Development of Latent Finger- and Palm Marks on Non-Porous Synthetic Papers Using Alizarin Red Lake and Ninhydrin

Abstract

The development of latent fingermarks on non-porous synthetic papers using chemical reagents remains a significant challenge in forensic chemistry due to the unique physical and chemical properties of these substrates. In this study, Alizarin Red Lake, in powder form (solid), is used for the first time to develop and visualize latent fingermarks on synthetic papers. The effectiveness of Alizarin in developing and visualizing latent fingermarks and palm marks was compared to that of ninhydrin. Various synthetic papers were employed: polyester (Premium and Select grades), polyolefin (Soft grade), and polypropylene. Ninhydrin, commonly used in fingermark development, was used in this study for comparison. The results show that Alizarin produced finger and palm marks with a distinctive reddish/burgundy color and without the use of visual enhancement, whereas ninhydrin’s results showed the characteristic Ruhlmann purple and deep blue colors after the marks were enhanced at low heat (30˚C - 40˚C) for visualization. Both reagents produced continuous ridge details, visible across the marks and under daylight, highlighting Alizarin’s potential in forensic applications involving synthetic substrates as evidence. These findings suggested that Alizarin Red Lake was a promising alternative method to ninhydrin for latent mark development on challenging non-porous synthetic papers. Future work will focus on the validation of the reagent using synthetic substrates from the real world crime scenes, a comparative study of the sensitivity of Alizarin and other chemical reagents used in the development of fingermarks, such as DFO, Black powder, etc., understand the specific reaction of fingermarks’ chemical components (sebum) with Alizarin, and the formulation of Alizarin Red Lake for a broader forensic application.