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.     

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.     

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.     

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.     

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.     

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.     

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.     

Cytochrome b based genetic differentiation of Indian wild pig (Sus scrofa cristatus) and domestic pig (Sus scrofa domestica) and its use in wildlife forensics

The Indian wild pig (Sus scrofa cristatus) is a protected species and listed in the Indian Wildlife (Protection) Act, 1972. The wild pig is often hunted illegally and sold in market as meat warranting punishment under law. To avoid confusion in identification of these two subspecies during wildlife forensic examinations, we describe genetic differentiation of Indian wild and domestic pigs using a molecular technique. Analysis of sequence generated from the partial fragment (421 bp) of mitochondrial DNA (mtDNA) cytochrome b (Cyt b) gene exhibited unambiguous (> 3%) genetic variation between Indian wild and domestic pigs. We observed nine forensically informative nucleotide sequence (FINS) variations between Indian wild and domestic pigs. The overall genetic variation described in this study is helpful in forensic identification of the biological samples of wild and domestic pigs. It also helped in differentiating the Indian wild pig from other wild pig races. This study indicates that domestic pigs in India are not descendent of the Indian wild pig, however; they are closer to the other wild pig races found in Asia and Europe.     

Testing the Use of Pigs as Human Proxies in Decomposition Studies

Pigs are a common human analogue in taphonomic study, yet data comparing the trajectory of decomposition between the two groups are lacking. This study compared decomposition rate and gross tissue change in 17 pigs and 22 human remains placed in the Forensic Investigation Research Station in western Colorado between 2012 and 2015. Accumulated degree days (ADD) were used to assess the number of thermal units required to reach a given total body score (TBS) (1) which was used as the measure of decomposition. A comparison of slopes in linear mixed effects model indicated that decomposition rates significantly differed between human donors and pig remains χ²₍₁₎ = 5.662, p = 0.017. Neither the pig nor the human trajectory compared well to the TBS model. Thus, (i) pigs are not an adequate proxy for human decomposition studies, and (ii) in the semiarid environment of western Colorado, there is a need to develop a regional decomposition model.     

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.     

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.     

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.     

Animal Scavenging and Scattering and the Implications for Documenting the Deaths of Undocumented Border Crossers in the Sonoran Desert,

Since 1998, over 5500 people have died while attempting to cross the U.S.–Mexico border without authorization. These deaths have primarily occured in the Arizona desert. Despite the high volume of deaths, little experimental work has been conducted on Sonoran Desert taphonomy. In this study, pig carcasses were used as proxies for human remains and placed in different depositional contexts (i.e., direct sunlight and shade) that replicate typical sites of migrant death. Decomposition was documented through daily site visits, motion-sensitive cameras and GIS mapping, while skeletal preservation was investigated through the collection of the remains and subsequent faunal analysis. Our results suggest that vultures and domestic dogs are underappreciated members of the Sonoran scavenging guild and may disperse skeletal remains and migrant possessions over 25 m from the site of death. The impact of scavengers and the desert environment on the decomposition process has significant implications for estimating death rates and identifying human remains along the Arizona/Mexico border.     

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.     

Multi-agent scavenging patterns in Hawai‘i: A forensic archaeological and skeletal case study

Knowledge of the behavior of local fauna can aid forensic investigators in developing awareness of site formation processes. In Hawai‘i, little has been published on the effects of feral domestic pig (Sus scrofa) and feral domestic dog (Canis familiaris) scavenging and bone dispersal on field recovery and laboratory observations. In this Pacific tropical setting, the most consequential terrestrial taphonomic agents are pigs and dogs, both in terms of hard tissue modification and dispersal of remains across the landscape. In 2017, an archaeologist discovered the remains of an unidentified decedent on the island of Kauaʻi, State of Hawai‘i during a cultural resource management survey. Subsequently, a forensic recovery team in conjunction with Kaua‘i police and crime scene investigators used archaeological techniques, including pedestrian survey, tape-and-compass, and GPS mapping, to map and recover the remains. A feral pig trail transected various areas of the recovery site and corresponded with the distribution pattern of recovered skeletal material, including both the main concentration more broadly dispersed skeletal elements. While much of the skeleton was present, missing or unrecovered skeletal elements are consistent with expectations based on existing literature. Much of the postmortem bone deformations were characteristic of marks related to feral dog and/or feral pig scavenging. These results assisted local investigators in deciding the manner of death, as well as providing the family with an accounting of the decedent’s remains for burial. Thus, forensic anthropologists and archaeologists need to understand and develop knowledge of local animal behavior to recover and interpret human remains of medicolegal significance.     

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.     

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.     

Characterization of the volatile organic compounds present in the headspace of decomposing animal remains, and compared with human remains

Human Remains Detection (HRD) dogs can be a useful tool to locate buried human remains because they rely on olfactory rather than visual cues. Trained specifically to locate deceased humans, it is widely believed that HRD dogs can differentiate animal remains from human remains. This study analyzed the volatile organic compounds (VOCs) present in the headspace above partially decomposed animal tissue samples and directly compared them with results published from human tissues using established solid-phase microextraction (SPME) and gas chromatography/mass spectrometry (GC/MS) methods. Volatile organic compounds present in the headspace of four different animal tissue samples (bone, muscle, fat and skin) from each of cow, pig and chicken were identified and compared to published results from human samples. Although there were compounds common to both animal and human remains, the VOC signatures of each of the animal remains differed from those of humans. Of particular interest was the difference between pigs and humans, because in some countries HRD dogs are trained on pig remains rather than human remains. Pig VOC signatures were not found to be a subset of human; in addition to sharing only seven of thirty human-specific compounds, an additional nine unique VOCs were recorded from pig samples which were not present in human samples. The VOC signatures from chicken and human samples were most similar sharing the most compounds of the animals studied. Identifying VOCs that are unique to humans may be useful to develop human-specific training aids for HRD canines, and may eventually lead to an instrument that can detect clandestine human burial sites.     

The Initial Changes of Fat Deposits During the Decomposition of Human and Pig Remains

Abstract:  The early stages of adipocere formation in both pig and human adipose tissue in aqueous environments have been investigated. The aims were to determine the short-term changes occurring to fat deposits during decomposition and to ascertain the suitability of pigs as models for human decomposition. Subcutaneous adipose tissue from both species after immersion in distilled water for up to six months was compared using Fourier transform infrared spectroscopy, gas chromatography-mass spectrometry and inductively coupled plasma-mass spectrometry. Changes associated with decomposition were observed, but no adipocere was formed during the initial month of decomposition for either tissue type. Early-stage adipocere formation in pig samples during later months was detected. The variable time courses for adipose tissue decomposition were attributed to differences in the distribution of total fatty acids between species. Variations in the amount of sodium, potassium, calcium, and magnesium were also detected between species. The study shows that differences in total fatty acid composition between species need to be considered when interpreting results from experimental decomposition studies using pigs as human body analogs.