A Non-Destructive Method for the Detection of Blood-Contaminated Fingermarks

Alfonso Bentolila, DIFS, Israel Police, Jerusalem, Israel
Michal Levin-Elad, DIFS, Israel Police, Jerusalem, Israel

Two main types of latent fingermarks may be encountered in crime scenes: amino acids based and blood contaminated. The most common reagent, which is able to develop both types of fingermarks on porous surfaces, is ninhydrin. As blood contaminated fingermarks may be crucial in connecting the suspect to the crime it is important to be able to distinguish between them and natural fingermarks. More than a decade of experience in crime scene investigations led to the understanding that there is a clear visual distinction between natural and blood contaminated fingermarks that are developed by ninhydrin. This study attempted to translate the visual difference into a mobile, non-destructive spectrophotometric method that can be used in crime scenes. Color differences between Ruhemann's purple and the reaction product of blood and ninhydrin were examined. First, color was measured by UV-vis spectra in solution. This was followed by colorimetric comparative analysis of blood contaminated vs. natural fingermarks deposited on walls and developed with ninhydrin. The comparative colorimetric analysis can provide a potentially fast, accurate and non-destructive field test for blood determination at the crime scene