Forensic sciences : fingerprint techniques

Physical evidence at a crime scene may be present in an infinite variety of forms and materials. Some of the trace materials and marks left by the offender may be of limited evidential value, while others may be of significant benefit to the investigation. Several forms of evidence can permit the identification of an individual (e.g., fingermarks, dental structure, and genetic code), but the patterns formed by the friction ridges of the fingers and palms are arguably the most useful and general proof of identity. These patterns are unique, immutable, universal, easy to classify, and leave marks on any smooth object handled with the bare hands. Smooth objects that have been touched with the bare hands will retain latent impressions, composed of natural secretions and contaminants, of the corresponding ridge patterns on the fingers and palms. In criminal investigations, the detection and recording of a fingermark on a particular item can serve as proof that the item was touched by a specific person. It is for this reason that physical and chemical techniques, capable of developing latent fingermarks on a wide variety of surfaces, are essential tools for the criminalist. Considerable research into these techniques has been conducted over the last 25 years, and this has led to a dramatic improvement in the sensitivity of fingerprint detection. Latent fingermarks that would once go undetected can now be exploited using routine processing methods.