists to carry out a proper assessment on the rarity of a certain fiber found in casework and to study the possibilities of that fiber haven’t been transferred by the questioned contact. Fiber population studies and their importance

  7. From the previous studies we might conclude that the most common fiber type is cotton and the most frequent colors are blue and black. • Natural fibers (animal, vegetal or mineral) are found in percentages between 80% and 87% • Wool ranges between 2% and 36% • The most common color/generic class combination is the black cotton and blue-cotton. Background research on fiber population studies

  8. Define sub-groups of a certain fiber (usually common fibers) • Comparison of the spectra obtained from the different fibers. • If two spectrums have the same shape and if the peaks are exactly in the same place, these two fibers are likely to be part of the same sub-population. • Microspectrophotometry (MSP) uses electromagnetic radiation to create the spectrum of the fibers • Biermman (2007) states that despite being a very common type of fiber, 94% of blue cottons are unique and therefore have high discriminating power. Subpopulation studies

  9. Fiber population study in London South Bank University

  10. Low Power Microscope • High Power Microscope • Comparison Microscope (different lights) • FTIR – Fourier Transform Infrared Spectroscopy • Microspectrophotometry (MSP) • More than 25 000 students • July 2013 • 10 Seats of a lecture theatre • Fibers recovered – Almost three thousand (2 958) • 571 fibers were identified as control

  11. 2 387 total fibers (excluding controls): • Most common fiber - cotton: 79% • Percentage of wool: 3% • Most common color blue: 64% • Most common generic class/color combination was: blue-black cotton (21% of population) Results

  12. Other analysis: presence of delustering, comparison between backs and seats, types of manmade fibers, cross-sections… • Subpopulation of red-pink cotton fibers • Total of red-pink fibers: 188 • Analysis using Microspectrophotometry Results

  13. Subpopulation results

  14. Subpopulation results Subpopulations had between 2 and 11 individual fibers

  15. Fibers are important in contact crimes and might help criminal investigation • Results found in London fiber population study are similar to previous studies carried out in similar conditions during summer months. • It is possible to increase strength of evidence through subpopulation studies • Even for very common type/color of fiber, fiber subpopulations studies can be very useful and greatly increase the discriminating power (given that the majority of fibers have distinctive spectra). Discussion

  16. Cantrell, S., Roux, C., Maynard, P. and Robertson, J. (2001) A textile fibre survey as an aid to the interpretation of fibre evidence in the Sydney region, Forensic Science International, 123 (2001), pp. 48-53. [Online]. Available from: Science Direct. http://www.sciencedirect.com/ [Accessed 19 August 2013] • Causin, V., Schiavone, S., Marigo, A. and Carresi, P. (2004). Baysian framework for the evaluation of fibre evidence in a double murder – a case report, Forensic Science International, 141 (2004), pp. 159-170. [Online] Available from: Science Direct. http://www.sciencedirect.com/ [Accessed 27 August 2013]. • Grieve, M. and Biermann, T. (1997) The population of coloured textile fibres on outdoor surfaces, Science & Justice, 37(4), pp. 231-239. [Online] Available from: Science Direct. http://www.sciencedirect.com/ [Accessed 15 July 2013]. • Pounds, C. and Smalldon, K. (1975a). The transfer of fibres between clothing materials during simulated contacts and their persistence during wear. Part I – Fibre transference, J. Forens. Sci. Soc., 15, pp.17-27. [Online] Available from: Science Direct. http://www.sciencedirect.com/ [Accessed 15 August 2013]. • Robertson, J. and Grieve, M. (1992) Forensic Examination of Fibres. 2nd Edition. London: Taylor & Francis. • Roux, C., and Margot, P. (1997). The population of textile fibres on cart seats, Science & Justice, 37(1), pp.25-30. [Online] Available from: Science Direct. http://www.sciencedirect.com/ [Accessed 15 August 2013]. • Was-Gubala, J. (2004) Comparative population studies of fibres secured in Poland, Czech Republic and Germany, Problems of forensic sciences, vol. LX, pp.58-77. [Online] Available from: Science Direct. http://www.sciencedirect.com/ [Accessed 15 July 2013] • Was-Gubala, J. and Chochól A. (2001) A population study of fibres found on bus seats in Cracow, Problems of Forensic Sciences, vol. XLVI, pp. 249-254. [Online] Available from: Science Direct. http://www.sciencedirect.com/ [Accessed 20 July 2013]. • Watt, R; Roux, C. and Robertson, J (2005) The population of coloured textile fibres in domestic washing machines, Science&justice, volume 45 nº2, pp. 75-83. [Online] Available from: Science Direct. http://www.sciencedirect.com/ [Accessed 20 July 2013]. Bibliography

  17. Thank you for your attention! Catia Pontedeira Criminologist - Portugal 00351 91686 3726 catiapontedeira@hotmail.com

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