Keywords
Forensic science; Criminal investigation; Laser detection (447 nm); Color purity bandwidth (1 nm); Blue light; U.V. light; Latent saliva stains; Black color surfaces
Abstract
Rapid detecting, visualizing, and photographing latent saliva stains in the field remain as a challenge to the forensic science community. A more challenging situation is such an attempt on black color surfaces because traditional methods, e.g., blue lights and U.V. lights are usually unable to produce strong light for a better contrast. Under a quasi-experimental study, this paper reports detection and visualization of latent saliva stains on a pistol grip using three different light sources of blue light (450 nm), a U.V. light (365 nm) and a blue laser (447 nm) for a comparative purpose. The preliminary results indicate that the laser method is much superior to the blue and the U.V. lights since the laser possesses three unique technological strengths: a compact diode pump solid-state laser (447 nm wavelength), a 1 nm color-purity bandwidth, and a special yellow filter/goggle. Essentially, the laser device can detect and produce an excellent image of the latent saliva stain on the pistol grip almost simultaneously. The forensic value of the study lies in the fact that once saliva stains are located on a surface, a swab for a DNA test can follow immediately. To date, this new method may represent a new fieldbased approach to detect latent saliva stains at crime scenes. Finally, this work may progress toward the ultimate goal of rapidly detecting latent biological evidence (e.g., sweat residues) that would otherwise remain undetected using traditional development methods.
Citation
Wang JZ. Detecting Latent Saliva Stains on a Pistol Grip Using the Blue Laser (447 nm): A Comparative Study of Two Field Methods. SM J Forensic Res Criminol. 2017; 1(3): 1013.