The same LIDAR technology that lets driverless cars “see” their surroundings can be used to spot changes in a landscape indicative of grave sites
13 August, 2018
When the war in Bosnia ended, more than 20 years ago, some 100,000 people were dead. Of the casualties, more than 30,000 bodies were reported missing, most buried in unmarked graves. Today, some 6,500 are still unaccounted for.
A decade after the war, forensic anthropologist Amy Mundorff was visiting a friend in Bosnia working to find some of these graves. The team was relying mostly on witness testimony, using backhoes to dig up the ground where locals remembered seeing burials. But at the end of the day, they left empty-handed.
“There was nothing there,” Mundorff says.
Memories are fallible. Ground shifts. Landmarks come and go.
There had to be a better way, Mundorff thought.
Now a professor at the University of Tennessee, Mundorff began to explore a technology best known to most of us for enabling driverless cars to “see” their surroundings: LIDAR. The light detection and ranging technology involves shooting pulses of infrared light and measuring the time it takes for them to bounce back. The technology is used in a number of fields in addition to driverless cars, including map-making and archaeology, where it allows scientists to spot ruins through thick forest canopy.
For her research, Mundorff turned to one of her university’s most unique facilities: the Forensic Anthropology Center, sometimes known as the “Body Farm.” Here, on a 2.5-acre wooded plot of land, forensic scientists study the decomposition of human bodies buried in shallow graves, locked in car trunks and pinned underwater, among other staged scenarios. One of just a handful of such facilities in the country, it’s been helping forward forensic science and crime scene investigation since it opened in 1981. All the bodies are donated—more than 100 people donate their bodies to the center every year.
“We appreciate the people who donate their remains,” Mundorff says. “It’s important to recognize them because without them we couldn’t do this type of research.”
Mundorff and her colleagues distributed 10 donated bodies in three graves: a single grave, a three-person grave and a six-person grave. A fourth, body-less, grave served as a control. The team then flew LIDAR-equipped helicopters over the facility four times over a period of nearly two years. They found the LIDAR was able to detect changes in the ground where the graves were located, even at the end of the study when the ground was more settled and the graves covered in vegetation.
The key to the research was watching for changes in the ground over time. This requires having a previous map of the landscape, though as most parts of America have been fairly well-mapped this isn’t much of a problem domestically, Mundorff says.
If there’s a grave in the ground, you’ll initially see an elevation increase, where the soil is less compact and the mass of the body is present, she explains. Then, as the soil settles, they’ll be a drop in soil elevation. Then, depending on the environment and how deeply the bodies are buried, there will often be a secondary drop in elevation as the body decomposes and the dirt falls in to the skeleton.
Mundorff hopes the LIDAR technique can eventually help deal with some of the shortcomings of current grave-finding methods. There are two different basic types of grave-finding, she explains: destructive and non-destructive. Digging up the dirt with backhoes is a destructive technique.
“It can be helpful, but it can also destroy evidence,” Mundorff says. “And unless you have really excellent witness testimony or other types of evidence as to where [the graves are], it’s just a lot of time and money and effort.”
Cadaver dogs are rarely successful unless the grave is fresh and shallow.
“If it’s buried deep, if it’s old and decomposed, there’s no scent for them to pick up,” she says.
Aerial surveys—flying over the land taking pictures—is non-destructive, and extremely useful for recent graves, Mundorff says, as it can detect the “scars” when the ground has been disturbed. But once the dirt is overgrown with vegetation it becomes much less useful.
Mundorff sees the LIDAR tests as a proof of concept, and hopes to secure more funding to study the issue further. In particular, she wants to research how well the LIDAR can penetrate different types of forest canopy at different times of year.
“I am glad that someone is doing research in this area, as looking for a surface depression is a sound way to search for potential clandestine graves, and they were able to quantify the formation of depressions over a decomposing body over time,” says James Pokines, the forensic anthropologist for the state of Massachusetts, who teaches forensic anthropology at the Boston University School of Medicine.
Pokines cautions that “boots on the ground” will still be needed to investigate any depressions located by the LIDAR system, but that having the search area narrowed down could be very helpful.
If successful, the technology could one day be used in places like Bosnia—or Lebanon, or Mexico, or Rwanda—anywhere people have gone missing in wars, conflicts or genocides. It could also be used by local law enforcement agents looking for murder victims; the LIDAR could potentially be mounted to drones, making it cheaper and more accessible.
“Myself, I’d like to see it used more internationally, in humanitarian and human rights investigations,” Mundorff says. “Because when you can’t find the bodies and the evidence, it leads to impunity.”