Amanda Frick

Chemistry of Print Residue

The impressions left by friction ridge skin on the grasping surfaces of the hands not only demonstrate contact, but are also sufficiently discriminating to allow personal identification. They are thus extremely important in criminal investigations to establish links between the objects, victims, and suspects. The most common forms of these impressions are latent (hidden) fingerprints, and successful recovery from a scene or object relies on their detection. A range of physical and chemical methods have been developed over the years for the visualization of latent fingerprints. These methods target differences between the latent fingerprint and the substrate on which it is laid and are based either on physical attraction or a chemical reaction. Knowledge of the chemistry of latent fingerprints is critically important to understanding detection methods. This article provides an overview of the chemical composition of latent fingerprints and a discussion of recent approaches to investigate the factors affecting fingerprint composition.

Investigations into the initial composition of latent fingermark lipids by gas chromatography-mass spectrometry

A more comprehensive understanding of the variability of latent fingermark composition is essential to improving current fingermark detection capabilities in an informed manner. Gas chromatography-mass spectrometry was used to examine the composition of the lipid fraction of latent fingermarks collected from a population of over 100 donors. Variations in the appearances of chromatograms from different donors were apparent in the relative peak sizes of compounds including free fatty acids, squalene, cholesterol and wax esters. Principal component analysis was used as an exploratory tool to explore patterns in this variation, but no correlation to donor traits could be discerned. This study also highlights the practical and inherent difficulties in collecting reproducible samples.