In an early blog post, Alice mentioned that ground penetrating radar (GPR) was used to locate an “anomaly” at a site where a tip suggested the children were buried. Some latched on to this which is common behaviour in missing children cases.
I am going to approach this discussion in a somewhat chronological manner. That is, despite knowing the outcome of the excavation of the anomaly, I am going to first review how GPR works and what it can and cannot do. Then I will discuss the findings with regards to the excavation.
As a scientist with a background in forensic investigation, one of the first rules is to keep an open mind and not to assume something until you have firm evidence. When it comes to technology such as GPR anomalies are just that: something that differs from the surrounding ground profile for some reason. Reading the output of GPR for a relative novice is something akin to that scene in one of the Harry Potter films where the trio of main characters are learning to read tea leaves. You have to check assumptions at the door to avoid an expectation- say…. locating the graves in the most famous missing children case in Australian history- leading to an illusory correlation. You think the Beaumont children are buried at a given location and you find an odd reading on the GPR at that spot. The scientifically and forensically sound approach is to flag the spot and excavate before assuming anything about what is down there.
The reason for this is that the images produced by a GPR unit are NOT like looking at a side scan sonar image or CT scan producing a three-dimensional rendering of the target. You are getting a two-dimensional depiction of how readily a given set of soil layers allow microwave electromagnetic radiation to pass through or the degree to which they are reflected, refracted or scattered back to the unit.
This is not the Jurassic Park technology (which, by the way, does not exist to my knowledge) that allowed the characters to image a Velociraptor skeleton with amazing clarity; first, that used sound waves and second, GPR doesn’t work like that. A lot of people think of that scene when you mention the use of this technology.
A good example is the following image of a historic cemetery. The arrows indicate potential grave sites. Key word, even in a known cemetery: potential. There are many things that can change the soil profile on GPR. Differences in water content, soil makeup (sand vs rock vs clay), electrical conductivity and disruption of the normally orderly layering by human intervention (i.e. digging or compacting the soil), animal intervention (burrowing) or geological processes all can alter the returns one can achieve.
If you have a soil profile that is heavily composed of rock or very fine sediments (clay or silt), you are probably going to have a problem with getting good quality images although for different reasons. Very fine sediment tends to attenuate the signal very rapidly. That is to say that the signal simply does not penetrate very far or provide good resolution. Rocky or uneven soil mixes will scatter the signals and make interpretation more difficult or at times impossible.
I will point out that you CAN get three-dimensional images if you have the technology and the time. I have never seen “real time” three-dimensional GPR in the field most likely because of cost. The alternative procedure can be time-consuming because it amounts to “stitching together” the individual readings to create the image. Even “basic” GPR costs enough that only very large organisations have their own with most teams (forensic or archaeological) hiring a contractor who specialises in the technology. Even if you have a three-dimensional rendering, the likelihood of having sufficient resolution to detect fifty year old juvenile skeletal remains is vanishingly small.
Without getting into anything too graphic, I should point out that at this point it is unlikely that a search and excavation – no matter how thorough – is likely to turn up what most people imagine when you say “skeletal remains”. Ground water, the pH level of the soil, bacteria, fungi, the simple weight of the overlying soil all have had a very long time to alter the condition of the remains. It is hard enough on the comparatively denser and more robust remains of an adult let alone juvenile skeletal elements.
At a site like a factory, anomalies are going to be quite common as you have a site that may have been extensively altered for mundane reasons such as construction, improving water drainage or disposal of waste products, construction debris, etc. Without seeing the images, I cannot even begin to- in good faith at least- say anything about the probability of the anomaly being a burial site let along THE burial site. Even if I were granted access, I am not inclined to dig my heels in and state that it is a grave. The only way to determine what is down there with certainty is to dig.
That is why a forensic team excavated the site of the anomaly. The find turned up only animal bones which has confused some as to why there would be animal bones at a site where someone reported the burial of three children. The first answer is pretty simple: if you look over any area suitable for disposing of human remains, you are likely to find some form of animal bone. Now whether this was the intentional burial of a pet or some form of wildlife, I am not sure. All the reports I have seen have simply stated “animal bones”. If this was not an intentional burial, there are several burrowing animals in Australia and a collapsed den could conceivably produce a GPR signature similar to that of a grave.
On a related note, I feel professionally obliged to point out that the children may not have been buried at all- or were buried very shallowly – and the remains may have been encountered at some point without being recognised as human. The skeleton of a child especially when incomplete and fragmented or weathered would be hard for most people to look at and go “That’s human”. Even elements that people would think of as obviously human are not so clear-cut when dealing with young children. The teeth are about the only thing I would wager anything on a random person on the street being able to pin down as human if provided with an assortment of broken and eroded elements. This sort of thing is why one author estimated that 20% or more of the specimens presented to a forensic anthropologist turn out to not be human.
A skull of a very young child is only partially fused together from an assortment of components and it often comes apart or fragments. Pieces of some elements of a rabbit’s skeleton have been mistaken by inexperienced responders for the bones of an infant at the scene of a fire. The reverse could also happen and an average person randomly encountering a bone or bones when not actively looking for human remains is going to logically assume it is from an animal versus a child. The Beaumont children may have been “found” decades ago without anyone taking serious note of it. It is a gut wrenching thought to be sure but it should not be taken in any way as a suggestion to give up further searches. Nor is this a condemnation of anyone who might have been in a position to overlook the remains. We still owe it to the children and to their families to keep looking so long as there are leads or clues to pursue.
At this point in the case and given what I just said, I am reminded of the motto of the fictitious Bureau for Paranormal Research and Defense of the Hellboy comics series: In absentia lucis, tenabrae vincunt. In the absence of light, darkness prevails. The darkness here is more than just the abduction and murder of these three innocents. It is more than the grief and emotional vacuity left in the lives of the Beaumonts by the children’s loss.
Darkness here can be as ethereal, nebulous and intangible as the duty a society owes to its members to do everything possible to assure that we do not leave the fallen unaccounted for. It is a sentiment normally expressed towards those missing in service to their country in wartime. It applies just as well to the victims of the inhumanity that stalks the periphery of our daily existence. We are not obligated to complete the task set before us but neither are we free to abstain from it be that work the frustratingly mundane or the heartbreakingly macabre.
My hat is off to the police, my colleagues in Australia, the volunteers and everyone else who have not let this case simply become a footnote. So we are left in the same place we began: no ready answers to a frustrating case. I hope you find yourself better versed on what ground penetrating radar can and cannot do in the real world and the possibilities of finding answers to the mystery.
Steve is the executive director of Kolibri Forensics, a nonprofit startup providing forensic search and recovery services and conducting research into various aspects of forensic science. His background includes being a former deputy coroner and serving on two disaster victim identification teams at the state and international level. He has several publications to his credit and has been an educational speaker at forensics, medical and emergency services conferences in the United States, Canada and Europe. He is currently in the process of applying for his Royal Anthropological Institute certification at the Forensic Anthropologist III level. He will be starting his master’s degree in forensic anthropology later this year.