A washing machine that separates important forensic evidence from soil has been developed by researchers at Michigan State University in East Lansing. They say the device could save valuable time for scene of crime investigators.

Jay Siegel, who developed the system with Alvin Smucker, says sifting soil for evidence like hairs, strands of clothing or even bomb fragments can be an arduous task.

"The old-fashioned way - rummaging through soil or vacuumed material by hand with a magnifying glass takes hours and isn't efficient," Siegel says. "You can sort for days and never see what you want."

A chance meeting between Siegel and Smucker lead to the device, known as the "Trace Evidence Concentrator", being developed. Smucker had made the device to wash delicate plant roots, but Siegel realised it could also be useful in forensics.

Bubbling over

Material sucked up by the system is dumped into a whirlpool created by jets of water. Hundreds of tiny holes in the bottom of the tank blow air bubbles up through the whirlpool to help clean the material and to float out less dense fragments.

Light material, like hairs, float to the top where they overflow into a series of filters that sift them out according to their size. Heavier material is caught in a filter at the bottom of the device.

To cut the chances of forensic evidence from one scene contaminating that from the next scene, Siegel made the insides of the device smooth and curved, so it can be cleaned easily. The device would obviously not be suitable for soluble forensic evidence like blood.

The system is currently undergoing tests and is currently on show in Washington D.C. at the Forensic Sciences and Crime Scene Technology Conference and Exposition.