In order to help investigators find mass graves, researchers are going to create some – with pigs.
Evidence of history's great tragedies – the Holocaust, Pinochet's reign in Chile, Joseph Stalin's in the Soviet Union and genocides in Africa – often come in the form of mass graves, where hundreds (or more) of bodies are buried. Without specific evidence, these graves can take years to find, if they're found at all.
A new research project in Colombia seeks to use clues from the earth to help uncover missing "clandestine graves," whether they are from mass murders or individuals that have gone missing.
In order to test the best methods for finding a clandestine grave, Jamie Pringle of England's Keele University and his colleague, Carlos Molina, of the National University of Colombia, are setting up several "simulated graves" in Bogota, using pigs as stand-ins for human bodies. The pigs will be buried at varying depths and in different types of soil. The land will then be monitored over the course of 18 months to study how pig bodies decompose and to see whether there are any above-ground markers law enforcement can look for when searching for human grave sites.
"Pigs are very similar to humans, are of similar size, have similar organ size, body fat to tissue ratios and hair and skin types," he says.
"Conventional police intelligence, witness statements, all that stuff is good for finding mass graves," says Pringle. "But there are other things we can do to help find these isolated and mass burials."
Some of those things include different "boots on the ground" techniques – decomposing bodies give off certain types of gases, fluids and electric signatures. He says geophysicists can even use ground-penetrating radar to help find buried bodies. In some cases, the vegetation surrounding a mass grave changes as the bodies fertilize the soil.
"In some respects, mass graves are easier to find [than single clandestine graves] because there is a bigger area, there's more signatures to look for," he says. "It's not an unusual method of disposal" for mass murderers.
The longer a grave goes undiscovered, the more difficult it is to find, Pringle says. So the team is also studying graves filled with human skeletons, including some that have been burned.
"Skeletonized remains are the hardest to find," he says. "There are five well-known stages of decomposition, so if you know how long someone has been missing, you can try to collect temperature and climate information and try to look for data that corresponds to how they would have decomposed."
Pringle admits that his line of work is a bit morbid, but says that the research might one day be used to bring murderers to justice.
"It's difficult to convict a murderer without a body," Pringle says. "So that's one reason we're doing this, but it's also nice to find a body for the family, so they can have the peace of mind to know what's happened to their relatives."