Tag Archives: fingerprints

Exposing Fingerprints

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Fingerprint

 

During July, the University of Leicester Press Office posted a report about a new technique for visualizing latent fingerprints from crime scenes. Visualizing usable latent fingerprints poses a challenge; about 10% of crime scene fingerprints have sufficient quality to be used as evidence during a trial.

The new technique exposes fingerprints by using the electrically insulating properties of a fingerprint’s sweat and oil deposits. The chemicals in a fingerprint block an electric current used to deposit a colored, electro-active film. The deposited film collects on the surface between fingerprint deposits to create a negative image of the fingerprint. The technique is very sensitive and can be used in combination with traditional visualization techniques, such as fingerprinting powders.

“By using the insulating properties of the fingerprints to define their unique patterns and improving the visual resolution through these color-controllable films,” said team leader Professor Robert Hillman in a press release, “we can dramatically improve the accuracy of crime scene fingerprint forensics. From the images we have produced so far, we are achieving identification with high confidence using commonly accepted standards.”

 

Snacking with Conviction

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Food behind bars

 

When criminals snack at a crime scene, they leave evidence behind. A bitemark in half-eaten food is one type of evidence. Peckish criminals also leave DNA and fingerprints.

Last week, Ryan Pfeil of the Medford Mail Tribune (Oregon) reported that burglary is a thirsty business. Burglars broke into a house through a garage and stole a flat-screen television, jewelry, and other valuable items. The burglars also took a container of orange juice from the refrigerator, drank from it, and left the container in the garage on their way out. Investigators sent the container to the Oregon State Crime Lab for tests.

Lab techs found DNA and fingerprints on the carton. They also found a match between one DNA sample and a DNA profile in the FBI database. The DNA match led investigators to a 33-year-old man who faces charges of first-degree theft, aggravated theft and burglary.

Around the same time, forensic scientists at the University of Abertay Dunde (Scotland) announced that they recovered latent fingerprints from foods.

“Although there are proven techniques to recover fingerprints from many different surfaces these days, there are some surfaces that remain elusive, such as feathers, human skin, and animal skin,” former crime scene examiner Dennis Gentles explained. “Foods such as fruits and vegetables used to be in that category, because their surfaces vary so much – not just in their color and texture, but in their porosity as well. These factors made recovering fingerprints problematic because some techniques, for example, work on porous surfaces while others only work on non-porous surfaces.”

University scientists overcame the problem by modifying a technique designed to recover fingerprints from the sticky side of adhesive tape. You can learn more about this breakthrough at the Abertay University website.

 

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.