The impact of substrate dampness on the transfer of glass fragments to upper garments when breaking windows

Abstract

Glass fragments are often recovered from garments worn by the authors of certain types of crimes and are useful as they present strong connections to the scene at both the source and activity level. It is known that the transfer of glass fragments is impacted when recipient garments are dampened, such as by rain, however, the details of the effect are not clear. This research aimed to determine the impact of substrate dampness on glass retention. Across the three test garments, a cotton t-shirt was found to increase in retentiveness with increasing dampness, while a wool/polyester blend jumper and a cotton hoodie were both found to increase only to a point, before decreasing again when the garment was saturated. This is attributed to the construction of the fabrics, as it does not appear to be related to the identity of the textile itself. It was also found that the size distribution of fragments changed with dampness. All the garments retained a smaller proportion of fragments less than 0.5 mm in size when saturated or dampened than when dry, along with an increase in the proportion of fragments in the 1–1.5 mm and greater than 1.5 mm size categories. These results indicate that is important to consider the impact of substrate dampening when relevant, and that this consideration must be done holistically as different substrates respond to dampening in different ways. It also indicates that consideration of the size distribution in fragment populations may reveal additional information in complex scenarios.