Method
Two formulations A and B were prepared. For formulation A, a suspension of 5.0 g of basic zinc carbonate in 75 ml distilled water, 100 mg basic fuchsin dye and 0.3 ml commercial liquid detergent was added. Formulation B was prepared by adding 100 mg crystal violet to a suspension of 5.0 g of basic zinc carbonate in 75 ml distilled water followed by 0.3 ml of commercial liquid detergent. About 200 ml of clean water was taken in separate containers, so as to simulate conditions of a suspected weapon recovered, from a flowing river or a stagnant pool of water, for two dye solutions, respectively. Thirty sets of three surfaces, impinged with latent fingerprints were immersed in both containers for 45 days. One set of three surfaces was taken out and sprayed with both SPR formulations separately every day for 45 days. The formulations were given one minute to react with the wetted latent fingerprint. The surfaces were washed under a gentle stream of water for 20–30 s and then dried for 40 s. Clear and sharp fingerprints could be observed as in Picture 1, Picture 2, Picture 3 and Picture 4.To determine the quality level of fingerprint development a Finger mark Quality Scale assessment33 was used Table 2.