A Low Cost Approach to Disturbed Soil Detection Using Low Altitude Digital Imagery from an Unmanned Aerial Vehicle

Ground penetrating radar and electrical resistivity tomography surveys with a subsequent intrusive investigation in search for the missing Beaumont children in Adelaide, South Australia

Jane, Arnna, and Grant Beaumont went missing from Glenelg Beach in Adelaide, South Australia on 26 January (Australia Day) 1966. Despite multiple land and sea searches over nearly 60 years, the children have not been found. New credible eyewitness testimony led to a site of interest at the now disused New Castalloy factory in North Plympton, Adelaide. This site has a complex stratigraphy of anthropogenic fill, which made ground penetrating radar (GPR) investigations unpromising. Electrical resistivity tomography (ERT), while not commonly used in a forensic capacity, provided an alternative approach that allowed suitable depth penetration to resolve a feature of interest, which was subsequently excavated by the South Australia Police. This feature did contain organic, and animal remains but, sadly, not the grave of Jane, Arnna, and Grant Beaumont. However, this investigation highlights the potential to use ERT in a forensic capacity, as well as the limitations of using geophysical techniques for covert burial detection.

The suitability of using domestic pigs (Sus spp.) as human proxies in the geophysical detection of clandestine graves

Research in many forensic science fields commonly uses domestic pigs (Sus spp.) as proxies for human remains, due to their physiological and anatomical similarities, as well as being more readily available. Unfortunately, previous research, especially that which compares the decompositional process, has shown that pigs are not appropriate proxies for humans. To date, there has not been any published research that specifically addresses whether domestic pigs are adequate human proxies for the geophysical detection of clandestine graves. As such, the aim of this paper was to compare the geophysical responses of pig cadavers and human donor graves, in order to determine if pigs can indeed be used as adequate human proxies. To accomplish this, ground penetrating radar (GPR) and electrical resistivity tomography (ERT) responses on single and multiple pig cadaver graves were compared to single and multiple human donor graves, all of which are in known locations within the same geological environment. The results showed that under field conditions, both GPR and ERT were successful at observing human and pig burials, with no obvious differences between the detected geophysical responses. The results also showed that there were no differences in the geophysical responses of those who were clothed and unclothed. The similarity of the responses may reflect that the geophysical techniques can detect graves despite what their contents are. The study implications suggest that experimental studies in other soil and climate conditions can be easily replicated, benefiting law enforcement with missing persons cases.

Drone aerial imagery for the simulation of a neonate burial based on the geoforensic search strategy (GSS)

A woman reporting the homicide and burial of an infant in 2004 prompted the creation of an experimental simulated neonate grave shortly before the real search commenced. The real case, documented here, did not use aerial imagery, but used ground-penetrating radar (calibrated to the test site described here) to identify two locations that were probed for gas release and the deployment of victim recovery dogs. We suggest technological advances in remotely sensed aerial imagery that have developed since 2004 will demonstrate their use in focusing such searches by informing a Geoforensic Search Strategy (GSS) and suggesting locations accessible by a perpetrator to identify a burial location using the still-existent analogue site. To test this, in the spring of 2020 a DJI Mavic Pro drone was flown over the control site containing the simulated 2004 burial. Aerial image processing included the creation of orthomosaics, Normalised Difference Vegetation Index (NDVI), Visual Atmospheric Resistance Index (VARI), and photogrammetry. Conventional ground-based geophysical surveys using ground-penetrating radar, guided by this new type of information integrated into the GSS, confirmed that anomalies seen in drone data were the 16-year-old burial. We test this strategy using both the original simulated burial in Northern Ireland and further evaluate it in two recent simulated graves in the United States in more complex scenarios, but with successful results.