Les paramètres clés de l’interprétation des fibres textiles en sciences criminelles. Partie II: Transfert, persistance et détection

Abstract Determining the probative value of trace evidence is essential in major criminal investigations. However, this can often be difficult when the significance of the results of a particular examination have to be evaluated within the context of the framework of circumstances of a specific case. This is particularly true in criminal investigations where it is necessary to evaluate the significance of a non-differentiation between fibres from a crime scene (or a crime-related item) with a source belonging to a suspect. By employing an approach involving a probabilistic Bayesian framework, it is possible to evaluate the significance of the results of an examination by considering a set of alternative propositions relating to the alleged activity in question. In such circumstances, it is crucial that any such evaluation is carried out at activity level, since transfer and persistence of textile material may be due to an activity not related to the alleged criminal action under consideration. This article reviews the literature on the detection, transfer and persistence of textile fibres since the understanding of these three concepts is essential for the robust assessment of activity level propositions. In addition, some complex casework scenarios are discussed, including secondary transfer phenomena and the transfer of fibres during domestic violence. Finally a section dedicated to the simulation of criminal and ‘legitimate’ activities involving fibre transfer is considered, which illustrates the importance of evaluating activity level propositions using data derived from conditions as close as possible to the framework of circumstances of the actual case under consideration.