The examination of finger-prints is no easy matter. It is therefore above all necessary that good and true impressions should be taken which can be kept and compared with others.
—Hans Gross
AN ANCIENT BABLYONIAN tablet in the British Museum holds the cuneiform record of an officer’s testimony. In it he tells of being sent by his superior to arrest the defendant, confiscate his property, and take his fingerprints. Because many tablets from this period detail business transactions that were concluded with a fingerprint impressed into wet clay, it is reasonable to assume that 4,500 years ago the Babylonians understood the uniqueness of individual fingerprints.
Some fingerprint fanatics even believe that the seventeenth verse of the Christian apostle Paul’s second letter to the Thessalonians (“The salutation of Paul with mine own hand, which is the token in every epistle: so I write”) is evidence that Paul signed the letter with his fingerprint.
In the third century B.C. a Chinese official pressed his thumb into one side of a clay seal and wrote his name on the other, leading us to the inescapable conclusion that the print’s purpose was one of identification. Thus two thousand years ago someone knew of the immutability of fingerprints. They have shown up in the designs of pottery far older than this. But there is no way to know if these impressions were merely accidents, a design feature, or the potter’s method of signing his work.
The bureaucrats of China’s Tang dynasty (618–907 A.D.) seem to have been aware of the individuality of fingerprints. Kai Kung-yen, an author of the period, writes of the wooden tablets used for contracts centuries earlier, before the invention of rice paper. As he explains, at one time identical notches were cut in the sides of two tablets, each with the contracts written on them. One tablet was then given to each party. “The significance of these notches,” Kai Kung-yen explained, “is the same as that of the finger prints (hua chi) of the present time.”
Bernard Laufer’s History of the Finger-Print System contains an account of the Arab merchant Soleiman. In 851 A.D. he wrote:
The Chinese respect justice in their transactions and in judicial proceedings. When anybody lends a sum of money to another, he writes a bill to this effect. The debtor, on his part, drafts a bill and marks it with two of his fingers united, the middle finger and the index. The two bills are joined together and folded, some characters being written on the spot separating them; then, they are unfolded and the lender receives the bill by which the borrower acknowledges his debt.
In the thirteenth-century Chinese novel Shui hu chuan a husband smears his hand with red ink and presses it onto a divorce document to make it legal. The eighth-century Japanese had a similar practice—there are documents in Japanese archives that bear the handprints of many a long-dead Mikado. The word tegata (hand stamp) survives as a reminder.
A Japanese official presses his fingerprints onto a document, circa 1300 A.D.
A thousand years ago in Tibet, impressions of hands and feet had a religious meaning. As Bernard Laufer explains:
These notions were apparently derived with Buddhism from India. In the Himalayan region of southern Tibet the pious believers are still shown foot imprints left by the famous mystic, ascetic, and poet, Milaraspa (1038–1122). . . . By “traces of snowshoes” is still designated a boulder on which he performed a dance and left the traces of his feet and staff, and the fairies attending on the solitary recluse marked the rocks with their footprints.
In the fourteenth century, Tamerlane (or Timur, as he was known in his own Mongol language) conquered much of what is now Turkey and Iran and founded the brief-lived Timurid Empire. To control his conquered lands, “The officers of the conqueror’s army were appointed to the charge of the different provinces and cities which had been subdued, and on their commissions, instead of a seal, an impression of a red hand was stamped; a Tartar usage, that marked the manner in which the territories had been taken, as well as that in which it was intended they should be governed.”
The Roman barrister and teacher Quintilian, or, as the Romans called him, Marcus Fabius Quintilianus, was the first person we know of to use fingerprints or, more correctly, handprints, as evidence at trial. In about 72 A.D., Quintilian defended a blind teenage boy accused of murdering his father. The evidence? Bloody handprints leading from the father’s bedroom and back along the corridor to the boy’s room. The boy—we do not know his name—had saved his father’s life two years earlier when their house caught fire. In that earlier incident, he had rushed back into the house to save his mother but had been too late. The attempt blinded him.
Did he blame his father for his mother’s death? Had the blame festered and grown as the months passed? Had he, in a moment of unbearable grief, slipped into his father’s room, slid a knife between his father’s ribs, and neatly pierced his heart? Had he then staggered back to his own room, guiding himself down the corridor by putting his hands against the wall, thus leaving a damning trail of bloody handprints? The prosecution, brought by the father’s second wife, the lad’s stepmother, thought so. Unless, they suggested, he had merely murdered his father for his inheritance.
“A nice theory,” Quintilian said, “but it postulates improbable behavior on the part of the boy and impossible behavior on the part of the blood.”
He described how the boy would have had to move swiftly down the hall carrying a knife. The blind boy would do this without bumping into anything, without knowing if a lamp burned or if someone, perhaps a slave, waited somewhere along his path, watching him as he passed. He would then have had to enter his father’s bedroom without being able to see if his father or stepmother were awake; he would have approached the bed without stumbling and then thrust a knife faultlessly between his father’s third and fourth ribs and into his heart. Then the lad would have soaked his hands in his father’s blood before stumbling back to his own room, where he was found sleeping, innocent of bloodstains, the next morning.
And the handprints? Didn’t a clear line of bloody impressions along the corridor leading from the death chamber to the lad’s bedroom prove the lad’s guilt?
“Nonsense,” said Quintilian. Just the opposite. They were proof the boy was innocent.
“Blood,” he told the jury, “does not behave that way. Surely you veterans of the legions of Rome should understand the ways of shed blood. All the bloody handprints were even and clear. If the boy had indeed staggered down the hall, resting his blood-soaked hand against the wall as he went, the prints would have become fainter and fainter as he went. To achieve a row of clear prints, someone had to keep his or her hand wet with blood by dipping it again and again in the corpse’s wound. Someone who wanted to blame the boy. Someone who had eyes to see where to insert the knife blade. Someone who would inherit a fortune if, and only if, the boy were convicted of patricide.”
The boy was found innocent. According to the record, the stepmother subsequently confessed.
The world waited almost two millennia before fingerprints, or, as the British police called them, “dabs,” would figure again in a murder trial. Two facts had to be established before fingerprints could be used for positive identification: that they are unique—that no two people, even identical twins, have the same fingerprints; and that a person carries the fingerprints he is born with unchanged throughout his life. To make fingerprints truly useful, it was also necessary to devise a way to locate a specific fingerprint out of the myriad in the file.
In 1684, Nehemiah Grew, an English doctor and a fellow of the Royal Society, published a lecture in which he commented on the ridge patterns on fingertips. If it occurred to him that these could be used for identification purposes, he did not mention it.
Two years later, Marcello Malpighi (1628–1694), a professor of anatomy at the University of Bologna who gave his name to the Malpighi layer, one of the subdivisions of human skin, published De Externo Tactus Organo (Concerning the External Organs of Feeling). In it he described the ridged pattern of the skin of the fingers and palm. Again, he did not suggest that anything useful could be done with the information.
In 1818 the artist and engraver Thomas Bewick (1753–1828) published an edition of Aesop’s Fables which he illustrated with his own woodcuts. On the title page he placed a woodcut of one of his own fingerprints over the legend, “Thomas Bewick—his mark.” We can assume that Bewick was at least artistically aware of the uniqueness of fingerprints.
Johannes Evangelist Purkinje (1787–1869), a professor of anatomy and physiology at Breslau University, was the first person to attempt to examine fingerprints and classify them by type. His name is associated with many medical discoveries—Purkinje’s cells, fibers, networks, vesicles, and more. In a thesis written in 1823 for his doctor of medicine degree at the University of Breslau, he divided fingerprints into nine groupings. As he said in the thesis: “After numerous observations, I have thus far met with nine principal varieties of curvature according to which tactile furrows, or furrows susceptible to touch, are disposed upon the inner surface of the last phalanx of the fingers.”
In 1858, William James Herschel, then employed by the East India Company in Bengal, India, was in Jungipur on the upper reaches of the Hooghly River. He was in the process of drawing up a contract for road-building materials with a supplier named Rajyadhar Konai, a man who was known to take such agreements lightly. In order to impress upon him the importance of the contract, Herschel had Konai place his handprint on the reverse of the document. Two years later Herschel, then a magistrate at Nuddea, near Calcutta, was charged with seeing that the many natives who were destitute in the aftermath of the Great Mutiny received their government pensions. As most of the natives could neither read nor write and thus could not sign anything, the possibilities for fraud were endless. The criminal element was quick to exploit these possibilities.
Although he had taken Konai’s handprint as a talisman of the seriousness of keeping one’s word, Herschel realized that fingerprints could also serve as a positive means of identification. Once he began placing the pensioners’ thumbprints on their receipts, the number of fraudulent claims fell dramatically.
For the next two decades, Herschel continued his study of fingerprints. He became convinced that they did not change with age, and that no two were alike. In 1877, in a letter to the inspector general of the prison system of Bengal, he outlined his researches: “I have taken thousands [of fingerprints] now in the course of the last twenty years, and I am prepared to answer for the identity of every person whose sign manual I can now produce if I am confronted with him.” But the inspector general refused Herschel permission to try out his system, even on a small scale in a local prison. Disillusioned and in poor health, Herschel returned to England in 1879.
While Herschel experimented in India, Dr. Henry Faulds (1843–1930), a Scot who served as a resident physician at the Tsukiji Hospital in Tokyo, became fascinated with fingerprints. His interest began when he noted the impressions of potters’ fingers on specimens of prehistoric Japanese pottery. He began a systematic study of fingerprints, determining that each of the prints he collected was unique and that an individual’s prints did not change over the course of a lifetime. He found that the best medium for transferring the prints was a thin film of printer’s ink on which the finger was rolled before being rolled again onto a card—a method still in general use today. In 1879, Faulds was able to use his developing science to aid the local police, thus becoming the first person to solve a crime with fingerprint evidence.
While inquiring into a burglary near Faulds’s home, police investigators noticed some grimy fingerprints on a wall of the house. Knowing of Faulds’s fascination with fingerprints, they invited him to examine the marks. At about the same time they also arrested a suspect. Faulds took the suspect’s fingerprints and, after comparing them to the marks on the wall, declared him to be innocent. When a second suspect was apprehended a few days later, Faulds found that his prints matched the ones on the wall. A short while later Faulds helped the police again by lifting the fingerprints from a mug and comparing them with those of the suspect. They matched, and another burglar was caught.
A year later, on October 28, 1880, a letter from Faulds appeared in the British journal Nature. In it he outlined his discoveries and proposed the establishment of a scientific method of fingerprint identification. He also discussed his own experience in using fingerprints to solve crimes, saying in part, “When bloody fingermarks or impressions on clay, glass, etc., exist, they may lead to the scientific identification of criminals.”
A reply from Herschel, in which he related his own experience in India, appeared in the next issue of Nature. Thus began a feud between the two men over who could claim priority in the use of fingerprints for identification.
In 1882 in the New Mexico Territory of the United States, a government geologist named Gilbert Thompson began using his own thumbprint on pay orders and requisitions in an effort to prevent forgeries. Where he came up with the idea is not known. A year later Mark Twain published Life on the Mississippi, a memoir in which he recalls the solution of a crime by the use of fingerprints. “When I was a youth,” Twain wrote,
I knew an old Frenchman who had been a prison keeper for thirty years, and he told me that there was one thing about a person which never changed, from the cradle to the grave—the lines in the ball of the thumb; and he said that these lines were never exactly alike in the thumbs of any two human beings. In these days, we photograph the new criminal, and hang his picture in the Rogues’ Gallery for future reference; but that Frenchman, in his day, used to take a print of the ball of a new prisoner’s thumb and put that away for future reference. He always said that pictures were no good—“The thumb’s the only sure thing,” said he; “you can’t disguise that.” And he used to prove his theory, too, on my friends and acquaintances; it always succeeded.
We don’t know if Mark Twain considered the story fact or fiction, but his old Frenchman had his facts right. He knew as much about fingerprinting as any man of his day and more than most. Twain’s story is illustrated with woodcuts of fingerprints, whether Twain’s or the artist’s we do not know.
Twain’s fascination with fingerprints continued. Ten years later a major plot point in his book Pudd’nhead Wilson revolved around a courtroom identification based on fingerprint evidence.
In 1886, Faulds, then back in Britain, offered to set up a fingerprint bureau for Scotland Yard at his own expense. His offer was rejected. The authorities realized that neither Herschel nor Faulds had developed a classification method that allowed for later retrieval. Without such a method, the value of fingerprints for identification was extremely limited.
Enter the noted British scientist Sir Francis Galton (1822–1911). In the 1880s he became interested in dactyloscopy, as the study of fingerprints had become known. Galton, a cousin of Charles Darwin, was a medical doctor as well as a geneticist and anthropologist. At the age of twenty-three he had led an expedition to the Sudan and southwest Africa; he later wrote Meteorographica (1863), a meteorological treatise in which he presented the modern method of weather mapping. He was sixty when his interest in anthropometry led him to the application of statistical methods in anthropology and heredity, an endeavor that resulted in the founding of the study of eugenics.
Sir Francis had for many years conducted statistical studies of human hereditary traits, an effort that gave him a working familiarity with anthropometric measurements. As a result of his study of inherited characteristics, he became proficient in Bertillon’s system of body measurement. His work soon made him a recognized expert.
In 1888, Galton was asked to deliver a lecture on Bertillonage to the Royal Institution of Great Britain. In preparing his lecture, he focused on the problems of individual identification and became fascinated with the possibilities he saw in the use of fingerprints. As he later related in his book Finger Prints: “Wishing to treat the subject generally, and having a vague knowledge of the value sometimes assigned to finger marks, I made inquiries and was surprised to find how much had been done, and how much there remained to do before establishing their theoretical value and practical utility!”
Herschel kindly lent Galton his collection of fingerprint cards, and Galton spent the next three years establishing that fingerprints remained unchanged throughout a person’s life and that it was theoretically possible to devise a method of classifying them. Using an extremely conservative estimate of the degree of variability in a given fingerprint, Galton calculated the probability of two sets of prints matching to be i in 64 million. (The figure given today is much larger.) (Some popular articles on fingerprinting have claimed that identical twins have identical fingerprints. This is not so. In some cases the prints will correspond in primary and secondary classifications, which means that their cards will be filed in the same general area of the record section, but direct comparison of the two sets of prints will show that they are quite different.)
In Finger Prints, Galton declared that he had found fingerprints to be permanent and immutable:
As there is no sign, except in one case, of change during any of these four intervals which together almost wholly cover the ordinary life of man (boyhood, early manhood, middle age, extreme old age), we are justified in inferring that between birth and death there is absolutely no change in, say, 699 out of 700 of the numerous characteristics of the markings of the fingers of the same person such as can be impressed by him wherever it is desirable to do so. Neither can there be any change after death up to the time when the skin perishes through decomposition: for example, the marks on the fingers of many Egyptian mummies and on the paws of monkeys still remain legible. Very good evidence and careful inquiry is thus seen to justify the popular idea of the persistence of finger markings. There appear to be no bodily characteristics other than deep scars and tattoo marks comparable in their persistence to these markings; at the same time they are out of all proportion more numerous than any other measurable features. The dimensions of the limbs and body alter in the course of growth and decay; the color, quantity, and quality of the hair, the tint and quality of the skin, the number and set of the teeth, the expression of the features, the gestures, the handwriting, even the eye color, change after many years. There seems no persistence in the visible parts of the body except in these minute and hitherto disregarded ridges.
Galton developed a tentative approach to the problem of indexing fingerprints, an approach based upon whether the predominant pattern of each individual print was an arch, a loop, or a whorl. In 1893 the British Home Office established a committee headed by Charles Edward Troup to recommend a criminal identification system for use by Scotland Yard. The Troup Committee consulted with Galton and were impressed with the potential of the fingerprint identification method that he demonstrated in his laboratory. But Galton, the true scientist, explained to them that his system was too complex and unwieldy for use outside the laboratory. It would be some years, he said, before a reliable system could be perfected.
The Troup Committee therefore recommended that Bertillon’s anthropometric system be adopted by Scotland Yard, but that it be supplemented by fingerprinting. This way, a library of fingerprints would be available when a comparative method was perfected. And this suggestion was approved.
In 1894, Galton, who was then seventy-two, passed the torch of dactyloscopy to Edward Henry (1850–1931). It was Henry who carried it to success.
The London-born son of a doctor, Edward Henry was a career civil servant who rose to the post of inspector general of police for the province of Bengal. While in India he had read Galton’s Finger Prints and subsequently traveled to England especially to meet him. Galton, with his usual generosity, talked to Henry for hours and explained the problems of classification he had solved and those that remained. He loaded Henry down with as many fingerprint cards and pages of notes and examples as he could carry and sent him away.
Back in India, Henry worked on the problem for the next two years. He settled on five basic patterns for fingerprints: arches, tented arches, radial loops (slanting toward the thumb), ulnar loops (slanting away from the thumb), and whorls. He designated these by the letters A, T, R, U, and W. He analyzed them further by showing that a straight line that connected two specific locations on a print could be drawn and the number of ridges cut by that line then counted. These letters and numbers would produce a specific code for any fingerprint card that held the prints of all ten fingers. Any two investigators categorizing the same fingerprint card would come up with the same code.
The system was complex and required intensive effort to master, but it worked. Once it was in use, no felon could hope to hide his previous record or outstanding arrest warrants from the police.
In July 1897, after a one-year trial, the Indian government officially replaced Bertillonage with dactyloscopy. In 1901, Henry was called back to London to head Scotland Yard’s Criminal Investigation Division (CID). As the assistant commissioner of police, he oversaw the discarding of anthropometry and the adoption of his own system of fingerprinting as the sole means of criminal identification. It quickly proved its usefulness, transforming the process of identifying criminals from a time-consuming task fraught with the possibility of error into a routine procedure that was as close to infallible as anything yet devised. If two fingerprint cards held matching prints, they had been made by the same person, and no question about it.
As Henry perfected his system, an Argentine detective was independently developing a fingerprint system of his own. Austrian-born Juan Vucetich (1858–1925) emigrated to Argentina at the age of twenty-six. Shortly after arriving, he joined the La Plata police department, where within five years he became head of the statistical bureau. In 1891 he set up an office of anthropometry for the identification bureau of the central police department in La Plata. As he worked with anthropometry, Vucetich became aware of its shortcomings and began to look for a better system. After reading an article on Galton’s research in the May 1891 issue of Revue Scientifique, a French science magazine, Vucetich worked out his own system of four primary categories of fingerprints.
In 1892, while Vucetich was developing his system, a woman named Francesca Rojas, who lived in Moecochea, in the province of Buenos Aires, was found in her home in serious condition with stab wounds to her neck. Her two sons lay dead, both with their throats cut. Rojas accused a former lover who lived nearby of committing the crimes. The police, at the request of their superiors in La Plata, cut a bloodstained section of wood from the doorjamb and forwarded it to the identification bureau. There, a fingerprint was found in the bloodstain that proved to be that of Rojas herself. She confessed to the crime and went to prison.
Convinced of its value, for years Vucetich financed the development of fingerprint classification from his own meager salary. The authorities refused to consider switching from Bertillonage even when in one day Vucetich identified twenty-three criminals who had successfully fooled the Bertillon system. Finally, under a new police chief, in 1894 Argentina adopted the Vucetich system of classification. In 1896 Bertillonage was officially dropped.
In what may be a supreme irony, when Vucetich went to Paris a few years later and met Bertillon, the Frenchman accused him of using Bertillonage without permission or proper credit. Bertillon physically attacked him. What might Bertillon have done had he known that Vucetich had abandoned anthropometry for dactyloscopy?
In 1904, Vucetich explained his system in his book Dactyloscopia Comparada. In 1907 the French Académie des Sciences judged it the best of all they examined, and by 1912 it was in use by all the countries of South America.
Meanwhile Great Britain and most of the countries of Europe used the Galton-Henry system. France, Belgium, and Egypt used an amalgam of the two systems, with France also retaining anthropometry for the first half of the twentieth century. Even Bertillon had by this time incorporated fingerprints into Bertillonage. Curiously, in 1902, during the first criminal prosecution in France based on fingerprint evidence, it was Bertillon who made the identification. A man named Joseph Reibel had been strangled in a dentist’s office on the Rue du Faubourg Sainte Honoré in Paris, and a single bloody fingerprint had been left on a glass shard at the scene. Bertillon photographed the print, and, through intensive searching (at that time he had to methodically examine every card), he matched it to that of an ex-convict named Scheffer. Several eyewitnesses were also able to identify Scheffer from his photograph. When he was eventually apprehended in Marseille, he confessed.
In the United States the practice of fingerprinting and of maintaining fingerprint files began in the major penitentiaries. Sing Sing began using the Henry system in March 1903, and other New York state prisons took it up shortly thereafter. The federal penitentiary in Leavenworth, Kansas, switched from anthropometry to fingerprinting toward the end of 1904. Officials there were readily convinced because of an incident that had occurred there the year before. In 1903, as a new prisoner named Will West was being measured for his Bertillon record, Warden R. W. McClaughty asked why the man’s record was being duplicated. West protested that he had never before been at Leavenworth or any other prison. The warden pulled the record of one William West, convict number 2626, from the files, and confirmed that it corresponded to the prisoner’s Bertillon measurements. And the photograph looked just like him. When Will West persisted in his denials, the warden checked further and found that the William West of record 2626 was already a prisoner. The two men shared variants of the same name, looked the same down to the smallest detail, and shared identical Bertillon measurements. McClaughty had the prints of their left index fingers taken and compared, and was relieved to discover that in fact the two Wests were entirely different men.
The Bertillon measurements of William West, dated 9 September 1901, were: 19.7, 15.8, 12.3, 28.2, 50.2, 1.78.5, 9.7, 91.3, 1.87.0, 6.6, 14.8.
The new Will West card read: 19.8, 15.9, 12.2, 27.5, 50.3, 1.77.5, 9.6, 91.3, 1.88.0, 6.6, 14.8. All the corresponding numbers were either identical or well within the permissible variance.
One of the major advantages of fingerprint identification is the ease of record-taking. Other unique features of human physiognomy have been suggested as possible bases for identification systems: the pattern of the retina, the pores of the tongue, brain waves, voice prints, and even nose prints. When fingerprints have been unavailable or impossible to obtain, forensic dentistry has proved invaluable in identifying corpses. DNA typing is now possible when a suspect has left blood, sera, or tissue at the scene of the crime. But fingerprints still provide the most practical and most certain means of identification.
In 1924 the U.S. Congress authorized the Bureau of Investigation in the Justice Department (now the Federal Bureau of Investigation) to create and maintain the Identification Division. The FBI combined the fingerprint files maintained at Leavenworth with the large collection kept by the International Association for Chiefs of Police. Thus the Identification Division began its existence with a collection of 810,188 prints.
On July 1, 1931, the federal government made it mandatory for anyone applying for one of forty thousand civil service jobs to be fingerprinted. The prints would be compared against the FBI’s master file, which at the time held about two million cards. The collection grew rapidly—eleven years later, on May 24, 1935, the Identification Division filed its five millionth card.
According to FBI records, the Identification Division’s ten millionth card, received on January 31, 1946, was that of child actress Margaret O’Brien, taken when the nine-year-old star was touring FBI headquarters in Washington, D.C. As of February 1, 1991, the FBI had a total of 193,137,999 prints in its files, of which 107,058,738 were in the criminal division.
Today, a century after Galton, Henry, and Vucetich, along with their imitators, adapters, combiners, improvers, simplifiers, and translators, the field of dactyloscopy is undergoing dramatic change. The computer has brought a degree of speed and accuracy to fingerprint analysis that could never be hoped for before. The FBI began testing computers in its Identification Division in 1972, and by 1980 it began computerizing the entire criminal fingerprint file. On June 5,1989, computer processing of fingerprint cards went on line, and response time for the average request was immediately cut from two weeks to one day.
Here is a brief overview of the art and science of fingerprint classification, both historical and technical. Feel free to skip over the technical parts if you are not planning to classify any cards in the near future.
The intellectual basis for using fingerprints for identification rests upon three premises:
1. Fingerprints are unique. For one finger alone, the number of possible patterns is in the hundreds of billions. This reliance on uniqueness is supported by the empirical fact that of the millions of fingerprints on record, no two have ever been found to be the same. Even identical twins with identical DNA have different fingerprints.
2. Fingerprints do not change. The prints of a small child will be recognizably the same in old age, allowing, of course, for the growth of the finger from childhood to adulthood and for any scars that may be acquired along the way.
3. A fingerprint will fall into one of several recognizable categories. This allows fingerprints to be classified according to an invariant system and permits one fingerprint to be found among the millions on file.
The method for taking fingerprints devised by the early fingerprinters is pretty much still in use today, though it is being superseded by more technical means. We will look at these further on. In the traditional method, printer’s ink is spread evenly on a glass plate with a rubber roller; the person to be fingerprinted then rolls his fingers one at a time on the plate and then onto a fingerprint card that is usually in some sort of holder. After the individual fingerprints are taken, each hand is inked as a whole and pressed onto the card. The full handprint, called a flat print, is taken as a means of checking that each individual print is indeed from the finger indicated by its position on the card.
Printer’s ink or something similar is used because it dries quickly and because when applied to the finger it adheres only to the ridges and does not flow into the creases. Thus a clear impression is made. Stamp-pad inks, which have been used when nothing better is available, tend to give blurred impressions. There are also various fluids for taking prints. These leave the fingers clean and develop an image on the card, but they tend to be expensive and more difficult to use.
The standard fingerprint record card, in use throughout the world, is an eight-inch square of medium-weight cardboard. It was devised in 1908 by P. A. Flak, a fingerprint expert at the Library Bureau Company of Chicago, who designed the card to be easy to file and retrieve. The actual information provided at the top of the card varies from place to place and according to whether the card is to be used for criminal identification, a military record, or civilian use (for a job application, for instance). In any case, whatever the category or the recording agency, if the print is taken in the United States a copy will probably be sent to the FBI and filed in the appropriate national registry. And while Flak’s card is still in use throughout the world, more and more police departments are turning to photographic or electronic means of taking prints.
The systems devised by Henry and Vucetich for locating one card out of the millions in the files form the basis for everything that followed. Dactyloscopy now recognizes five basic patterns within fingerprints: arches, tented arches, radial loops (slanting toward the thumb), ulnar loops (slanting away from the thumb), whorls, and, finally, accidentals—traits that do not fit within the first five categories. The FBI’s classification system further divides the loop into the double loop and the central pocket loop. Experience has shown that the loop pattern is the most common, making up more than 65 percent of the whole. Whorls make up about 30 percent, and arches and tented arches the remaining 5 percent. The accidentals account for fewer than 1 percent. The actual percentages vary from country to country. The pattern of the fingerprint is formed by the raised ridges that apply the ink to the card, or that leave the grease or sweat on the window pane or the household object.
Arches have a moundlike contour, with ridges that run from one side of the print to the other. Tented arches come to a point or spike. Usually a few extra arches curve over the spike.
Whorls are circular or spiral and form a complete oval around a central point.
Loops are more strongly curved than arches, with ends that enter and leave the print from the same side of the finger. Radial loops slant toward the thumb, and ulnar loops slant away from the thumb.
Of course, like most things in nature, it is never that simple. The ridge-lines of fingerprints occur in randomly curved patterns that probably evolved in order to create a skin surface that made it easier to grasp things. Nature was hardly thinking about the uniformity of pattern design. Whereas some fingerprints clearly form whorls, loops, or arches, many resemble a whorly arch, or an arched loop. The books on fingerprint classification devote many pages to demonstrating why this is a whorl while that is certainly a loop. And in order to make the classification system work, it is necessary that every fingerprint examiner see every fingerprint in the same way as every other member of the clan.
Rules had to be drawn up for the exceptions and rarities. Because the classification system is based on all ten fingers, what do you put down if one finger is missing? (It is given the same classification as that of the corresponding finger on the other hand.) What if a finger is so badly scarred as to have no usable print? It still has some pattern that can be recorded; and, if it is that badly scarred, it may well be unusable as a finger. And what if a hand has six fingers? Which one do you eliminate?
The Henry system and its cousin, the Vucetich system, as modified over the years, are the fingerprint classification systems in use over most of the world. To use them requires training in a process that is neither self-evident nor simple. As Peter Laurie says in his book Scotland Yard, “To the layman, Henry’s system appears to be one of the most obscure inventions of the human mind.” Still, any two people properly trained in the system will come up with the same classification for the same fingerprint card.
The basics of the system are easy to understand. What makes them forbidding to the layman is their somewhat arcane logic and their resemblance to mathematics.
In the Henry system, primary classification is based on the number and location of whorls among the prints. The fingers are numbered consecutively from the right thumb to the left little finger, and a numeric value given to each whorl, as follows:
RIGHT HAND
If the pattern on any finger is not a whorl, its value is o. Now comes the fun part. First we make a fraction by adding the value of every print: even-numbered fingers are added together to create the numerator (the top number of the fraction), and odd-numbered fingers are added together to make up the denominator (the bottom number). A fingerprint card on which none of the fingers is a whorl would be classified 0/0. But that does not look right somehow, and it was decided that a 1 be added to both the upper and lower numbers of the fraction. That way the smallest fraction obtainable became 1/1 and the largest became 32/32. Note that this is not really a mathematical process—mathematically 32/32 is identical to 1/1 because both equal 1. In this case, if you simplify your fractions, you’ll lose your data.
This process produces a total of 1,024 possible fractions that divide the collecting agency’s indigestible collection of fingerprint cards into 1,024 separate files. If the collection were made up of, say, a half-million cards, each file would hold about 500 cards. This number would take a while to go through but would not be altogether unmanageable. On the other hand, when the collections grow to millions of cards, further winnowing classifications are needed.
Fingerprints can now be taken electronically or optically. These methods, combined with rapid computer recognition, mean that your finger can be used for instant identification at ATM machines or for entry to secure areas. And to further reassure those with a macabre sense of insecurity, the machines can distinguish between a living finger and a dead one. So cutting off someone’s finger will not enable criminals to access their ATM accounts.
AFIS is the generic name for any automated fingerprint identification system. Today all AFIS systems are computer-generated, using sometimes different logarithms to achieve the same results. While several states have set up their own AFIS systems, the U.S. Integrated Automated Fingerprint Identification System, run by the FBI, holds all the fingerprint sets collected in the United States. AFIS systems are very useful when two fingerprint cards are being matched, as when someone applies for a job and her fingerprints are submitted for a security check. If she has ever been printed before, a match between the two cards will almost certainly be found. By instantly narrowing the selection down to about fifty, the AFIS system can save a lot of time in the search for a single print. Still, when seeking a match for an imperfect latent print lifted from a crime scene, the expertise and judgment of a trained fingerprint examiner are essential.
