Due to recent development of modern society the thermal paper is being used more and found as evidence frequently in a crime scene. Both iodine fuming and ThermaNin® are mainly used for the development of latent fingerprints left on thermal paper. But only a few studies have been conducted to compare them directly. Therefore, the purpose of this study is to compare the efficacy of these two methods for the priority determination of development method. Several depletion series of 1st, 2nd, 3rd fingerprints from two donors (heavy donor and light donor) on the halved thermal paper were used after aged for 1, 3, 7, and 14 days, respectively. The optimal development conditions were predetermined and applied. The densitometric image analysis program CP Atals 2.0 was used to measure the areas of the peaks of fingerprint ridges for clarity.
As a result the ThermaNin® treatment demonstrated overall better and clear development than that of iodine fuming regardless of disposition and ageing condition. The iodine fuming showed variable optimum experimental condition depends on the other condition of samples and this method required continuous fuming and acquisition of images for best development. For both donors (heavy and light) iodine fuming gave higher mean areas of ridges in the depletion series of 2nd and 3rd for fresh fingerprints (day 1 and 3) compared to the aged fingerprints.
Therefore, additional experiments were necessary based on the other factors such as fingerprint donor, the deposition condition and the type of thermal paper etc. As for the proper development of latent fingerprint left on thermal paper found at a crime scene, it can be considered that ThermaNin® method has a better chance to develop good visualization result than that of iodine fuming.