Identification

Identification means verifying that something or someone is a particular object or person. To a large extent, the field of forensics revolves around this task because, in many cases, laws revolve around the identity of objects or people. The United States legal system includes laws covering topics from voter identification to identity theft to eyewitness identification. Identity must be established before death certificates can be issued and before life insurance policies are redeemed. Forensic scientists may be called upon to identify the origin of objects found at the scene of a crime such as bullets, hairs, or documents. Their work often requires the identification of a person from trace evidence such as fingerprints, blood, or even teeth marks. Forensic scientists maintain a variety of skills and technologies, which aid them in identification.

Each human being has unique characteristics, both physical and social, and these characteristics are what allow for the identification of humans. The study of these characteristics is called biometrics. Biometric techniques attempt to quantify the unique characteristics of a person by measuring them in some way.

The most obvious biometric technique is identification by appearance. This includes a person's height, weight, skin color, hair color, and eye color. Other visible physical markings such as scars, facial hair, and wearing glasses can also be used for identification. Of course, most of these physical characteristics may be altered over time: weight can be gained and lost; hair can be colored; even eye color can change by wearing contacts. Such changes can make features of the appearance deceptive when attempting to identify a person.

Humans have a variety of different physical features that are not obviously apparent that make them unique from one another. These include DNA, the shape of the teeth, hand and fingerprints, and features of the eyes. DNA is an extremely long molecule found in the nucleus of all human cells, including the cells at the root of hairs, and in skin tissue, semen, and blood. DNA is made up of a sequence of four different nucleotides and particular regions of this sequence can vary in unique ways from person to person. These variations can be determined using different biochemical analyses, often called DNA typing or DNA profiling, and are used for identification. Forensic dentistry (odontology) is the study of the various features of teeth that allow for the identification of a person from his or her teeth. Usually identification is based on comparing teeth or bite marks to dental records from an earlier time. Often these comparisons look for the presence of dental treatments and reconstructions. In addition, DNA can be extracted from teeth. Each person's hand and fingerprints are unique, even those of identical twins who have identical DNA. The exact patterning of the ridges, sweat pores, and pores of oil glands has been used for identification in criminal cases since the end of the nineteenth century. Retinal scans rely on the pattern of blood vessels in the back of the human eye, which have a unique pattern in each person. Although somewhat costly, this form of identification is one of the most accurate available.

A third group of biometric features revolve around behaviors that are unique to an individual. These can be social behaviors such as how a person walks or moves, a person's speech patterns and voice inflection, and handicaps that may be apparent. Such features can be documented on video or audiotape and analyzed for identification. Other behaviors used in biometrics include signature analysis, keystroke dynamics, and digitally analyzed voice characteristics.

Finally, physical identifiers can be imposed on people. Examples include branding and tattooing, although these types of identification can be associated with socially repressive systems, such as slavery and racial subjugation. Other forms of imposed physical identification include wearing of jewelry with identifying information such as dog tags, ID bracelets, anklets, and badges. Some of these may even be equipped with radio transponders that not only identify a person, but also his or her location. Microchips have been developed that can be implanted under the skin of valuable breeds of animals so that they cannot be lost and under the skin of endangered species so that information about their migration patterns can be learned. As this technology develops, the application may be applied to the identification of humans in certain circumstances.

The forensic identification of objects spans a broad array of techniques and technology depending on the object in question and the reason for the identification. When fires occur, forensic scientists may be called upon to identify charred remains. In the case of automobile accidents, tire tracks, car parts, and even shards of glass may require identification. Incidents involving guns depend on ballistics experts to identify the bullet as well as the firearm responsible for discharging it. Recovered materials from thefts and forgeries often require the identification of valuables such as artwork, manuscripts, and jewels. Crimes involving breaking and entering require the identification of the tools used to force entry. The examples of investigation related to criminal activity and requiring identification are extensive.