Patrick Fritz

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.

A new p-dimethylaminocinnamaldehyde reagent formulation for the photoluminescence detection of latent fingermarks on paper

Dimethylaminocinnamaldehyde was re-evaluated as a wet contact reagent for the treatment of latent fingermarks on porous substrates. A new formulation (consisting of 0.028 g p-dimethylaminocinnamaldehyde, 0.84 mL glacial acetic acid, 6.2 mL ethyl acetate and 0.993 L 40-60 °C petroleum spirits) provides quick, sensitive and robust luminescent ridge detail within 3 h of treatment on both plain and thermal paper. Comparisons to existing formulations indicate improved visualisation and/or a more efficient process.