Fleece jackets are often encountered as items of clothing submitted for examination in forensic science laboratories in Scotland. This work examines the background glass contamination of garments of this nature in order to inform casework conclusions. 44 fleece jackets (100% polyester) from individuals who either worked in the Forensic Science laboratory or were police officers who regularly attended crime scenes were examined for the random presence of glass fragments. The refractive index of recovered fragments was determined using glass refractive index measurements. The values obtained were compared with glass fragments recovered from garments associated with criminal events and the results assessed.