FINGERPRINTS

Fingerprints

Fingerprints

Introduction

Police and scientists have been using fingerprints as a tool for identification since the late nineteenth century, making it the oldest forensic technique still in use. The basic fundamentals in the science of fingerprint identification are permanence and individuality. Fingerprint ridges are formed during the third to fourth month of fetal development and never change in pattern. These ridges have three characteristics—ridge endings, bifurcations, and dots—that appear in combinations that have not been found to repeat in any two people. A ridge ending is simply the end of a ridge. A bifurcation is a Y-shaped split of one ridge into two. A dot is a very short ridge that looks like a spot.

Fingerprints, although often present on hard surfaces, are rarely visible without some enhancement. Latent fingerprint impressions remaining on a surface are composed of trace oils from the contact of the ridges on the person's fingers. To enhance contrast of the latent fingerprint, investigators apply a fine powder, which is trapped by the oil and enables an examiner to view the print. Cyanoacrylate (superglue) fuming is often utilized both to enhance contrast and to affix the fingerprint to the surface. Laser and ultraviolet light sources have also been employed to enhance viewing of fingerprints. Fingerprints should always be photographed prior to lifting with tape or other methods. Fine detail, which is readily visible in a properly shot photograph, may be lost in a tape lift. A positive association in the analysis of fingerprints typically results in an identification of a suspect with scientific certainty.

A searchable database of the fingerprints of convicted offenders (AFIS) has been utilized over the past decade. This has been a tremendous asset to the fingerprint examiner, who previously had to examine fingerprint files by hand when no suspect was provided. This laborious and inefficient process has been supplanted by the AFIS system, resulting in increased production of suspects in cases with no known suspect and the solving of “cold” cases, which would have likely remained unsolved without the AFIS capability.

Discussion

Impressions left by volar skin, or the ridged skin of the palmar surfaces of hands and fingers and plantar surfaces of feet and toes, play a major role in forensic science. Commonly known as fingerprints, palm prints, or footprints, recordings of this skin are often used as a form of physical evidence to link a person to a particular item or location, such as a crime scene. Perspiration, oil, blood, or other substances are often present on the skin and are deposited on surfaces such as plastic, wood, metal, or glass during touches, which might leave a recording of details of the ridge, crease, scar, and imperfection patterns from the skin. The evidence is recovered using a variety of development techniques to make the latent image, or undeveloped print, visible. These include powders, cyanoacrylate glue, chemicals, or stains that adhere to or react with the residues of the print. A variety of different lights and filters can also be used to visualize a latent ...