Dactylography: The Scientific Study of Fingerprints
What Are Fingerprints?
Like snowflakes, no two persons' finger prints are exactly alike, not even those of identical twins.
A fingerprint is the pattern on the inside of the finger in the area between the tip and the first joint and stays the same from the day of a person's birth to the day they die.
These two facts make fingerprints very useful in identifying somebody beyond any doubt, and this is why police forces find them invaluable in tracking down a criminal. In more than 100 years of fingerprint record-keeping, no two identical sets have ever been found, even on identical twins. The scientific study of fingerprints, known as dactylography, is used as a technique of crime detection by practically every modern law enforcement agency. Other government agencies and many private businesses also use fingerprints for identification purposes. The largest collection of finger prints is held by the Federal Bureau of Investigation (FBI) in America.
Finger prints are easily classified, as there are four different basic shapes of pattern — arches, loops, whorls, and composites — that are then subdivided according to things like the numbers of ridges between certain points in the pattern.
What Makes Them so Different ?
To begin with, our skin consists of two layers of tissue. One is a thick, deep layer (the "corium") and over it is a delicate membrane called the "epidermis". In cold-blooded animals, the epidermis fits smoothly on the corium. There are no "ridges" to make "prints."
But in mammals, these two layers of the skin are joined very closely. The under layer (the corium) buckles where it meets the upper layer, the epidermis. Some of the tissue of the lower layer projects up into the upper layer moulded over these projections, so that they are firmly and closely attached.
Now, among aome animals, these "pegs" that stick up are scattered at random. There is no pattern of any kind. Among the apes, these pegs are arranged in rows. So the ridges in the upper layer of skin form parallel rows. But since all apes have these parallel rows of ridges, their "fingerprints" are pretty much alike.
But in human beings, the rows of ridges form definite patterns. In fact, the system of classifying human fingerprints was developed by studying these patterns.
Modern governments keep a central file of the fingerprints of all known criminals, in addition to many other classifications of citizens. In the United States, for example, the FBI has a file that includes all present and past members of the armed forces, all federal and state government employees, and many private citizens. In the late 1960's, the FBI files contained the fingerprints of more than 179 million people—or more than four-fifths of the American population.
Fingerprints are recorded by rolling the fingers over a pad stained with printer's ink and making an impression on a standard card. Each finger is printed separately, and an additional print is made of each hand. The card is then forwarded to the FBI, where it is classified according to the number and pattern of the fingertip ridges indicated by the fingerprints on the card. This classification system, known as the Henry system, includes eight basic fingerprint patterns. They are the arch, tented arch, radial loop, ulnar loop, plain whorl, central pocket loop, double loop, and accidental or composite pattern. By a highly ingenious and complex method, each fingerprint card is then filed according to its pattern variation.
When the police investigate a crime, they often check the scene of the crime for fingerprints that may be left invisibly on smooth surfaces by the oil secreted through the fingertips. To discover this latent fingerprint, as it is called, the police dust a fine powder over the surface, making the print visible. Other methods used involve the application of silver nitrate or iodine fumes on the surface. The fingerprints, once visible, are photographed.
If someone is suspected of the crime, the police will take thier fingerprints to see if they match the ones found at the scene of the crime. If they do not match or if the police have no suspect, the photograph of the fingerprints will be forwarded to the FBI in Washington, D.C. There, automatic computers determine the identity of the person to whom the prints belong if they match any of the prints in the FBI file. Within hours the FBI can give local police the name of the person who left the fingerprints at the scene of the crime, as well as other pertinent information about that person. Such information may be used as one of the grounds for arrest and indictment of the suspect. It is also admissible as evidence in the trial of a suspect.
History of Fingerprinting
It has been known for many centuries that each person's fingerprints are different from every other person's. Clay tablets from ancient Babylonia indicate that the first civilizations attempted to identify criminals by their fingerprints. As early as 200 B.C., the Chinese used fingerprints as a personal signature.
Sir William Herschel, a British officer in India in the 1850s, is credited with the first systematic use of fingerprints for identification. The first system that allowed fingerprints to be matched against each other in an efficient manner was devised by Sir Francis Galton, an English scientist, in 1891. His system was later perfected and refined by Sir E. R. Henry, a commissioner of Scotland Yard in London. The Henry system is used in most countries today. Some South American countries, however, use a system devised by Juan Vucetich, an Argentinian.
Fingerprints were first used in the United States in 1903 in New York State prisons. The FBI has maintained its central file since 1924. In recent years, the FBI has cooperated in the International Exchange of Fingerprints, an agreement under which law enforcement agencies of different countries exchange fingerprint data in an effort to control international crime.