Drone-based timelapse documentation of forensic burials: A pilot study

Forensic burials are used by perpetrators to dispose of evidence, including victims of homicide, as well as drugs, weapons, and other relevant evidence. There are many search techniques available that can increase the chances of locating these forensic burials, each with their own set of indicators that allow the grave to be identified. It is important as an investigator to understand not only the search technique being used, but what makes the grave detectable using that technique, depending on the time since burial and the contents of the grave. The aim of this pilot project was to aerially document the timelapse visible grave-related surface changes of three simulated forensic burials - full-sized pig cadaver (to mimic human remains), plastic cast teaching skeleton (to mimic other kinds of evidence), empty grave (to act as a control). The methods include systematically surveying the graves over a one-year period using a DJI Mini Pro 4, including uncrewed aerial vehicle (UAV)-photography, used to document the grave surface changes, and UAV-photogrammetry, used to quantify the subtle and localised grave elevation changes. The results showed that the lack of plant life over the grave areas and the backfill halo were the most helpful grave surface changes, however, they ceased being identifiable on days 328 and 93 post burial, respectively. While vegetation regrowth occurred at a similar rate across the different burial types (day 328 for the cadaver grave and 366 for empty and non-cadaver graves), the only burial to demonstrate an elevation change was the cadaver grave which mounded at first, reaching its peak on day 8 and slowly and continually depressing until it was flattened on day 233. The study implications include demonstrating cost-effective UAV drone-based grave documentation, providing specific intelligence on useful grave indicators for forensic burial searches.