Toronto: Canadian researchers have
developed a new technique for detecting mass graves from the
air, which they claim will help locate human remains years
after the bodies have been disposed off.
Forensic experts at McGill University in Montreal have
developed a technique, called hyperspectral imaging, which
searches for signs of chemical changes in the vegetation
growing on grave sites.
"From personal experience, I know it`s possible to miss
remains by a few centimetres, then realise it later and have
to come back," says Andre Costopoulos, a member of the team which
has used the technique for searching animal carcasses buried
at Parc Safari in Quebec.
"Even quite substantial remains within an acre can be
hard to find," Costopoulos says.
This method that analyses a range of visible and
infrared wavelengths as it scans terrain from the air could
prove useful to investigators looking for victims of war or
genocide who have been buried in mass graves, New Scientist
Cameras mounted on a light aircraft or helicopter detect
variations in the intensity of light of various wavelengths
reflected by vegetation on the ground. The precise pattern of
intensities has been found to reflect changes caused by
nutrients released into the soil as bodies decompose.
When searching for clandestine graves, investigators
traditionally look for signs of disturbance on the ground, or
dig small test trenches to identify the most likely area.
"Plants are living systems, and any changes in water
content or the soil chemistry are going to affect how they
reflect light," the team said.
The technique has great potential, says Ian Hanson, a
forensic archaeologist at the University of Bournemouth, UK,
who has investigated mass graves in Iraq and Bosnia.
"Some of these animals were buried around 20 years ago,
so you could take new imagery over areas where bodies were
buried 20, 30, 40 years ago and discover things that no one
has ever been able to find before." This could be particularly
useful in detecting older mass graves, he said.
A related method that is currently being developed by
the FBI detects living humans and recently dead bodies lying
on the ground, by recognising the chemical signature of human
skin. It could be used when trying to locate and rescue people
who are lost or missing and to track down fugitives.