Rapid Detection, Virtualization, and Photographing of Latent Dry Saliva Stains on Difficult Surfaces: A Field-Based Approach Using a Portable Laser Device (447 nm)
John Zheng Wang*
Rapid detection and visualization of human saliva stains is one of the challenging tasks in forensic cases, such as murder, rape, sexual assault, and child abuse. A more challenging question is to detect dry saliva stains from certain difficult surfaces, e.g. kitchen paper towels, bitten apples, or bath towels because these item surfaces are considered as absorptive, textured, and fragile materials, rendering saliva either to be evaporated or soaked quickly. The forensic value of such an attempted method lies in the fact that once saliva is detected and visualized, the sampling area can be swapped for a DNA identification. Therefore, a novel examination approach is much needed for both field and lab applications. In this paper, a quasi-experimental study was reported to detect, visualize, and photograph latent dry saliva stains on a piece of kitchen paper towel, a bitten apple, and a piece of bath towel using a new brand of a laser detector (447 nm). The preliminary results indicated that the laser method could produce a high quality of images of saliva existence almost simultaneously. Further, the portable laser device allows for a non-destructive, non-contact, and non-invasive examination. In sum, this work progresses toward the ultimate goal of rapidly detecting and visualizing human saliva on difficult surfaces in a real-time manner that would otherwise remain undetected using other traditional development methods.
