Le transfert différentiel des fibres de coton et de polyester lors d’agressions au couteau

Abstract

In Canada, the knife is amongst the stabbing weapons most frequently used in the commission of violent crimes, particularly homicides. Although under-exploited, the search for fibres resulting from contact between a textile material and a receiver surface can provide relevant information on the activity at their origin. Although cotton-polyester blended textiles are among the most commonly produced worldwide, no research seems to focus on studying the proportions of fibres transferred to the knife blade during such an attack which constitutes an important lack of information for practitioners in the field. This study involved the construction of a stabbing simulation device that performed perforations under controlled parameters (e.g. force, speed and orientation of perforation) with the use of two kitchen knives with straight and serrated blades. Simulations were conducted on a set of four blended textiles to further investigate the transfer of cotton and polyester fibres and the correlation to donor textile characteristics. The transfer mainly lies on the properties of the fibres. Since cotton fibres are shorter, less resistant and less elastic than polyester fibres, they are favoured during transfer and can be found in greater proportion. Finally, the study provides some guidelines, including the addition of a scraping step, for the recovery of fibres from knife blades.