Individuality of Fingerprints

In more than 100 years since fingerprint records of individuals started to be collected and compared, no two fingerprints of two different persons, including those of identical twins, have ever been found to be exactly the same. This is not only true for the ridge patterns found on the fingerprints of individuals but also of the patterns on their palms and the soles of their feet. ("The History of..." 2006) Recent studies comparing the fingerprints of cloned monkeys showed that even they have completely different fingerprints. After the introduction of AFIS (Automated Fingerprint Identification Systems), it has become possible to compare the millions of fingerprints data acquired by agencies such as the FBI and such comparisons have not found even a single case of a perfect match of two fingerprints of two different individuals; this further validates the premise about the individuality of fingerprints and gives it the status of a scientific fact.

Permanence

Permanence is one of the key features of fingerprints; it is based on the "Principle of Persistency," i.e., fingerprints are formed during early fetal life, they remain constant throughout life, and are one of the last recognizable features to disappear after death.

Ridges begin to form on the human fetus between the third and fifth months of pregnancy when the fetus is approximately 3" - 4" in length; once the pattern is formed it remains unchanged throughout a person's life. The growth of a person's fingertips along with other parts of the body containing the ridges only expands the pattern uniformly in all directions. Only deep cuts and injuries penetrating all layers of the epidermis can cause the ridge pattern to change; superficial removal of the fingerprint is not permanent as the original pattern reappears in due course.

Previous Methods of Identification

In ancient times, cruel methods such as branding and even maiming were used to mark criminals for their identification. The Romans introduced the method of tattooing their mercenary soldiers for identification purposes and in order to prevent their desertion. ("The History of..." 2006)

For a long period until the mid-nineteenth century, law enforcement officers identified criminals through their visual memories and through eyewitness accounts. Police officers were believed to possess extraordinary "camera eyes" with which they could identify previously arrested offenders by sight but the system had obvious drawbacks. With the advent of photography, the method of identification improved but it was still highly unsatisfactory since appearances of individuals can change drastically with time.

In 1870s, Alphonse Bertillon, a French law enforcement officer created anthropometry-- a system of identification based on physical measurements and record of the dimensions of certain bony parts of the body. The method, which became known as the Bertillon System, was the first scientific system police used to identify criminals but had a major flaw since appearances and sizes could always resemble and could never be absolutely permanent. (Ibid.)

How Does Fingerprinting Compare with DNA Fingerprinting?

Genetic or DNA fingerprinting, discovered in the 1980s is the latest development in forensic science which can, like conventional fingerprinting, can accurately distinguish humans from one another. This method of identification has a number of advantages over all previous methods including fingerprinting, e.g., DNA can be isolated from any part of the body, skin cells, hair, blood, blood stains or semen. Hence, even if a criminal does not leave a fingerprint behind at the scene of crime, he can be identified if his blood, hair, semen etc. is found. A dead body can also be identified from its DNA tests. Like fingerprints, DNA of no two persons can be alike except for the DNA of identical twins, which are alike. Nevertheless, fingerprinting still outperforms DNA and all other systems for identifying criminals and solves ten times more unknown suspect cases than DNA in most jurisdictions around the world. ("The History of..." 2006) This is because there is a huge database of fingerprints available with law enforcing agencies around the world, which can be cross-referenced with the fingerprints of criminals. On the other hand, DNA testing is still relatively new, requires further standardization and quality control to challenge fingerprinting universally as a forensic tool, and there are only a few reliable labs around the world that can give accurate DNA results.

The Basic Patterns & Types of Fingerprints

The patterns on the underside of our fingers and feet consist of some lines that form a continous formation, some are interrupted, others are forked, and still others make formations like...

The combination of these formations or patterns is called minutiae and provides the uniqueness of a fingerprint. In the systematic study of fingerprints, these minutiae have been divided into various basic groups. In one of the most widely used systems devised by Sir Edward Henry, the fingerprint patterns are divided into four basic groups:
Arch: a ridge that runs across the fingertip and curves up in the middle, with the tented arches giving a spiked effect.

Whorl: an oval formation which makes a spiral pattern around a central point.

Loops: These have a stronger curve than arches, and they exit and enter the print on the same side. Radial loops slant toward the thumb and ulnar loops away from the thumb.

Composites: Composites include patterns in which various combinations of the arch, loop or whorl are found in the same finger impression. (Clegg, 2004, p. 163)

When people touch a surface, these patterns on their fingertips leave a readable impression. This is because our fingers may have a visible substance such as ink, paint, or blood on them; sweat mixed with amino acids are always present in minute quantities on our fingertips and are transferred in the form of our fingerprint on the surface we touch; or pressing a finger into a moldable substance like soft wax leaves a 3-dimensional record of the fingerprint. (Ramsland, 2005)

The types of fingerprints are usually classified as:

Visible prints are the prints made in ink or blood

Latent prints are invisible, and have to made visible through certain procedures

Plastic prints are the ones left behind in moldable, soft surfaces

The most important procedure in fingerprinting technique is to make invisible prints visible because most fingerprints are invisible to the naked eye until worked on by the experts. The procedures used for 'lifting' such prints depends on the type of material on which the prints exist and it is most difficult to lift a print from irregular and absorbent surfaces. More than 40 methods of 'lifting' latent prints have been developed ranging from the basic 'powder' method to the most sophisticated by employing digital imaging, super glue and lasers. (Ibid.)

Cases of Incorrect Fingerprint Identification

Although fingerprinting for identification has long been recognized as 'infallible,' errors in fingerprint identification can and do occur. The latest such mistake was made by the FBI when it erroneously identified Brandon Mayfield, an Oregon lawyer as a participant in the March 2004 Madrid train bombings. The erroneous identification was based on the incorrect matching of one of the prints found at the scene of crime to that of Mr. Mayfield. Critics of fingerprint identification got an opportunity once again to cast doubt on the reliability of fingerprint. However, it must be remembered that the Mayfield botch-up by the FBI was more of a reflection on the misplaced over-enthusiasm of the FBI to target Muslims (Mayfield is a convert to Islam) in the wake of the 9/11 attacks rather than an inherent weakness in the reliability of fingerprint identification. (Murphy, 2004)

Other notable (and highly publicized) cases of erroneous fingerprint identification include the case of Shirley McKie, a Scottish police detective who was accused of leaving her thumb print inside a house where a woman had been murdered but was later found not guilty; and the case of Stephan Cowans who was convicted of attempted murder in 1997 while fleeing a robbery in Massacheusettes due to the evidence of a fingerprint on a glass mug; he too was later found innocent after a DNA test.

Conclusion

As we saw in this paper, the uniqueness and permanence of fingerprints have made it an indispensable identification tool that has been employed for crime fighting by the law enforcing agencies for more than 100 years. Fingerprinting is clearly superior to all the previous methods of identification including the Bertillon System that was based on physical measurements and dimensions of body parts. It even manages to hold its own against the more modern methods of identification including DNA testing and continues to be the most widely used and trusted method around the world for identifying criminals.