Can Hidden Graves of Murder Victims Be Found Using Soil Imaging? New Australian Study Attempts to Do Just That

To avoid being caught, murderers often attempt to conceal the bodies using various methods: shallow or deep burial, immersion in water, encasing in concrete, or disposing of the remains in trash cans or suitcases.

The search for the body is a key part of any murder investigation, as it helps identify, prosecute and charge the killer. Unfortunately, the task can be extremely difficult.

To solve the problem of locating hidden graves, we tested two innovative underground search techniques: ground-penetrating radar and electrical resistivity tomography, or ERT. Our results are now published in the journal Remote Sensing.

Borrowing tools from geology

The tools we used are known as geophysical methods because they measure the physical properties of materials present in the ground below the surface.

Using geophysical techniques to peer into the Earth’s surface is not new: engineers, geologists, and archaeologists have been using the tools we’ve been testing for decades.

But geophysical techniques are not generally used for forensic investigations because directly Finding a body with these methods is very difficult.

However, both tools we tested can help locate a grave. indirectly – by looking at differences between the disturbed soil of the grave and the undisturbed soil around it. When the techniques detect disturbed soil and/or the presence of bodily fluids, the resulting data presents itself as an anomaly – something different from the surrounding areas.

To determine if the identified anomaly is a grave, researchers can then consider the size, shape, and depth of the anomaly to ensure it is consistent with a human body.

The pigs of the “body farm”

At the Australian Facility for Taphonomic Experimental Research (AFTER), Australia’s only “body farm” – a facility that uses donated bodies for forensic research – we buried five pigs in various configurations to mimic clandestine graves.

These were two individual graves (a “shallow” grave of just half a meter and a “deep” grave of almost two meters) and a mass grave with three pigs at a depth of one meter. We used pigs because they are a good body analogue in terms of size and mass to humans.

We inspected the graves with ground-penetrating radar and ERT before and just after burial, and then one, eight, 14 and 20 months later.

Our results revealed that geophysical imaging of hidden graves can work, but with variable results. This depends on the size, depth and age of the burial, as well as the amount of precipitation prior to the study.

The pit containing the three pig corpses was the easiest to observe due to its larger size and volume. This indicates that geophysical techniques can be particularly useful in humanitarian investigations that involve searching for mass graves.

The second most easily observed grave is a simple, shallow grave. This is also an encouraging discovery because most hidden victim graves are only half a meter deep. For both techniques, the two-meter-deep simple grave was the most difficult to photograph.

Although both tools were able to detect some graves on some occasions, neither managed to locate all graves over the entire duration of our study. This was likely due to a combination of factors, including the soil type of the site and unprecedented weather conditions during the research period (La Niña flooded the research site on several occasions).

However, we have confirmed that pig carcass graves are good substitutes for human donor graves when investigating geophysical techniques to find them.

To do this, we compared the GPR and ERT responses from pig burials to those from human burials (both part of existing research projects at AFTER). We found no obvious differences between the two.

This is a very important result because it means we can further test these tools in Australia and around the world without being limited by very limited access to human donors.

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Read more: Secrets wrapped in cloth: How our study of 100 rotting pig bodies will help solve crimes

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There is still work to be done

Similar studies have been conducted in the UK, USA and South America. However, our study is the first systematic, multi-technique geophysical study of hidden graves in an Australian environment. The only other similar Australian study was conducted in 2004, but it used only ground penetrating radar and did not repeatedly check the graves.

Our results clearly demonstrate that geophysical methods can be effective in locating unmarked graves in some circumstances, but do not always work. To try to understand why, we will continue our research using the latest geophysical instruments and monitoring moisture conditions inside the graves.

Ultimately, we believe that using these tools can increase the chances of finding missing or murdered victims. We can then finally provide answers to their families and loved ones, and increase the chances of prosecuting their killers.

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The team would like to thank Justin Ellis, Gabriel C Rau, Dilan Seckiner, and Isabella Crebert for their contributions to this research. Additionally, we would like to thank AFTER for providing space to conduct the research and Soren Blau and Jon Sterenberg for allowing us to scan your graves.