Human Error Continues to Plague Analysis of Latent Fingerprints
Sir Francis Galton, the British man of science and mathematician who introduced the first fingerprint recognition methodology in 1892, may have never imagined that, more than 100 years in the future, police investigators would utilize his watershed invention to help them – along with advanced imaging and computer analysis – apprehend suspects. Galton, who was proficient in a wide range of topics, was fascinated by the uniqueness of fingerprints, and calculated the chance of two people having the same fingerprint to be at least 1 in 64 million, based on his findings and calculations using a relatively small sample distribution. Galton analyzed the possibilities for the minutiae, that is, the simple patterns of a fingerprint’s tiny ridge lines wherever they split, end, commingle, etc. These minutiae are also called ridge characteristics, points of similarity, and now – befittingly enough – “Galton details.”
Finding, identifying, and plotting the orientation of the fingerprint minutiae enabled Galton and other early fingerprint experts to properly orient and compare two similar fingerprints to discover if they, indeed, matched. Plotting and refining the analysis of the minutiae over decades would become integral to the success of computerized automated fingerprint identification systems (AFIS) that would come forth by the late 20th century.
Technological inventions in computing have made it possible to shift fingerprint identification from its post-arrest role in the courtrooms to the police department precincts as an effective crime-solving method. Investigators today can select a suspect to pinpoint for investigation if he were fingerprinted in the course of the arrest processing or fingerprinted for certain types of security clearances for jobs, etc., known as civilian fingerprinting.
In the United States, the FBI maintains the most robust biometric database in the world with fingerprint files and criminal history files that can be accessed and searched all day, any day, by law enforcement agencies. According to the FBI, by 2010 there were records of more than 55 million subjects on file. Electronic scanning inventions have shortened the time it takes for a subject’s rolled and flat print images to be uploaded into the database, from several weeks to two hours for criminal records and 24 hours for civilian records.
Fans of TV crime series know what it means to be “in the system,” because the consequence of a match to a latent print found at a crime scene is the impending interrogation of the identified suspect. Ironically, the fascination with forensic science in books, movies, and television has produced a queer occurrence in the real-world justice system, termed by some as “the CSI effect.” Jury members who follow fictional crime-solving may attribute more credibility and trustworthiness to the professionals who appear in a real criminal trial than may be justified.
The general public watching these types of dramas may see a fingerprint image on a computer screen in a show and may think that the computer does the analysis and that the resulting ID would be all that would need to be admitted as proof. That might be feasible if suspects left full, perfect prints at the scene, because the software operates with a high stage of accuracy. The reality, however, is this: latent prints are created by oils and residues on the fingertips or contact surfaces, they may only be a partial image, and they may be of poor quality due to smudging. In fact, fingerprint identification relies on an examiner to make an eyeball comparison and confirm or dispute any preliminary match identified by the database search software.
Despite the complex engineering that has helped invent and advance biometric ID systems, fingerprint recognition has developed some blemish on its reputation. In 2004, shortly after a series of passenger train bombings in Spain, the FBI held Brandon Mayfield, a Portland, Oregon, lawyer, for two weeks after incorrect fingerprint recognition linked him to these overseas acts of terrorism. It amplified the spotlight on the factor of human fallibility in this field of forensic science. Academicians are frustrated to identify that practicing fingerprint examiners may not conduct their analyses objectively, and seem to be influenced by the context in which the prints are evaluated to a certain extent.
In one trial, the subjects had, in the past, analyzed some latent fingerprints, and were then presented with the same prints again. The second time, however, the prints were accompanied by photos of graphic violence. Surprisingly, two-thirds of the examiners drew a conclusion about the match that was different from their first findings. The researcher, a British neuroscientist named Itiel Dror, concluded that people are susceptible to cognitive and psychological impressions that clearly influenced the outcome.
Despite some evidence of human error in examining latent prints of inconsistent quality, the good news is that the automated fingerprint identification technology that uses direct scanning for security ID functions is enjoying great success. Mainstream applications of it are used to lock the contents of valuable portable consumer electronics products such as laptops and wireless phones. If these devices are ripped off, the perpetrators will not be able to access their hard drives.
The pattern-matching programs that examine the minutiae of fingertip ridges for criminal investigations have paved the way for automated biometric ID software and systems that are even more sophisticated and more capable of protecting us and our valuables, such as hand geometry, iris scanning, and facial identification.
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