The thermal visualisation of latent fingermarks on metallic surfaces

Recent published research has lead to improved techniques for recovering latent fingermarks from metallic surfaces. The present study corroborates and extends some of the work carried out by Bond [1], [2] and [3], but an alternative mechanism is proposed for the thermal visualisation of fingermarks based on differential oxidation and the production of interference colours that improve contrast. Fingermarks treated at low temperature could be reheated to enhance recovery, but an upper temperature limit occurs beyond which the mark degrades. The mechanism of enhancement is discussed.