Theory of a Chemical Kinetic Approach for the Estimation of the Age of Fingerprints

Abstract

Fingerprints are one of the most important forms of physical evidence in forensic investigations worldwide. The age of a fingerprint is the time at which a latent fingerprint was deposited. Unfortunately, there is a lack of reliable methods to determine the age of fingerprints. This is due to the fact that fingerprint composition changes in time through complex chemical, biological and physical processes. Chemical kinetics is the study of reaction rates and the effects of concentration, temperature, pressure and other physical factors on these rates. It establishes quantitative relationships, called rate laws, between the concentrations of reagents, products and time. Therefore, chemical kinetic rate laws allow us to determine the concentration of a given reagent at any time or the time corresponding to a given concentration. In this work we propose to use a chemical kinetic approach to investigate the age of fingerprints by measuring the evolution in time of all of their components at once. To this end, we propose to measure the time evolution of a lumped parameter, the Chemical Oxygen Demand – COD of the fingerprint. This parameter is a measure of the whole composition of the fingerprint.