Determination of Time Since Deposition of Fingerprints via Colorimetric Assays

Lecture Center 3C

Past investigations involving fingerprints revolve heavily around the latent image of the fingerprint – including the minutiae, scarring, and other distinguishing features – in order to visually find a match to its originator. Recently, it has been proven that the biochemical composition of fingerprints can be used to determine originator attributes, such as biological sex, via chemical and enzymatic cascades. While this concept provides pertinent information about the fingerprint originator’s identity, it is not the only piece of information that it can provide. Using ultraviolet-visible (UV-Vis) spectrophotometry, aged fingerprints were evaluated via three previously studied assays used for fingerprint analysis – the ninhydrin assay, the Bradford assay, and the Sakaguchi assay­. As the fingerprints get older, a lower absorbance value is measured. This lowered absorbance is attributed to the fact that fingerprints are composed of biochemical components which decay over time as they are subjected to the conditions of the environment. As a fingerprint ages, the amino acids, proteins, and other biochemical compounds contained in the sweat and sebum decay, affording the ability to estimate the tine since deposition (TSD), or age, of the fingerprint itself.