Grave Hunters

McGill researchers are using remote sensing technology to unearth the secrets of war criminals.
By Peter Farbridge

McGill researchers are using remote sensing technology to unearth the secrets of war criminals.

Whether it be in Spain, Rwanda or the ex-Yugoslavia, the remains of thousands of genocide victims — men, women, children — lie in unmarked mass graves, slowly vanishing as nature reclaims the earth above them. Between the silence of the killers and vague eyewitness accounts (“You’ll find the bodies somewhere between here and the next town”), detecting these graves today is the epitome of the proverbial needle in the haystack.

But McGill researchers Margaret Kalácska (Department of Geography) and André Costopoulos (Department of Anthropology) think their research could one day coax the landscape to give up its dark past. The duo are involved in the study of remote sensing as a tool to locate hidden graves — research that could eventually put war criminals behind bars, and bring much-needed closure for grieving communities.

The core of the project is Kalácska’s five-year study of plant life anomalies on clandestine gravesites. Kalácska holds a PhD in Earth and Atmospheric Sciences. During a research position at the School of Criminology at Simon Fraser University in British Columbia, she worked with a couple of NGOs involved in missing persons and genocide investigation. “Basically, I was asked to take the tools of Earth sciences and apply them to forensic sciences,” says Kalácska from her office at Burnside Hall. “Remote sensing happened to be my specialization.”

Remote sensing works on the premise that every object emits a “signal” based on the waves of the electromagnetic (EM) spectrum it reflects back from the sun. A device called a hyper spectral sensor is able to measure that signal at very high resolutions in all EM frequencies, allowing researchers to distinguish between extremely similar objects with tremendous accuracy — it’s like being able to tell the difference between salt and sugar from across a football field using only your eyes.

Kalácska’s research compares the EM signals of plants found on gravesites with those found “off -grave.” “Their signatures have a particular shape,” explains Kalácska, clicking on the pixels of the hyper spectral cubes on her large monitor. “The plants will absorb or reflect more at different wavelengths based on the organization of their molecules and their chemical and physical properties.”

Plants that grow on human or animal graves are altered by the soil mixture below. A buried corpse will decompose when microbes in the body start to feast on the muscles and fat. As the resulting gases and liquids enter the soil, they release chemicals — toluene, nitrogen and sulfur — that are absorbed by a plant’s roots and carried up into the foliage, changing the plant’s electromagnetic fingerprint. “We can observe the wavelength regions that show us the most differences from off-grave plants and try to understand what is the biological source of these differences,” Kalácska says.

Separating the noise from the right signals is a painstaking task that involves extensive sampling of plants and soil. By comparing the samples seasonally, and in different ecological environments (she has research projects in Canada and Costa Rica), Kalácska hopes to allow archeologists to detect the presence of a mass grave in any ecosystem in the world: “If we understand the physics and have calibrated the sensors well, then we could apply the results to a much larger area.”

Nonetheless, on-site archeological confirmation will always be necessary. So when Kalácska heard about the work of André Costopoulos, she saw the makings of a perfect collaboration. The tall, eagle-eyed anthropology professor had been running a field study and public education project at Park Safari in Hemingford, Quebec, since 2007. The zoo has been interring their dead animals in a farmer’s field beside the park for three decades, and there wasn’t a good record of what was buried where. The zoologists asked Costopoulos for help in locating the remains of a seven-tone, four-metre African elephant so they could set up the skeleton in the park’s museum.

Costopoulos and Kalácska began working together, alongside soil biochemistry researcher Tim Moore, to search for the behemoth (discovering along the way a bevy of other critters, including birds, monkeys and zebras). Kalácska used an airplane equipped with hyperspectral sensors to predict where the gravesite could be; Costopoulos and his students dug to confirm her hypothesis.

“Margaret Kalácska is like a godsend for archeologists,” says Costopoulos. “The usual archeological method for finding mass graves involves making a hole in the ground every 10 metres, sometimes along hundreds of kilometres,” says Costopoulos. “Basically with one flyover, Margaret will be able to do with remote sensing what can take a team of 30 archeologists several summers to complete.”

The elephant project itself might be a bust — remote sensing confirmed a large decomposing soup that might be the animal, but the carcass is so messy that excavation is impossible — but its ramifications are far-reaching. When Frédéric Mégret learned about what was going on at Parc Safari, he immediately saw the impact on international justice. Mégret is a human rights law expert in McGill’s Faculty of Law. Thinking about the technology’s applications in criminal prosecution, he began his own research into the legal implications of Kalácska’s remote sensing images, and uncovered some surprises of his own. Fly a plane over a sovereign state to scan for mass graves, for example, and you might be in contravention of international and domestic laws. Fly a satellite over that same space, however, and you’re basically untouchable. Samuel Algozin, a student at the Faculty of Law who participated in Mégret’s research, underlined the role of remote sensing images in transitional justice as well. “This technology can serve up the ‘truth’ in ‘truth and reconciliation,’ ” he says, “helping communities who have lived conflict situations to transition to peace.”

Cauterizing historical wounds is indeed very common practice these days. Since 2002, Spain has been hunting down and exhuming the mass graves of the 114,000 men, women and children reported missing during the Spanish Civil War. Since the ethnic cleansing in Bosnia and Herzegovina in the 1990s, more than 10,000 families have submitted tracing requests to find missing relatives. And in Argentina, 25 years after the civil unrest there, Argentines are still searching for the whereabouts of 12,000 victims.

“When there’s a death but no body, it complicates the mourning process,” says Kathleen Gray, a McGill-educated counselor who specializes in traumatic loss grieving. “When people aren’t given permission to grieve, the pain can come out in destructive ways, sometimes over the long term and over generations. Seeing the deceased helps the brain to comprehend the incomprehensible.”

Given the emotional impact of the research, communities and individuals worldwide are already knocking on Kalácska’s door. One indigenous group has contacted Kalácska to enlist her help in locating the remains of ancestors buried in mass graves after a 19thcentury epidemic. Other communities are eyeing remote sensing as a way to locate pioneer gravesites.

Whatever the application, historical or criminal, one thing is for certain: Time is not a constraint in this work. “My intuition is that we’re looking at a survival period of several thousand years for these graves,” Costopoulos says. As part of his fieldwork in Northern Finland, Costopoulos has exposed the stone floors of ancient dwellings, and smelled seal oil that had been spilled there over 4,000 years ago. “If something dies and is left on the surface, it will decompose quickly. But when something gets buried underground, the evidence is going to be there for a very, very long time.”

This research is funded by the Social Sciences and Humanities Research Council of Canada, as well as the Natural Sciences and Engineering Research Council and McGill’s Faculty of Arts.