Fingerprinting is a method of identifying people using impressions made by the fingers, thumb, and palm of the hand. These impressions show patterns formed by small ridges on the skin. Each person has a unique pattern of ridges. Experts believe that no two people have identical fingerprints. Fingerprints generally remain the same throughout a person’s life. They only change in cases of certain diseases or injuries.
Law enforcement officers use fingerprints to investigate crime. Expert witnesses often present fingerprints as evidence in criminal trials. Prints may also help identify victims of wars, natural disasters, epidemics, accidents, and other circumstances that make other identification methods impossible. Some government agencies and corporations use fingerprinting to prevent crime. For example, many airports, banks, and military bases check fingerprints before allowing access to certain areas and computer systems.
Today, organizations and individuals increasingly identify people through examination of genetic (hereditary) material. This is called DNA analysis or DNA fingerprinting. DNA identification is a more scientifically advanced process. But it is not always as specific. For example, identical twins have identical DNA but different fingerprints. See DNA fingerprinting.
Types of fingerprints.
There are four main types of fingerprints. They are (1) known prints (also called exemplar prints); (2) latent prints; (3) patent prints; and (4) plastic prints. Known prints are intentionally recorded from a person for the purpose of identification. Traditionally, known prints are recorded by applying ink to a person’s fingers. The fingers are then pressed or rolled onto paper. Today, many known fingerprints are recorded electronically and stored in computer databases. Investigators may collect latent prints from a crime scene. The prints do not become visible until exposed by some method. Patent prints are prints easily visible to the unaided eye. Plastic prints are three-dimensional impressions in a soft or flexible surface, such as wax.
Most latent fingerprints are formed by residue of perspiration and oils from human skin and other substances picked up from the environment. These prints must be developed (made visible) to be photographed. Development methods vary depending on the type of surface being examined. Examiners may use powders or chemicals to make latent prints visible. These substances stick to the invisible residues, making the fingerprint visible. Some fingerprints are clearly visible and do not need to be developed. These often include fingerprints made by soiled fingers. They may also include those found on such surfaces as dust, blood, or powder.
Fingerprint identification.
Trained fingerprint examiners compare collected fingerprints with known standards to determine if they came from the same person. Many countries require that prints have a certain number of matched characteristics. These are points where ridges in the skin end or branch. In other countries, however, the examiner decides independently whether the prints have enough detail for an identification.
People often use computers to aid in fingerprint identification. Computers can sort through huge fingerprint databases, producing lists of possible matches to a collected print. A trained examiner then decides whether two prints share enough unique characteristics for a positive identification.
There are two main purposes for taking and examining fingerprints. They are archival fingerprint identification and forensic fingerprint identification. In archival fingerprint identification, examiners compare new known prints with known fingerprints collected earlier. Archival fingerprint identification is often used to verify or disprove claims of identity. Security officials often use archival fingerprint identification to check people’s identity during international travel. During this process, they may compare a person’s fingerprints with an electronic database of known criminals or terrorists.
In forensic fingerprint identification, examiners compare latent fingerprints with known prints collected from suspects or victims. The main goal is to help identify or eliminate suspects in a criminal investigation. However, latent fingerprints are often distorted or incomplete. As a result, they may appear different from known prints, even if they are from the same person. Forensic examiners disagree over the exact number and types of similarities needed for an accurate identification.
History.
In the 1860’s, Sir William J. Herschel, a British colonial administrator, began using archival fingerprint identification to prevent fraud in India. In 1880, Henry Faulds, a Scottish doctor, proposed the use of forensic fingerprint identification to help solve crimes. During the 1880’s and 1890’s, Francis Galton, a British scientist and statistician, worked to develop the scientific foundations for fingerprint identification.
See also Biometrics; Footprinting.
