Science

Comparative soil analysis could drastically reduce crime search areas

Comparative soil analysis coul...
Analysis of the dirt on a suspect's car, shoes or other clothing can be used to establish where a crime took place, where a body is located, or even where a kidnapping victim is currently being held
Analysis of the dirt on a suspect's car, shoes or other clothing can be used to establish where a crime took place, where a body is located, or even where a kidnapping victim is currently being held
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A map of the sampled area, with the locations of the blind samples shown in blue
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A map of the sampled area, with the locations of the blind samples shown in blue
Analysis of the dirt on a suspect's car, shoes or other clothing can be used to establish where a crime took place, where a body is located, or even where a kidnapping victim is currently being held
2/2
Analysis of the dirt on a suspect's car, shoes or other clothing can be used to establish where a crime took place, where a body is located, or even where a kidnapping victim is currently being held

We've all seen episodes of CSI where the distinctive dirt on a suspect's shoes or car is only found in one specific location. While that scenario is a bit far-fetched, new research shows that forensic soil analysis could be used to eliminate large geographical areas from police searches.

For the study, scientists from the Geoscience Australia research group started with a 260-sq-km (100.4-sq-mi) area of north Canberra, then divided it into a grid of 1 x 1-km (0.6-mi) squares. Soil samples were taken from each square, and analyzed for distinctive characteristics such as mineral and organic matter content.

Samples from three different squares were also given to a separate group of Geoscience Australia scientists, who were only told that they came from locations somewhere in the gridded area. Utilizing techniques such as X-ray fluorescence, magnet susceptibility, Fourier transform infrared spectroscopy and mass spectroscopy, those researchers set about comparing them to the previously analyzed samples from squares at known locations.

A map of the sampled area, with the locations of the blind samples shown in blue
A map of the sampled area, with the locations of the blind samples shown in blue

Although none of the three blind samples were an exact match to just one specific grid square, it was determined that they were definitely not a match to approximately 60 percent of the squares.

"Much of forensics is about elimination, so being able to rule out 60 percent of an area is a substantial contribution toward successfully locating a sample," says the lead scientist, Dr. Patrice de Caritat. "You can reduce the time, risk and investment of the ongoing investigation. The more parameters we look at, the more accurate the system is."

The scientists are now hoping that in real-world applications, the technology could incorporate information from existing soil databases that have already been developed for fields such as mining, agriculture and urban development.

A paper on the research was recently published in the Journal of Forensic Sciences.

Source: Goldschmidt Conference via EurekAlert

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