Can we find hidden graves of murder victims with soil imaging? New Australian study gives it a try

Pigs at 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.

This included two single graves (a “shallow” grave of just half a metre, and a “deep” grave of almost two metres) and a mass grave with three pigs at one metre deep. We used pigs as they are a good body analogue in terms of size and mass to humans.

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

Our findings revealed that geophysical imaging of hidden graves can work, but with varying results. This depended on the size, depth and age of the burial, and the amount of rainfall before the survey.

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

A shallow single grave was the next most observable. This is also an encouraging finding because most graves of hidden victims are only around half a metre deep. For both techniques, the two-metre-deep single grave was the most difficult to image.

Although both tools could detect some graves on some occasions, neither located all of the graves during the entire length of our survey. This was likely due to a combination of factors, including the soil type at the site and unprecedented weather conditions during the research period – La Niña flooded the research site multiple times.

We did, however, confirm that pig cadaver graves are good proxies to human donor graves when investigating geophysical techniques for finding them.

To do this, we compared the ground-penetrating radar and the ERT responses of the pig burials to those of human burials (all 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 worldwide without being constrained by highly limited access to human donors.

More work needed

Similar studies have been done in the United Kingdom, the United States and South America. However, ours is the first systematic, multi-technique, geophysical survey of covert graves in an Australian environment. The only other similar Australian study was in 2004, however, it only used ground-penetrating radar and didn’t check back on the graves at multiple time points.

Our results clearly demonstrate that geophysical methods can be effective for locating unmarked graves under some circumstances, but don’t always work. To try and work out why, we will continue our research using the latest geophysical instruments and monitoring the moisture conditions inside the graves.

Ultimately, we believe using these tools can increase the chances of locating missing and murdered victims. Then, we can finally provide answers to their families and loved ones, and increase the chances of prosecuting their killers.

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 the space to conduct the research and to Soren Blau and Jon Sterenberg for allowing us to scan your graves.