The persistence of animal hairs in the forensic context

This study investigated the persistence of animal hairs (cat and dog) on garments by examining variables such as different types of animal hair, different fabric types and differences in fabric features. Hair/fabric interactions were found to be far more complex than previous research had indicated. Three factors were identified that appeared to account for the majority of the differences in persistence. These factors were fibre type, yarn or knit tightness and the presence or absence of surface fibres on the recipient fabric. For example, the fabric type and the structure of the garment were shown to be integral to the mechanism of hair persistence. Structure in terms of knit variation or yarn tightness and fabric type such as wool with surface fibres appeared to exert the most influence on the retention of the animal hair on a particular garment. Wool garments had a much shallower initial decay where 82% of the hairs remained after 30 minutes, as opposed to polyester garments that exhibited a deep initial decay where only 25% of the hairs remained after 30 minutes. The initial loss – between 0–30 minutes – of hairs from all fabrics is much more rapid than the loss of hairs over all other times. Fabrics such as cotton and polyester appear much less retentive than wool and acrylic.