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.     

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.     

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.     

The Search for “Fred”: An Unusual Vertical Burial Case,

Police witness intelligence stated a murdered adult male “Fred” had been vertically buried in wooded hilly terrain 30 years ago in the Midlands, U.K. Conventional search methods were unsuccessful; therefore, the police requested a geophysical investigation to be undertaken to determine whether “Fred” could be detected. A multiphased geophysical approach was conducted, using bulk ground conductivity and metal detectors, then follow‐up magnetics and ground penetrating radar (GPR) survey profiles on electromagnetic (EM) anomalous areas. A tight grid pattern was used to account for the reduced target size. Relatively high‐resolution EM and GPR techniques were determined optimal for this terrain and sandy soil. Geophysical anomalies were identified and the most promising intrusively investigated, and this was found to be a large boulder and tree roots. Study implications suggest careful multiphase geophysical surveys are best practice and give confidence in cold case searches. This study yielded a no‐body result, effectively saving police time and costs from further investigations.     

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.     

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.     

Time-lapse resistivity surveys over simulated clandestine graves

The aim of this study was to develop a better understanding of how electrical resistivity surveys can be used to locate clandestine graves. Resistivity surveys were conducted regularly over three simulated clandestine graves containing a pig cadaver, no cadaver and a pig cadaver wrapped in tarpaulin, respectively. Additionally, soil and groundwater samples were collected from two more simulated graves outside the survey area. The grave containing a pig cadaver was detectable from a low resistivity anomaly in the survey data. Groundwater data suggest that the resistivity anomaly associated with the surveyed pig grave was caused by a localised increase in groundwater conductivity. Wrapping a cadaver was found to initially change the resistivity response of a grave to a high resistivity anomaly. Resistivity surveys did not detect the disturbed soil in the grave that did not contain a cadaver. Although soil samples showed grave soil to be more porous than undisturbed soil, the lack of response from the grave that did not contain a cadaver suggests that disturbed soil was not responsible for the resistivity anomalies observed in this study. Resistivity surveys successfully detected all graves containing cadavers throughout the study, whilst also showing the potential to eliminate the need for mass excavation in a genuine search.     

Ground penetrating radar surveys to locate 1918 Spanish flu victims in permafrost

The "Spanish Flu" killed over 40 million people worldwide in 1918. Archival records helped us identify seven men who died of influenza in 1918 and were interred in Longyearbyen, Svalbard, Norway, 1,300 km from the North Pole. Ground Penetrating Radar (GPR) was used successfully, in a high-resolution field survey mode, to locate a large excavation with seven coffins, near the existing seven grave markers. The GPR indicated that the ground was disturbed to 2 m depth and was frozen below 1 m. Subsequent excavation showed that: a) the GPR located the position of the graves accurately, b) the coffins were buried less than 1 m deep, and c) that the frozen ground was 1.2 m deep where the coffins were located. The GPR assisted in planning the exhumation, safely and economically, under the high degree of containment required. Virologic and bacteriologic investigations on recovered tissues may give us an opportunity to isolate and identify the micro-organisms involved in the 1918 influenza and expand our knowledge on the pathogenesis of influenza.     

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.     

A clandestine burial in Costa Rica: prospection and excavation

Abstract:  This case report describes the search for a clandestine grave in Costa Rica for which the police sought the assistance of an archaeologist. An anonymous informant suggested that the victim had been kidnapped and murdered, placed in a shallow grave in the woods, then covered with lime and cement. A search of the area to detect conventional signs of burial (e.g., slumping, different plant growth) resulted in excavation of unrelated features of past disturbance. Different aspects of the grave including the deposition of cement powder over the body prevented its initial discovery. Improvisation of conventional archaeological excavation methods and use of police familiar with archaeological excavation resulted in the location of the grave and exhumation of the victim without loss of important contextual evidence that supported testimony on the cause of death. The taphonomic effects of high-lying ground water and lime in the tropical burial environment are briefly discussed. Recommendations such as the construction of a temporary sump to lower the ground water level in the grave during excavation are made to assist in similar investigations in the future.     

The search for "Yvonne": a case example of the delineation of a grave using near-surface geophysical methods

Shallow electromagnetic (EM) and ground-penetrating radar (GPR) surveys were conducted in an area north of Auckland, New Zealand to assist the search for human remains. The body had been buried for almost 12 years in a plantation forest that was irregularly disrupted and modified by tree harvesting and the partial removal of stumps. EM identified anomalous areas of potential interest, because a target need only be nearby to generate an EM response. GPR was then used to map subsurface layering, layering disruption, and buried objects, immediately adjacent to an EM anomaly. Because of the nature of the site, numerous geophysical anomalies were present. GPR was particularly sensitive to site disturbance resulting from the forestry operations. An isolated EM anomaly on the fringes of an expanded survey area was coincident with the location of the body. Whether for criminal investigations or for archaeological work, a combination of geophysical techniques is recommended.     

Toolmark Identification of a Mattock to a Clod of Soil from a Grave

Abstract: At a recent bushland gravesite that contained a deceased male, a clod of soil displaying a striated toolmark was collected during the excavation of the grave. This clod was preserved, and the mark was cast using Mikrosil?. Shovels and a mattock, which had been discarded by the suspects, were subsequently found at another location. A toolmark comparison identified the hoe end of the mattock head as having produced the striated toolmark.     

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.     

Location and Assessment of an Historic (150–160 Years Old) Mass Grave Using Geographic and Ground Penetrating Radar Investigation,NW Ireland*

Abstract: Reburial of human remains and concerns regarding pathogens and pollution prompted the search for, and assessment of, a 156-year-old graveyard. To locate this graveyard, historic and anecdotal information was compared to landscape interpretation from aerial photography. To assess and map the contents, surface collapses, metal detector indications, and ground-penetrating radar (GPR) were used. Some 170 anomalies compatible with burials were identified on 200 MHz GPR data, 84 of which coincided with surface collapses, suggesting both noncollapsed ground, subsequent infill, and multiple inhumations. The graveyard was possibly split into Roman Catholic plots with multiple inhumations; Protestant plots; and a kileen, or graveyard for the unbaptized (often children). The work serves as one approach to the location and mapping of recent and historic unmarked graves.     

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.     

The Application of Remote Sensing for Detecting Mass Graves: An Experimental Animal Case Study from Costa Rica*

Abstract: Detection of mass graves utilizing the hyperspectral information in airborne or satellite imagery is an untested application of remote sensing technology. We examined the in situ spectral reflectance of an experimental animal mass grave in a tropical moist forest environment and compared it to an identically constructed false grave which was refilled with soil, but contained no cattle carcasses over the course of a 16‐month period. The separability of the in situ reflectance spectra was examined with a combination of feature selection and five different nonparametric pattern classifiers. We also scaled up the analysis to examine the spectral signature of the same experimental mass grave from an air‐borne hyperspectral image collected 1 month following burial. Our results indicate that at both scales (in situ and airborne), the experimental grave had a spectral signature that was distinct and therefore detectable from the false grave. In addition, we observed that vegetation regeneration was severely inhibited over the mass grave containing cattle carcasses for up to a period of 16 months. This experimental study has demonstrated the real utility of airborne hyperspectral imagery for the detection of a relatively small mass grave (5 m²) within a specific climatic zone. Other climatic zones will require similar actualistic modeling studies, but it is clear that the applications of this technology provide the international community with both an early detection tool and a tool for ongoing monitoring.     

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.     

Eristalinus arvorum (Fabricius, 1787) (Diptera: Syrphidae) in Human Skull: A New Fly Species of Forensic Importance

A body of an unknown adult female was found within a shallow burial ground in Malaysia whereas the skull was exposed and visible on the ground. During autopsy examination, nine insect larvae were recovered from the interior of the human skull and subsequently preserved in 70% ethanol. The larvae were greyish in appearance, each with a posterior elongated breathing tube. A week after the autopsy, more larvae were collected at the burial site, and some of them were reared into adults. Adult specimens and larvae from the skull and from the burial site were sequenced to obtain DNA barcodes. Results showed all adult flies reared from the burial site, as well as the larvae collected from the skull were identified as Eristalinus arvorum (Fabricius, 1787) (Diptera: Syrphidae). Here, we report the colonization of E. arvorum larvae on a human corpse for the first time.     

Suspect burial excavation procedure: A cautionary tale

Geographic location, time of reporting and need for rapid evaluation contributed to a lack of intelligence concerning a suspect burial site in scrub woodland (～15 km from the last known location of a missing person) in Northern Ireland. Police received reports of a subsiding ‘grave’, which was evaluated positively using GPR and victim recovery dogs (VRD). After 24 h work, archaeological excavation showed a vertical-sided, stepped excavation on undisturbed clay with no inhumation. Subsequent research showed the feature to be an engineering trial pit. The GPR response was a water table and rocks, VRD were possibly reacting to disturbed ground. The work serves as a demonstration of good archaeological practice in suspect burial excavation, following a lack of landscape evaluation and poor overall intelligence.     

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.