FINGERPRINTS: The Longest Running Biometrics Success Story

Even though the use of fingerprints is more than a century old, no better method of proving personal identification has yet been devised, and fingerprinting continues to be a vital weapon in the arsenal of police forces worldwide, both as a means of maintaining accurate criminal records and detecting crime. AFIS technology is now starting to be used not only in police, border protection and counter-terrorist applications, but also in a host of other security areas where personal identification is needed. These areas include passports, ID cards, physical access control, time and attendance systems, and other applications.

By Ming Hsieh

We are not all the same.  Each man, woman and child is an individual and can be picked out from the several billions of other human beings spread across the globe.  When we recognize someone, we do it very quickly, mostly subconsciously, and though it may seem a very trivial exercise, it is actually one of the most complex computational procedures known.

If we ask a machine to do the recognizing, the operation is called ‘biometrics’ -- the technology concerned with automated methods of recognizing a person based on physiological or behavioral characteristics.  Physiological features are what a person ‘is’ in other words, entities that form a part of a person’s physical makeup.  Examples, going roughly from head to toe, include hair chemistry, the shape of the face, patterns of iris and retina, ear prints, teeth, voice properties, wrist veins, hand geometry, foot impressions, DNA, and even body odor.  Behavioral characteristics are what a person ‘does’ and they include handwriting and signatures, the manner of walking, and speech patterns.

In our own private lives, we obviously need the sixth sense of person recognition, which has evolved over millions of years, so that we can form and maintain relationships.  But organizations need this sense too: Banks want to give money to only the right customer, immigration officers allow only legitimate travelers into a country, and the police must arrest the criminals and not innocent passers-by.

A HISTORICAL PERSPECTIVE

In the 19th century, police tried a number of ways to identify their clients.  The best-known method was the Bertillon technique, in which an arrested person would be measured all over in great detail, so that his record would contain the lengths of his arms and legs, hands and feet, fingers and toes, as well as his height, waist, eye separation, ear shape, neck thickness and so on.  Even then, the prison uniform probably didn’t fit.  But Bertillon failed partly because of the enormous difficulty of making these highly precise measurements in the first place, and partly because the numbers were different the next time the subject was measured.  The human body is not a static lump of metal but a living, growing, changing entity.

Despite these human dynamics, one characteristic emerged that eclipsed the Bertillon dimensional analysis, and that was the fingerprint.  A fingerprint is an impression of the network of ridges on the friction surface of the skin on a finger or thumb.  If you look carefully at a fingerprint, you will see that some of the ridges suffer from interruptions in their smooth flow, i.e., either a ridge ending where the ridge stops suddenly, or a fork where it splits.  These points of interruption are called minutiae, and their layout on a plan of the ridges is extremely stable and totally characteristic of the finger.

Minutiae are so stable that a fetus in the womb has exactly the same fingerprint minutia map as he will have as a child, adult, grandparent and indeed corpse (apart from overall size, and give or take a few scars).  This stability can be described as ante-natal to post-mortem.  The uniqueness can be judged by the fact that no two fingerprints having at least eight or 10 identical points, and none different, have ever been found to come from two different fingers.  The occasional law court argument about identity via fingerprints always boils down to inaccurate testimony or problematic processing in the laboratory.

For thousands of years fingerprints have been known to be good identifiers.  We have evidence that the ancient Egyptians and the Chinese used fingerprints instead of signatures in legal documents, and pottery has been unearthed, dating back millennia, showing thumb prints that are thought to have been placed by the potter to prove the authorship of the piece.

LAW AND ORDER LYNCHPIN

Besides its stability and uniqueness, there are several other practical reasons that the fingerprint now plays such a remarkably important role in police and other law enforcement work.  First, fingerprints can be obtained from an arrested or detained person very easily, by a relatively inexperienced officer, with no risk of injury to either party, or even (using modern inkless capture) any mess.  By way of comparison, taking blood samples or shining a laser into the eye is not always as safe or straightforward.

Second, law enforcement agencies (police, border control, antiterror units, courts of law) around the world that have extensive experience with fingerprints stretching back for more than a century know how they can be used to best effect, and have access to databases of tens of millions of records.

Third, partial marks are left at crime scenes in quantities that no other biometric can rival.  A criminal never leaves a voice sample or a picture of his eye, and rarely (although it has happened) an ear print.

And fourth, the technology of automated fingerprint matching is currently very mature and well understood.  The use of fingerprints by police as a method of personal identification first occurred in Great Britain in 1901, when the Metropolitan Police set up their fingerprint department.  The New York Police followed in 1902, and the FBI in 1924.  Until the late 1970s, identification was done purely using paper.  Highly trained fingerprint examiners would look through bundles and bundles of fingerprint forms containing the finger impressions of arrested criminals until they found the one that matched the new form from a recent arrest -- or the scrappy partial latent mark obtained from the scene of a crime. It was very tedious and time-consuming work.

ADVENT OF THE AFIS

For three-quarters of a century, many attempts were made at automating fingerprint comparison, but it wasn’t until the computer became a usable tool that real progress was made.  Then it became possible to extract the minutia map and other fingerprint features automatically from an image, and to compare this map again automatically with the maps that resided in the database.  Such technology is known as an Automated Fingerprint Identification System, or AFIS.

Over the years, the question of fingerprint comparison has been addressed by some of the best experts in universities, government and industry.  Some extremely brilliant ideas have been put forward, but most have fallen by the wayside due to the normal evolutionary survival-of-the-fittest progress that guides technology.  A technique must not only provide accurate matching, but also it must be fast, robust, easy to use and simple to upgrade.  Also, if the AFIS is to be readily marketable, it can’t cost too much, and the supplier must be able to demonstrate it working on a realistically sized database.

Today there are probably only about half-dozen companies in the world that regularly build AFIS systems suitable for law enforcement and other large government and commercial interests that work with databases holding tens of millions of records.  With applications such as ID cards and passports utilizing biometrics, databases holding hundreds of millions of records will become a reality in a few short years.

Even though the use of fingerprints is more than a century old, no better method of proving personal identification has yet been devised, and fingerprinting continues to be a vital weapon in the arsenal of police forces worldwide, both as a means of maintaining accurate criminal records and detecting crime.  AFIS technology is now starting to be used not only in police, border protection and counter-terrorist applications, but also in a host of other security areas where personal identification is needed.  These areas include passports, ID cards, physical access control, time and attendance systems, and other applications.

So what does fingerprint identification offer today?  Most police forces around the world hold computer databases containing the fingerprints of recorded criminals.  A local force might have tens of thousands of records, while national forces store many millions.  For example, the FBI database contains over 40 million people, the Canadian National AFIS (RCMP- Real Time ID System) holds 4 million, and every time a new criminal is arrested, the police must determine whether that person is already on their books or is a new addition.  The AFIS must do this job in a few minutes.  Also,with international standards in place for the electronic exchange of fingerprint records, police forces and other organizations can search one another’s databases to determine, for example, if a person has been arrested in a different jurisdiction or another country.

Crime scenes reveal a slightly different picture.  As we have learned from innumerable police films and TV programs, after a crime has been committed the police technical team searches the area for any finger marks the criminal may have accidentally left behind.  These marks are often called ‘latent,’ because they can’t be seen by the eye until they are either processed using dusting powder, or worked up as part of more-complex physical and chemical processes.  Again, these partial and distorted images are compared with the fingerprints in the database to see if the perpetrator exists in the collection of criminal records.  But this kind of search is more difficult, and usually the AFIS cannot achieve a good result by itself, which requires additional help from a human fingerprint examiner who can identify fingerprint features that can be used to perform a search.

TOOL AGAINST TERROR AND FRAUD

Not just the police use fingerprint identification.  Since the Sept. 11, 2001, attacks in New York and Washington, authorities around the world have stepped up their protection against terrorists.  Visitors to the U.S. provide their fingerprints at port of entry, and these fingerprints are searched against a watchlist database that returns a ‘yes’ or ‘no’ result to an immigration official within seconds.  Other countries have introduced, or plan to introduce, similar mechanisms, including the European Union.

People-smuggling and fraudulent asylum-seeking are also growth industries.  A number of countries now regularly take the prints of all asylum applicants to check whether they have had a similar request refused in the past, or whether they might be illegal immigrants.  Again, the EU provides an international flavor by its implementation of Eurodac, a Cogent Systems AFIS that checks whether an asylum seeker has previously applied to any of the nation states in the union.  Fingerprints have also been used to establish identity for national elections.

In 2004, a voter authentication system for the government of Venezuela was provided to guarantee ‘One Voter - One Vote’ performance.  Twelve thousand authentication stations throughout the country were connected via satellite dishes at every voter center to a central AFIS to ensure the unique identity of every voter.  On the day of the election, approximately 1 million people per hour had their fingerprints captured, searched and enrolled over a period of 10 hours -- with identification results consistently returned within seconds.

Thirty years ago, when computer technology was first becoming available, an AFIS was a large, expensive, complex installation, requiring considerable expertise to run and maintain.  Even in the 1990s only large public authorities could consider such systems.  Today, what previously required a mainframe computer can be performed by a single chip, enabling AFIS identification applications on smart cards, access control devices and even handheld computers.  As fingerprint matchers and data storage units get smaller and cheaper, the deployment of AFIS units is becoming more widespread.

FUTURISTIC APPLICATIONS

Predicting the direction of technology is always a tricky job.  Speculation inevitably gets overtaken by the real world.  However, some trends appear inevitable.  One is that law enforcement and public protection will continue to loom large in our daily affairs, and that personal identification will become increasingly important.  We can envisage the time when no visitor will cross any border without being identified by a biometric device, to ensure that he is not a terrorist or an illegal immigrant.  The time is close when all police officers on the streets will carry a small fingerprint unit, maybe attached to a radio, so that a lawfully detained suspect can be instantly checked against the criminal database.

Also, many national governments are well on the way to introducing personal identity cards based on biometrics.  These will be used not just for law enforcement purposes, but to ensure that the holder is eligible to access benefits from government entitlement programs.  Biometric identification, with or without smart cards, is likely to be deployed in reducing election fraud -- as it was in Venezuela -- replacing driving licenses, ensuring that teachers or hospital staff have never been convicted of any offense that might impact their work, and so on.

Cash machines and credit card authorization are clear applications for biometrics.Imagine not having to remember a dozen PIN numbers when out shopping, but instead being required only to present your card and press a finger on the sensor in order to make a purchase or receive cash.

Fingerprint technology is also being integrated into other small consumer product such as USB memory key, PDA or mobile phones, so that it is no longer necessary to answer questions about our birth dates or mothers’s maiden names when making inquiries such as financial transactions that require positive identification.

Ming Hsieh is Chief Executive Officer of Cogent Systems Inc.  (www.cogentsystems.com).

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