Fingerprints are the oldest and most accurate method of identifying individuals. No two people (not even identical twins) have the same fingerprints, and it is extremely easy for even the most accomplished criminals to leave incriminating fingerprints at the scene of a crime.
Each fingerprint has a unique set of ridges and points that can be seen and identified by trained experts. If two fingerprints are compared and one has a point not seen on the other, those fingerprints are considered different. If there are only mathing points and no differences, the fingerprints can be deemed identical. (There is no set number of points required, but the more points, the stronger the identification. Fingerprints can be visible or latent; latent fingerprints can often be seen with special ultraviolet lights, although on some surfaces a simple flashlight will identify the print. Experts use fingerprint powder or chemicals to set a print; they then “lift” the print using special adhesives.
The use of fingerprints for identification goes back to ancient times. In ancient Babylonia and China, thumbprints and fingerprints were used on clay tablets and seals as signatures. The idea that fingerprints might be unique to individuals dates from the fourteenth century. In 1686 the physiologist Marcello Malpighi examined fingerprints under a microscope and noted a series of ridges and loops. In 1823, another physiologist, Jan Purkinje, noted at least nine different fingerprint patterns.
The pioneer in fingerprint identification was Sir Francis Galton, an anthropologist by training, who was the first to show scientifically how fingerprints could be used to identify individuals. Beginning in the 1880s, Galton (a cousin of Charles Darwin) studied fingerprints to seek out hereditary traits. He determined through his studies not only that no two fingerprints are exactly alike, but also that fingerprints remain constant throughout an individual’s lifetime. Galton published a book on his findings in 1892 in which he listed the three most common fingerprint types: loop, whorl, and arch. These classifications are still used today.
It did not take long for law enforcement officials to recognize the potential value of fingerprint evidence. Sir Edward Richard Henry, a British official stationed in India, began to develop a system of fingerprint identification for Indian criminals. (Henry created 1,024 primary fingerprint classifications.) In Argentina, Juan Vucetich, a police official, also used Galton’s findings to create a fingerprint system. (He used Galton’s research to make a fingerprint identification of a murderer in 1892.) By the beginning of the twentieth century, Scotland Yard had begun to compile fingerprint information, using a classification system based on Henry’s work and creating a Central Fingerprint Bureau. In the United States, the New York Police Department, the New York State Prison System, and the Federal Bureau of Prisons instituted a fingerprint system in 1903, and in 1905 the U.S. Army began using fingerprint identification.
The first murder case in the United States in which fingerprint evidence was used successfully was in Illinois in 1910, when Thomas Jennings was accused of murdering Clarence Hiller after his fingerprints were found at Hiller’s house. Jennings appealed his conviction, but the Supreme Court of Illinois upheld the evidence in 1911 and Jennings was executed in February 1912. People v. Jennings thus established fingerprint evidence as a reliable standard.
The Federal Bureau of Investigation (FBI) established a fingerprint repository through its Identification Division beginning in 1924. This repository held fingerprint cards in a central location. Over the next 50 years the FBI processed more than 200 million fingerprint cards. To eliminate duplicate fingerprints and make it easier to store and share fingerprints among law enforcement agencies, the FBI developed the Automated Fingerprint Identification System (AFIS) in 1991, which computerized the card system. The Integrated AFIS system (IAFIS) was introduced in 1999; a law enforcement official can request a set of criminal prints from IAFIS and get a response within two hours.
Fingerprints are kept for criminals, but civil fingerprints are also kept. People who apply for government jobs, jobs that handle confidential information, banking jobs, teaching jobs, law enforcement jobs, and any job that involves security issues can be fingerprinted. IAFIS stores civil prints as well as criminal prints.