The detection of latent fingerprints using PCS gel on dark-colored aluminum surfaces

Abstract

Currently, the crime rate in Thailand is rising, and forensic evidence plays an increasingly important role in the justice process. Latent fingerprints are a crucial piece of forensic evidence often found at crime scenes. This research aims to detect latent fingerprints on dark-colored metal surfaces using Electrolyte Gel (PCS Gel) and to study the use of multi-wavelength flashlights to enhance the clarity of fingerprint images.  In this study, dark-colored metal surfaces, specifically taupe-colored aluminum sheets and black aluminum sheets, were used for experiments. Various formulations of electrolyte gel were prepared and used, including potassium permanganate, calcium chloride, and silica powder (PCS gel), to detect latent fingerprints on both colors of aluminum surfaces. The results showed that good-quality fingerprints were obtained using the PCS gel, which consisted of 2.5 % w/v potassium permanganate, 0.5% w/v calcium chloride , and 5 grams of silica powder in the total volume of 10 ml solution, with an optimal development time of 25 minutes. For capturing images of latent fingerprints on dark-colored surfaces, the use of multi-wavelength flashlights emitting blue light (λ = 450 nm) significantly improved the visibility of latent fingerprints and the identification of key minutiae features in low-light conditions. The findings from this research can be applied to forensic science, especially for objects with dark metal surfaces in real-life cases.