Monthly Archives: April 2013

FBI Gun Collection

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Gun collection

FBI Gun Collection. Source: FBI.

 

Earlier this month, the FBI posted a story about the agency’s reference firearms collection. Started in 1933, the collection of 7,000 firearms is stored at the FBI Laboratory in Quantico, Virginia.

FBI Lab firearms examiners use the assembly of weapons to study and test firearms in support of current investigations. The library of handguns and rifles includes a database of typical marks made by the weapons, and more than 15,000 types of commercial and military ammunition. Suppressors, magazines, muzzle attachments, grenade launchers and rocket launchers also reside here.

“Oftentimes this collection is used in active cases in comparing known samples from our collection with question samples from the field,” explained FBI firearms examiner John Webb. “Often, an investigator will receive a part of a firearm or a firearm that isn’t functional. We can take that and compare it with our reference collection, determine what isn’t functioning, and repair it so we can obtain the test fires we need to conduct examinations with bullets and cartridge cases.”

 

Picturing Shoeprints

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Shoeprint

Shoeprint in blood on black nylon before enhancement (a) and after enhancement with three techniques (b, c, and d). Source: University of Abertay Dunde.

 

Last week, we saw that forensic scientists at the University of Abertay Dunde (Scotland) invented a way to recover latent fingerprints from foods. Late last year, the university’s scientists announced a new method for visualizing latent shoeprints.

Dr. Kevin Farrugia modified traditional fingerprint visualization techniques to develop the first detailed images of latent footwear marks left on fabric. Farrugia explained that a footwear mark can be created with a contaminant on the sole of the footwear and left on carpet, clothes, or a body.

“However, as the marks fade and become less visible,” Farrugia said, “the pattern on the sole of the shoe, by contrast, becomes much clearer and better defined. And it’s these prints – the ones that we can’t actually see – that are the most useful at a crime scene, especially when it isn’t possible to recover other types of evidence such as fingerprints and DNA, because they can tell you things like what size, and even what brand, of shoe the perpetrator was wearing when they committed the crime.”

These general features are class characteristics of the footwear. A print can reveal even more than this.

“[B]ecause everyone walks differently,” Farrugia explained, “the sole of their shoes will have acquired what we call random and individual characteristics that are specific to that shoe and person, which means, when the police have got a suspect, they can get their shoes, and if the shoes match, it can lead to a conviction.”

For the first time, a method can be used to produce a clear, detailed image of a latent footwear print without damaging it. Farrugia’s technique is effective with both new and old prints, and may be used to reinvestigate cold cases.

You can learn more details about this method at the Abertay University website.

 

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.