Development of latent fingerprints contaminated with ethanol on paper surfaces

Abstract

Fingerprints may be contaminated with ethanol solutions. In order to solve the case, the law enforcement agency may need to visualize the fingerprint from these samples, but the development method has not been studied. The paper with latent fingerprint was contaminated with ethanol solution and then the blurring of ridge detail was observed. As a result, when the copy paper was contaminated with ethanol solutions of less than 75 % (v/v), the amino acid components of latent fingerprint residue blurred but lipid components of latent fingerprint residue didn't blurred. On the other hand, when the paper was contaminated with ethanol solution of more than 80 % (v/v), the amino acid components of latent fingerprint didn't blurred but the lipid components of latent fingerprint blurred. Therefore, it is found that the paper contaminated with ethanol solutions of less than 75 % (v/v) should be treated by oil red O (ORO) enhancing lipid components, and the paper contaminated with ethanol solutions of 80 % (v/v) or more should be treated by 1,2-indandione/zinc (1,2-IND/Zn) enhancing amino acid components. The blurring of ridge detail was not observed when the fingerprints were deposited with fingers contaminated with ethanol solution. This fingerprints were treated with 1,2-IND/Zn or ORO to compare the latent fingerprint development ability, and using 1,2-IND/Zn was able to visualize the latent fingerprint more clearly than using ORO.