ABSTRACT
There are three types of unintentional friction ridge impressions: patent prints, plastic prints, and latent prints. Patent prints are impressions with a visible matrix, such as blood, paint, or ink. Plastic prints are impressions in a soft substrate such as wax, soap, or clay. Latent prints are unintentional reproductions of friction ridges that are invisible and must be made visible with powders or chemical reagents. Latent prints are composed of eccrine sweat: a mixture of 98% water and 2% organic and inorganic compounds including lipids, fatty acids, proteins, and amino acids. Latent prints are deposited on substrates that vary in porosity, texture, and contour. The exercises in this chapter explore the flow of friction ridge impressions as well as the recognition of minutiae.
