Fingerprints

  A fingerprint in its narrow sense is an impression left by the friction ridges of a human finger. The recovery of fingerprints from a crime scene is an important method of forensic science. Fingerprints are easily deposited on suitable surfaces (such as glass or metal or polished stone) by the natural secretions of sweat from the eccrine glands that are present in epidermal ridges and  also  afford an infallible means of personal identification because the ridge arrangement on every finger of every human being is unique and does not alter with growth or age. Fingerprinting is one form of biometrics, a science which uses people’s physical or biological characteristics to identify them. This enables them to be used as evidence in a crime.
Fingerprints serve to reveal an individual’s true identity despite personal denial, assumed names, or changes in personal appearance resulting from age, disease, plastic surgery, or accident. The practice of utilizing fingerprints as a means of identification, referred to as dactyloscopy, is an indispensable aid to modern law enforcement. Injuries such as superficial burns, abrasions, or cuts do not affect the ridge structure or alter the dermal papillae, and the original pattern is duplicated in any new skin that grows.
They are also unique and never change, even as you get older unless the deep or ‘basal’ layer is destroyed or intentionally changed by plastic surgery. In other words, no two people have the same fingerprints, not even identical twins. There are three main fingerprint patterns – these are called arches, loops and whorls. It is the shape, size, number and arrangement of minor details in these patterns which makes each one unique.

The beginning 
The interest in modern fingerprint identification dates from 1880 when the British scientific journal Nature published letters by the Englishmen Henry Faulds and William James Herschel describing the uniqueness and permanence of fingerprints. Back in 1892 Francis Galton, who suggested the first elementary system for classifying fingerprints based on grouping the patterns into arches, loops, and whorls. Galton’s system served as the basis for the fingerprint classification systems developed by Sir Edward R. Henry, who later became chief commissioner of the London metropolitan police, and by Juan Vucetich of Argentina. The Galton-Henry system of fingerprint classification, published in June 1900, was officially introduced at Scotland Yard in 1901 and quickly became the basis for its criminal-identification records. Juan Vucetich, an employee of the police of the province of Buenos Aires in 1888, devised an original system of fingerprint classification published in book form under the title Dactiloscopía comparada (1904; “Comparative Fingerprinting”).

Identification
When a fingerprint is found at a crime scene, this is known as a ‘finger mark’ or ‘latent print’. By cross-checking these against other prints in police databases, these prints have the potential to link a series of crimes together or to place a suspect at the scene of a crime. Fingerprints can be taken either with an electronic scanning device or manually using ink and paper. A scanner is then used to save the data electronically in the appropriate format. While most national police have their own country database of fingerprints, INTERPOL has an international fingerprint database which we call the automatic fingerprint identification system (AFIS). Through the AFIS gateway, users receive the results of their checks very quickly. And it is used for:
-individuals who are unknown in the database, this takes only a few minutes (automatic search)­
– individuals known in the database, this takes about an hour (semi-automatic search)­
– unidentified latent prints from a crime scene, this takes about an hour (manual process)
The automated process means the database can make more than 1,000 comparisons per day. The system is also capable of searching and filing palm prints.

 

But…

In a recent report, the American Association for the Advancement of Science has questioned the scientific validity of fingerprint analysis. Although fingerprinting is an essential tool for investigating crime, it’s not infallible. We need to minimise the inappropriate application of the “science” of fingerprinting and reduce repeats of miscarriages of justice linked to fingerprint analysis that have already occurred. For instance, most notoriously, Brandon Mayfield, an American lawyer, was wrongly linked by four fingerprint experts to the 2004 Madrid train bombing. He was arrested and detained for two weeks before investigators realised that an Algerian man, Ouhnane Daoud, was the real source of the print. One of the main reasons for these high error rates is that fingerprint analysis involves human judgement, and relies on a methodology (known as “ACE-V”) that is not sufficient to ensure the accuracy and reliability of an examiner’s conclusions. This means there is no guarantee that two different examiners who follow its steps will reach the same result since the National Research Council report was released, scientists have worked hard to prove that fingerprint examination is scientific.

Research has now convincingly established that the ridge patterns on fingers vary greatly among individuals and that there is little variation in a person’s fingerprints over time. This provides a scientific basis for using fingerprints to distinguish individuals, even identical twins. But there is still no scientific basis for concluding that a print must have been left by a specific person, or even for estimating the number of people who might be the source of a print. Because fingerprint analysis depends heavily on human judgement, an examiner’s conclusions may be improperly influenced by non-scientific factors, such as irrelevant contextual information. This phenomenon, which is known as “cognitive bias”, has been demonstrated in various studies.

While these reports and studies indicate a need for caution when relying on fingerprint examinations, they do not mean that police should stop using fingerprints. Fingerprinting is an essential tool for investigating crime and should continue to be used for this purpose. But steps need to be taken to limit the likelihood of future miscarriages of justice.