chapter  6
4 Pages

Lab 6. The Nature of Latent Fingerprints

Latent fingerprints are invisible fingerprints of unknown origin. They are created when a matrix (composed of sweat and other substances coating the friction ridges) is deposited on a substrate (surface) in the same way a pattern on a rubber stamp is replicated with ink. Pores on the friction ridges excrete eccrine sweat, which originates from eccrine glands deep in the dermis. Eccrine sweat is composed mostly of water, but also contains inorganic and organic compounds including lipids, fatty acids, proteins, and amino acids. When an individual touches his or her face or hair, body oils from sebaceous (lipid-based) sweat also coat the friction ridges. Other contaminants touched during the normal course of a day include lotion, cosmetics, food, soaps, or grease.