Geophysical Monitoring of Simulated Clandestine Graves Using Electrical and Ground‐Penetrating Radar Methods: 0–3 Years After Burial*,†

Abstract: This study provides forensic search teams with systematic geophysical monitoring data over simulated clandestine graves for comparison to active cases. Simulated “wrapped” and “naked” burials were created. Multigeophysical surveys were collected over a 3‐year monitoring period. Bulk ground resistivity, electrical resistivity imaging, multifrequency ground‐penetrating radar (GPR), and grave and background “soil‐water” conductivity data were collected. Resistivity surveys revealed the naked burial had consistently low‐resistivity anomalies, whereas the wrapped burial had small, varying high‐resistivity anomalies. GPR 110‐ to 900‐MHz frequency surveys showed the wrapped burial could be detected throughout, with the “naked” burial mostly resolved. Two hundred and twenty‐five megahertz frequency GPR data were optimal. “Soil‐water” analyses showed rapidly increasing (year 1), slowly increasing (year 2), and decreasing (year 3) conductivity values. Results suggest resistivity and GPR surveys should be collected if target “wrapping” is unknown, with winter to spring surveys optimal. Resistivity surveys should be collected in clay‐rich soils.     

Controlled GPR grave research: comparison of reflection profiles between 500 and 250 MHz antennae

Since ground-penetrating radar (GPR) has become a popular search option for clandestine graves, controlled research is essential to determine the numerous variables that affect grave detection. The purpose of this study was to compare GPR reflection profiles of a controlled grave containing a large pig carcass and a blank control grave at 6 months interment in a Spodosol, which is a common soil type in Florida. Data collection was performed in perpendicular orientations over the graves using both 500 and 250 MHz antennae. Since reflection profiles are used to make initial in-field assessments during a forensic search, it is important for controlled research to evaluate this imagery option. Overall, it was possible to detect the grave containing a pig carcass at 6 months interment that was buried in a Spodosol using both the 500 and the 250 MHz antennae. While the 500 MHz antenna provided more detail within the grave containing a pig carcass, including detecting a soil disturbance and the pig carcass, the 250 MHz antenna also provided excellent imagery. Either antenna would provide optimal results for the type of soil that was sampled. Furthermore, it may be possible to locate actual forensic graves in this soil type when no response from the body is noted, as there may be a discernable response from the disturbed soil within the grave shaft and a noticeable disruption of the spodic horizon. Finally, survey orientation may also affect detection. Since data collection performed in two perpendicular directions detected the pig carcass and the grave floor of the control grave, data collection for an actual search involving a body interred for a long postmortem interval should be performed in both directions when time permits.     

Long‐term Geophysical Monitoring of Simulated Clandestine Graves using Electrical and Ground Penetrating Radar Methods: 4–6 Years After Burial

This ongoing monitoring study provides forensic search teams with systematic geophysical data over simulated clandestine graves for comparison to active cases. Simulated “wrapped,” “naked,” and “control” burials were created. Multiple geophysical surveys were collected over 6 years, here showing data from 4 to 6 years after burial. Electrical resistivity (twin electrode and ERI), multifrequency GPR, grave and background soil water were collected. Resistivity surveys revealed that the naked burial had low‐resistivity anomalies up to year four but then difficult to image, whereas the wrapped burial had consistent large high‐resistivity anomalies. GPR 110‐ to 900‐MHz frequency surveys showed that the wrapped burial could be detected throughout, but the naked burial was either not detectable or poorly resolved. 225‐MHz frequency GPR data were optimal. Soil water analyses showed decreasing (years 4 to 5) to background (year 6) conductivity values. Results suggest both resistivity and GPR surveying if burial style unknown, with winter to spring surveys optimal and increasingly important as time increases.     

Establishing forensic search methodologies and geophysical surveying for the detection of clandestine graves in coastal beach environments

A 2010 UK police search for a clandestine burial highlighted the need for more information and quantitative data to aid coastal beach searches. This study aimed to address this by establishing relevant forensic search methodologies to aid the search for clandestine coastal burial sites, using the North West English coastline as a search area. A set of parameters were established, including criteria such as tidal range, proximity to vehicular access points and distance from inhabited areas, which may inform forensic searches by prioritising likely locations of clandestine burials. Three prioritised coastal locations were subsequently identified: (1) coastal dunes at Formby, (2) coastal dunes and (3) beach foreshore at Southport, all sites part of the Liverpool City Region in the United Kingdom. At all locations, simulated clandestine graves were hand-dug by spades into which a naked adult-sized, metal-jointed fiberglass mannequin was buried at 0.5 m below ground level. Trial geophysical surveys were then undertaken with the aim of identifying the optimal geophysical instrumentation and technique to deploy in such environments. GPR data showed 450 MHz frequency antennae to be optimal, with significantly poor data obtained from the foreshore area due to saline seawater. Electrical resistivity and magnetic susceptibility surveys were successful in coastal environments in target detection (albeit not in non-vegetated sand dunes), with resistivity fixed-offset configurations deemed optimal. The latter survey successes may be due to the recent disturbed 'grave' rather than the target, which itself is of interest in terms of identifying the most recent clandestine burials.     

Time-lapse geophysical investigations over a simulated urban clandestine grave

A simulated clandestine shallow grave was created within a heterogeneous, made-ground, urban environment where a clothed, plastic resin, human skeleton, animal products, and physiological saline were placed in anatomically correct positions and re-covered to ground level. A series of repeat (time-lapse), near-surface geophysical surveys were undertaken: (1) prior to burial (to act as control), (2) 1 month, and (3) 3 months post-burial. A range of different geophysical techniques was employed including: bulk ground resistivity and conductivity, fluxgate gradiometry and high-frequency ground penetrating radar (GPR), soil magnetic susceptibility, electrical resistivity tomography (ERT), and self potential (SP). Bulk ground resistivity and SP proved optimal for initial grave location whilst ERT profiles and GPR horizontal "time-slices" showed the best spatial resolutions. Research suggests that in complex urban made-ground environments, initial resistivity surveys be collected before GPR and ERT follow-up surveys are collected over the identified geophysical anomalies.     

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.     

Soilwater Conductivity Analysis to Date and Locate Clandestine Graves of Homicide Victims

In homicide investigations, it is critically important that postmortem interval and postburial interval (PBI) of buried victims are determined accurately. However, clandestine graves can be difficult to locate; and the detection rates for a variety of search methods (ranging from simple ground probing through to remote imaging and near‐surface geophysics) can be very low. In this study, simulated graves of homicide victims were emplaced in three sites with contrasting soil types, bedrock, and depositional environments. The long‐term monthly in situ monitoring of grave soil water revealed rapid increases in conductivity up to 2 years after burial, with the longest study evidencing declining values to background levels after 4.25 years. Results were corrected for site temperatures and rainfall to produce generic models of fluid conductivity as a function of time. The research suggests soilwater conductivity can give reliable PBI estimates for clandestine burials and therefore be used as a grave detection method.     

Sequential monitoring of burials containing small pig cadavers using ground penetrating radar

Ground-penetrating radar (GPR) was used to monitor 12 pig burials in Florida, each of which contained a small pig cadaver. Six of the cadavers were buried in sand at a depth of 0.50-0.60 m, and the other six were buried in sand at a depth of 1.00-1.10 m to represent deep and shallow burials that are generally encountered in forensic scenarios. Four control excavations with no pig interment were also constructed as blank graves and monitored with GPR. The burials were monitored for durations of either 13 or 21 months, and were then excavated to correlate the decomposition state of the cadaver with the GPR imagery. Overall, this study demonstrated that it may be difficult to detect small cadavers buried in sand soon after they are skeletonized because the area surrounding the body, or the grave, may not provide a strong enough contrasting area to be detected by GPR when compared to that of the surrounding undisturbed soil. Also, depth of burial appears to influence grave detection because bodies that are buried at deeper depths may be detected for a longer period of time due to reduced decomposition rates.     

Soil Fungi: Their Potential use as a Forensic Tool

As a grave is an anomalous environment and differs from its surroundings, criminal investigators employ different techniques for locating, recovering, and analyzing clandestine graves. In this study were identified the fungi found in the soil under corpses in decomposition with an aim at relating the copresence of human remains and different fungal species. Were isolated the fungi in three ways: soil washing, serial dilutions, and moist chamber growth. Dichotomomyces cejpii, Talaromyces trachyspermus, Talaromyces flavus, and Talaromyces sp. were the representative species found—with those belonging to the ammonia group, whose fungi are the first in the succession of cadaver decomposition directly in the ground. The mycobiota found at the present study area clearly differs to mycobiota identified in control sample and from previously described species for other areas of Buenos Aires Province, Argentina. Further forensic examples of this type are needed to develop fully the detailed use of mycology as a forensic tool.     

Mites (Acari) as a Relevant Tool in Trace Evidence and Postmortem Analyses of Buried Corpses

This report interprets the presence of mite species in three clandestine graves in Europe, evaluating their potential use as trace evidence or markers. Grave 1 (Sweden): Two mite species Rhizoglyphus robini Claparède, 1869 and Parasitus loricatus (Wankel, 1861) were recovered from the surface of a body buried in a shallow grave in an area surrounded by trees, in close vicinity to house gardens. Grave 2 (Germany): Phoretic deutonymphs of Gamasodes spiniger (Trägårdh, 1910) were attached to an adult fly (Diptera: Sphaeroceridae) found within a shallow grave containing two human bodies covered in soil and dung. Grave 3 (France): P. loricatus were recovered from the soil around a body buried in a deep grave (80 cm under). In graves 1 and 3 both corpses were undergoing advanced decay and skeletization, the locations match with the subterranean habit of P. loricatus, highlighting the value of this species as a marker of graves or burials in soil and during late decomposition. R. robini is a soil mite that feeds on decayed roots and bulbs; this mite species confirms the location of the corpse within top soil, agreeing with a more specific type of superficial burial, a shallow grave. In case 2, the presence of both coprophiles, the mite G. spiniger and the carrier fly confirm association of remains with dung or animal feces. The three mite species are reported for the first time in human graves. There are no previous records of R. robini from Sweden.     

The detection of clandestine graves in an arid environment using thermal imaging deployed from an unmanned aerial vehicle

The Middle East is one of the world regions that has frequently suffered from armed conflicts that resulted in mass burials. However, the detection of clandestine graves in such an arid environment by deploying remote sensing payload on unmanned aerial vehicles (UAVs) has received little attention. The present study used a UAV equipped with a thermal sensor aimed at narrowing down the search area of possible gravesites in the arid climate of Kuwait. The enclosed research area, which includes both control and experimental mass graves, was imaged for 18 months. The variation in topsoil temperature and soil moisture between the graves and their surroundings was evaluated. The results of the analysis demonstrated the effectiveness of thermal imaging techniques in detecting heat produced from buried sheep carcasses and detecting the change in grave soil moisture for our research environment for 7 and 10 months, respectively. The buried animals significantly influenced the topsoil temperature (p = 0.044), while the height from which the images were captured had an insignificant effect on the measured temperature within the range tested (p = 0.985). Furthermore, there was a negative correlation (−0.359) between grave temperature and the calculated soil moisture. The results from these cost- and time-effective search methods presented in this study confirm their potential for the detection of burial sites in an arid environment.     

Taphonomic mycota: fungi with forensic potential

Forensic archaeologists and criminal investigators employ many different techniques for the location, recovery, and analysis of clandestine graves. Many of these techniques are based upon the premise that a grave is an anomaly and therefore differs physically, biologically, or chemically from its surroundings. The work reviewed in this communication demonstrates how and why field mycology might provide a further tool towards the investigation of scenes of crime concealed in forest ecosystems. The fruiting structures of certain fungi, the ammonia and the postputrefaction fungi, have been recorded repeatedly in association with decomposed mammalian cadavers in disparate regions of the world. The ecology and physiology of these fungi are reviewed briefly with a view to their potential as a forensic tool. This application of mycology is at an interface with forensic archaeology and forensic taphonomy and may provide a means to detect graves and has the potential to estimate postburial interval.     

Decompositional odor analysis database

This study, conducted at the University of Tennessee's Anthropological Research Facility (ARF), describes the establishment of the Decompositional Odor Analysis (DOA) Database for the purpose of developing a man-portable, chemical sensor capable of detecting clandestine burial sites of human remains, thereby mimicking canine olfaction. This "living" database currently spans the first year and a half of burial, providing identification, chemical trends and semi-quantitation of chemicals liberated below, above and at the surface of graves 1.5 to 3.5 ft deep (0.45 to 1.0 m) for four individuals. Triple sorbent traps (TSTs) were used to collect air samples in the field and revealed eight major classes of chemicals containing 424 specific volatile compounds associated with burial decomposition. This research is the first step toward identification of an "odor signature" unique to human decomposition with projected ramifications on cadaver dog training procedures and in the development of field portable analytical instruments which can be used to locate human remains buried in shallow graves.     

Testing Application of Geographical Information Systems,Forensic Geomorphology and Electrical Resistivity Tomography to Investigate Clandestine Grave Sites in Colombia,South America

Colombian forensic investigators required assistance locating clandestine burials of missing persons related to human right atrocities from 14 years ago. Geoscientific search methods were trialled, including a predictive spatial statistical model, using various input and database information, to select the most likely grave locations in difficult mountainous terrain. Groundwork using forensic geomorphology, near-surface geophysics (ERT) and subsequent probing identified suspect burial positions. One site was in mountainous terrain and the other in former school grounds, both difficult to access and in poor weather conditions. In the mountainous area, a negative resistivity anomaly area was identified and intrusively investigated, found to be a buried rock. In school grounds, after MESP and intelligence were used to identify a burial site, surface depressions were identified, and ERT datasets collected over the highest priority depression; intrusive investigations discovered a hand-dug pit containing animal bones. This approach is suggested for Latin American searches.     

Vegetation dynamics as a tool for detecting clandestine graves

The burial of a body can affect plant communities through mechanical disturbance and nutrient balance alteration. We performed an experimental trial using five swine carcasses buried in an open site in Italy. Vegetation dynamics was monitored recording monthly every plant individual on a regular sampling grid during 1 year on the graves, on an empty control grave, and on an undisturbed plot. Plant species composition and cover were significantly different between the disturbed and the undisturbed plots. Disturbed plots showed the increase in ruderal species and the reduction in stress-tolerant ones. Graves and the control grave could not be distinguished from each other. Disturbance was the main factor affecting plant cover, while the presence of a buried body did not affect vegetation dynamics. However, disturbance could be easily detected; the functional approach seems promising for the identification of dynamic patterns to be used in different biogeographic and ecological contexts.     

Effects of hydrated lime and quicklime on the decay of buried human remains using pig cadavers as human body analogues

Recent casework in Belgium involving the search for human remains buried with lime, demonstrated the need for more detailed understanding of the effect of different types of lime on cadaver decomposition and its micro-environment. Six pigs (Sus scrofa) were used as body analogues in field experiments. They were buried without lime, with hydrated lime (Ca(OH)(2)) and with quicklime (CaO) in shallow graves in sandy loam soil in Belgium and recovered after 6 months of burial. Observations from these field recoveries informed additional laboratory experiments that were undertaken at the University of Bradford, UK. The combined results of these studies demonstrate that despite conflicting evidence in the literature, hydrated lime and quicklime both delay the decay of the carcass during the first 6 months. This study has implications for the investigation of clandestine burials and for a better understanding of archaeological plaster burials. Knowledge of the effects of lime on decomposition processes also has bearing on practices involving burial of animal carcasses and potentially the management of mass graves and mass disasters by humanitarian organisations and DVI teams.     

Using ninhydrin to detect gravesoil

Some death scene investigations commence without knowledge of the location of the body and/or decomposition site. In these cases, it is necessary to locate the remains or the site where the body decomposed prior to movement. We hypothesized that the burial of a mammalian cadaver will result in the release of ninhydrin reactive nitrogen (NRN) into associated soil and that this reaction might have potential as a tool for the identification of clandestine graves. Juvenile rat (Rattus rattus) cadavers were buried in three contrasting soil types in Australian tropical savanna ecosystems and allowed to decompose over a period of 28 days. Soils were sequentially harvested and analyzed for NRN. Cadaver burial resulted in an approximate doubling (mean = 1.7 +/- 0.1) in the concentration of soil NRN. This reaction has great potential to be used as a presumptive test for gravesoil and this use might be greatly enhanced following more detailed research.     

Experimental validation of forensic evidence: a study of the decomposition of buried pigs in a heavy clay soil.

In a murder investigation, where the victim had been strangled and buried in a shallow grave, there were discrepancies between the post mortem interval (PMI) as estimated from entomological studies and estimations determined from other evidence. This inconsistency provided the impetus for examining the decay process using pig carcasses as analogues for the human cadaver. The pigs were buried in the immediate vicinity of the original burial site in December 1996, which was the month when the victim was purported to have been interred in the previous year. The buried pigs were then monitored for 5 months which, based on the evidence other than the entomological, was the period over which the corpse was thought to have lain in the ground. The pig corpses were disturbed by scavengers in mid April: this was the same time that the human corpse was discovered in the previous year by scavengers. Insects played no role in the decomposition process until the pig carcasses had been exposed by animals. Blowflies, notably Calliphora vomitoria, were attracted to the exposed tissues and laid eggs from which larvae developed. Calliphora vomitoria is a species often used to estimate PMI. This investigation has shown that soil conditions and low seasonal temperatures had preserved the pig carcasses for longer than might be expected. Using the blowfly larvae to estimate PMI would have produced erroneous results had not the burial environment and exhumation history been investigated.     

Sequential monitoring of burials containing large pig cadavers using ground-penetrating radar

Ground-penetrating radar (GPR) was used to monitor 12 pig burials in Florida, each of which contained a large pig cadaver. Six of the cadavers were buried in sand at a depth of 0.50-0.60 m, and the other six were buried at a depth of 1.00-1.10 m and were in contact with the upper surface of a clay horizon. Control excavations with no pig internment were also constructed as blank graves and monitored with GPR. The burials were monitored with GPR for durations of either 12-13 or 21-21.5 months when they were then excavated to correlate the decomposition state of the cadaver with the GPR imagery. Overall, cadavers in sand were easily detected for the duration of this study at 21.5 months, even when completely skeletonized. Conversely, in clay it became increasingly difficult to image the pig cadavers over the first year of burial, even when they still retained extensive soft tissue structures.     

Graves and families in Japan: Continuity and change

The population aging in Japan has been accelerated not only by the nation's longest life expectancy at birth but also by its falling fertility rate. As the existence of a Japanese family's grave presupposes the continuity of the family line, Japan's current low fertility rate has increased families without progeny who now face problems of their family graves becoming “disconnected.” In this study, historical trends of graves in Japan were analyzed — how the idea of traditional family grave was socially constructed and how it has transformed society, culture, and families. In addition, analyzing the Japanese General Social Survey (JGSS) 2001, it addresses the importance of gender on people's expectations about burial partners in current Japanese society. The analysis of JGSS-2001 data revealed that although the majority of people chose graves with succession across generations, younger generations were more likely to support diversified graves than were older generations, and this difference was greater for women than for men. Finally, understanding problems and limitations of current Japanese graves, future issues of Japanese graves will be addressed.