The Nature of Latent Prints
Latent prints are chance impressions left by the contact of friction ridges with a substrate. The print is composed mainly of eccrine sweat secreted by pores along the friction ridges. Eccrine sweat is 98% water and 2% other organic and inorganic compounds. Patent prints are chance impressions left in a visible matrix such as blood, paint, or ink. Plastic prints are three-dimensional chance impressions in a tacky substrate such as clay, soap, or glue. Latent, patent, and plastic prints are subject to distortion since they are deposited on a substrate by chance. Distortion occurs due to movement, the elasticity of friction ridge skin, and the condition and texture of the substrate. It is not currently possible to determine how long a latent print has persisted on a surface. Touch DNA has become an increasingly prevalent analysis. It is thus critical to be cognizant of the potential for contamination when processing latent prints.