A controlled approach to investigate the transfer and persistence of fibres encountered in forensic science

Textiles and fibres are ubiquitous in contemporary society and can be found in a variety of everyday objects and items, including textiles, surfaces, floors, and vehicles. As a result, fibres that have transferred from donor materials to recipient surfaces may be retrieved during a forensic investigation. The interpretation of fibre evidence does however necessitate an in-depth understanding of the mechanisms that could explain the presence of fibres on the recipient surface. Some of this understanding can be gained by evaluating the specific activities that could explain the transfer of fibres on the recipient surface. This thesis investigates areas of the transfer and the persistence of fibres to a recipient that are underrepresented in the scientific literature. A scientometric analysis of the existing literature was first conducted, which involved comparing the content of references cited in the INTERPOL International Forensic Science Managers Symposium reports with a combined list of references from the citation databases Scopus and Web of Science. This analysis revealed research gaps, particularly with regard to the activities leading to the transfer and persistence of fibres. The review of the literature content also highlighted the lack of consistency in the employed experimental protocol as well as the paucity of research in several areas, including the effect of washing activity on fibre transfer and persistence, and the study of recycled textiles. In this research, a method was created to investigate the effect of washing activity on the transfer and the persistence of fibres. A low-cost transfer device was developed to collect data under specific and controlled conditions. The results presented in this thesis revealed that the number of transferred fibres from cotton garments (standard virgin cotton and recycled textiles) first saw an increase in fibre count in the first few washes, before decreasing and reaching a low plateau level in the subsequent washes. This work also revealed that fibres persist in a washing machine and can transfer to other garments in subsequent washes. The composition of the donor textile was found to affect the persistence of fibres during washing, with a greater number of persisting fibres from standard virgin cotton donor garments than a textile containing recycled cotton. This work also highlighted the importance of specifying, when subsequently reporting results in the literature, the condition of the garments and the number of times they have been washed prior to the transfer studies