Category Archives: Fingerprints

Errors in the Digital Age

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Fingerprint

 

In the digital age, fingerprints are recorded using scanners, rather than ink pads and paper. As with any new technology, the question of quality control arises. Variables ranging from a subject’s dry skin to a dirty sensor plate can produce an image that could yield an incorrect match with a fingerprint on file. The U.S. National Institute of Standards and Technology (NIST) developed a program that judges the quality of a scanned fingerprint, and indicates if a fingertip should be rescanned. NIST released the software to U.S. law enforcement agencies and biometrics researchers.

Often, films and TV shows depict a technician who declares a fingerprint match based on computer analysis. In reality, an expert makes the final decision about a match by comparing fingerprints. This eliminates computer error, but introduces human error.

The National Institute of Justice and NIST assessed the effects of human factors on forensic latent print analysis and drafted recommendations to reduce the risk of error. A copy of the 2012 report, “Latent Print Examination and Human Factors: Improving the Practice through a Systems Approach,” is available from the National Institute of Justice website. The NIJ also offers a flow chart that shows the Analysis, Comparison, Evaluation, and Verification (ACE-V) process for latent print examination used in national forensic crime labs.

Kasey Wertheim and Melissa Taylor’s article, “Human Factors in Latent-print Examination,” is another good source for information on causes for fingerprint analysis errors. The article was published in the January-February 2012 edition of Evidence Technology Magazine.

A Pioneer of Fingerprint ID

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Fingerprint card of Francesca Rojas.

Fingerprint card of Francesca Rojas, 1892. Source: National Library of Medicine.

On the evening of June 19, 1892, Francesca Rojas burst into a neighbor’s shack on the outskirts of Necochea, a small coastal village in the province of Buenos Aires. She cried that Velasquez, a laborer at a nearby ranch, had murdered her children. Velasquez had wanted to marry Rojas, but earlier in the day, she told him that she planned to marry a younger man. According to Rojas, Velasquez became furious and swore revenge.

A search of Rojas’ hut revealed the bodies of a young boy and girl with fatal head wounds. The police arrested Velasquez and questioned him. The farm hand refused to confess, even under torture. Meanwhile, rumors about Rojas began to surface. Gossipers said that a young man had told Rojas that he would marry her if she did not have the two children. Wondering if Rojas might be the murderer, the police sought help from La Plata regional headquarters.

La Plata Police Inspector Eduardo Alvarez reexamined the Rojas hut. He noticed a dark, brownish mark on the door of the children’s bedroom: the imprint of a bloodstained human thumb. Alvarez knew about the value of fingerprints. He borrowed a saw and cut a piece of the door that contained the finger mark. Alvarez returned to La Plata with the evidence and with Rojas in custody.

At the police station, he rolled Rojas’ right thumb on an ink pad, and then pressed it on a sheet of paper. Then, he called in Juan Vucetich, head of the La Plata Bureau of Identification and Statistics. Vucetich had become interested in fingerprints after reading Francis Galton’s book. He performed his own fingerprinting studies and devised a classification scheme. After Vucetich matched Rojas’ inked print with the bloody thumbprint on the door, Rojas admitted to killing her children. The case has been hailed as the earliest murder investigation solved with fingerprints.

With further research, Vucetich perfected his fingerprint identification system and published the details in his book, Dactiloscopía Comparada (1904). The Vucetich system is still used in most Spanish-speaking countries.

Introduction to Fingerprints

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Image from Henry's book

Image of a whorl pattern that appears in Henry’s book. (Source: National Library of Medicine).

One of the oldest types of evidence used in criminal investigations is the fingerprint. During the 1870s, Henry Faulds, a Scottish doctor working in a Tokyo hospital, studied fingerprints as identifying marks. After he applied his research in a criminal case, Faulds offered to fund a fingerprint bureau at Scotland Yard. But police officials were not interested.

Faulds published his observations about fingerprints in 1880. The report came to the attention of Francis Galton, a nephew of Charles Darwin. Galton investigated fingerprints and concluded that fingerprints remain the same during an individual’s lifetime, and that no two fingerprints are identical. He suggested a system of fingerprint identification in his book, Finger Prints (1892).

Eight years later, Edward R. Henry, Commissioner of the Metropolitan Police, published his book, The Classification and Use of Finger Prints, which also proposed a method of fingerprint classification. New Scotland Yard launched a three-person Fingerprint Branch in July 1901. The department used the Henry system of classification, which has become the core of fingerprint systems in most English-speaking countries.

Prepared by the International Association for Identification, The Fingerprint Sourcebook (2011) is an excellent resource for many aspects of fingerprint identification practice. The National Institute of Justice offers a free copy of the book on its website.