Forensic analysis: on the capability of optical sensors to visualize latent fingerprints on rubber gloves

摘要

Thin rubber gloves are worn by criminals to prevent depositing fingerprints at crime scenes and are favored because of their tight fit, allowing hands to remain dexterous. However, fingerprints may be recovered from the inside of the gloves. The high variety of glove materials does not allow for a unified forensic approach for gloves investigation. All approaches proposed so far imply intrusive destructive treatment of the evidence. In contrast, we investigate the applicability of two contactless non-destructive sensors, a chromatic white-light sensor (CWL) and a UV-VIS spectroscope (UVVS), for digitalizing latent fingerprints left on three rubber materials: vinyl, nitrile and latex. The sensors are used to explore the visibility of sebaceous fingerprints over time, with the focus on qualitative assessment of data acquisition scenarios. Experiments show that fingerprints on porous vinyl gloves become invisible to the naked eye within 15 minutes after deposition, making the substrate very challenging. Here, fresh fingerprints can be acquired only with CWL. Fingerprints on nitrile remain preserved between 2 hours and 2.5 days and can be better captured using UVVS due to the possibility of integrating images over a certain range of wavelengths. Fingerprints on non-porous latex remain almost unchanged for at least one month and can be successfully captured using either CWL or UVVS.