A Preliminary Examination of Differential Decomposition Patterns in Mass Graves

Five pairs of mass graves, each containing carcasses of 21 rabbits, were used to examine differential decomposition at four locations within the burial: surface, deep, mid‐outer, and core. Every 100 accumulated degree days (ADD), a pair of graves was exhumed, and total body score (TBS) and internal carcass temperature of each rabbit were recorded. Decomposition did not differ for core‐ and deep‐positioned carcasses (p = 0.13); differences were significant (p < 0.001) for all other location comparisons. Decomposition occurred fastest in shallow carcasses, followed by mid‐outer carcasses; deep and core carcasses decomposed slowest and at rates not significantly different from one another. Adipocere formation was minimal and confined to deep carcasses. Carcass location within the mass grave significantly influenced internal carcass temperature (p < 0.001); a mean internal temperature difference of ca. 1°C existed between deep and shallow carcasses (30 cm apart). Effects of mass compactness and oxygenation require further investigation.     

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.     

Preliminary Observations of Arthropods Associated with Buried Carrion on Oahu

Several studies in Hawaii have focused on arthropod succession and decomposition patterns of surface remains, but the current research presents the first study to focus on shallow burials in this context. Three domestic pig carcasses (Sus scrofa L.) were buried at the depths of 20–40 cm in silty clay loam soil on an exposed ridge on the leeward side of the volcanically formed Koolau Mountain Range. One carcass was exhumed after 3 weeks, another after 6 weeks, and the last carcass was exhumed after 9 weeks. An inventory of arthropod taxa present on the carrion and in the surrounding soil and observations pertaining to decomposition were recorded at each exhumation. The longer the carrion was buried, the greater the diversity of arthropod species that were recovered from the remains. Biomass loss was calculated to be 49% at the 3‐week interval, 56% at the 6‐week interval, and 59% at the 9‐week interval.     

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.     

Keeping the pieces together: comparison of mass grave excavation methodology

Mass graves are a complex and confusing mix of bodies, body parts, soils, artifacts, and other feature evidence. Forensic investigations of these complex crime scenes should attempt to maximize the collection of evidence, which includes the mortal remains, in their best possible condition as they were deposited within the graves. Two standard methods of mass grave excavation were examined with the aim of identifying the better approach. Two experienced teams using different methodologies excavated two separate but very comparable mass graves located in the same area. Single disarticulated skeletal elements not associated with a body at the time of removal from the grave were categorized and their counts analyzed to evaluate the efficiency of the differing excavation methodologies. The methodologies used were the 'pedestal' method, which focuses on the body mass, and the 'stratigraphic' method, in which the grave feature and contents are conjointly excavated. The first grave (Grave A), excavated using the 'pedestal' method, was observed to have a disproportionately larger amount of unassociated bones than did the second (Grave B), which used the 'stratigraphic' method. Chi-square (chi2) goodness-of-fit and contingency tests were performed on the total numbers of recorded elements and different categorical groups of bones, based on size and shape, in each grave. Results demonstrate that significantly greater numbers of unassociated elements resulted from the excavation of Grave A using the pedestal method, both in total number of disarticulated bones as well as within 'large' and 'medium' categories. Conversely 'small' skeletal elements were recovered at a higher rate in Grave B. The lower 'large' and 'medium' bone production rates from Grave B indicate that the stratigraphic method better maintained the provenience and articulation of remains than did Grave A, while the higher 'small' bone recovery rate may point to better recovery techniques of Grave B's excavation team.     

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.     

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.     

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.     

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 Effects of Soil Texture on the Ability of Human Remains Detection Dogs to Detect Buried Human Remains

Despite technological advances, human remains detection (HRD) dogs still remain one of the best tools for locating clandestine graves. However, soil texture may affect the escape of decomposition gases and therefore the effectiveness of HDR dogs. Six nationally credentialed HRD dogs (three HRD only and three cross‐trained) were evaluated on novel buried human remains in contrasting soils, a clayey and a sandy soil. Search time and accuracy were compared for the clayey soil and sandy soil to assess odor location difficulty. Sandy soil (p < 0.001) yielded significantly faster trained response times, but no significant differences were found in performance accuracy between soil textures or training method. Results indicate soil texture may be significant factor in odor detection difficulty. Prior knowledge of soil texture and moisture may be useful for search management and planning. Appropriate adjustments to search segment sizes, sweep widths and search time allotment depending on soil texture may optimize successful detection.     

An investigation into the effects of decomposition on the post-mortem location of trans-dermal artefacts

A search area of a crime scene to recover trans-dermal artefacts (here, earrings) was conducted using 12 pig carcasses, of various sizes, with pierced ears; 6 were buried and 6 deposited on the surface in a wooded area. After 28 months, the remains were excavated and recovered, and the final location of the earrings recorded. The furthest recorded earring from its associated surface remains was 119 cm. In the buried remains, on three occasions earrings were found located 6 cm below the recorded base of the grave. Formal recommendations for the search area of a crime scene have been established as 120 cm radius from the originally located remains, whether surface deposition or burial, and confirmation of excavation below the assumed floor of the grave in burials is essential, at least to 10 cm.     

The Influence of Preburial Insect Access on the Decomposition Rate

Abstract: This study compared total body score (TBS) in buried remains (35 cm depth) with and without insect access prior to burial. Sixty rabbit carcasses were exhumed at 50 accumulated degree day (ADD) intervals. Weight loss, TBS, intra‐abdominal decomposition, carcass/soil interface temperature, and below‐carcass soil pH were recorded and analyzed. Results showed significant differences (p << 0.001) in decomposition rates between carcasses with and without insect access prior to burial. An approximately 30% enhanced decomposition rate with insects was observed. TBS was the most valid tool in postmortem interval (PMI) estimation. All other variables showed only weak relationships to decomposition stages, adding little value to PMI estimation. Although progress in estimating the PMI for surface remains has been made, no previous studies have accomplished this for buried remains. This study builds a framework to which further comparable studies can contribute, to produce predictive models for PMI estimation in buried human remains.     

The Influence of Insects on Decomposition Rate in Buried and Surface Remains

Abstract: This article reports results of a comparative study of decomposition rates of wild rabbit (Oryctolagus cuniculus) which were either (i) buried after exposure to insect activity, (ii) buried without exposure, (iii) kept above ground behind an insect screen, or (iv) continuously exposed above ground in a field experiment. Results showed that dipteran oviposition occurred consistently in groups i and iv only. Decomposition rates (measured by Total Body Score every c. 50 accumulated degree days [ADD]) of rabbits kept behind the screen and those buried without exposure showed no difference (p = 0.450). This was significantly slower than those buried after exposure (p = 0.0016) which was in turn significantly slower than those continuously exposed (p << 0.001). Temperatures collected from animals showed the presence of feeding larvae increased intra‐abdominal temperatures to >5°C above ambient. The findings support the assertion that insect presence is the primary agent affecting decomposition rate via tissue consumption and also the heat they generate.     

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.     

Shells and Bones: A Forensic Medicine Study of the Association of Terrestrial Snail Allopeas micra with Buried Human Remains in Brazil

Little is known regarding the scavenger fauna associated with buried human corpses, particularly in clandestine burials. We report the presence of 20 shells of the terrestrial snail Allopeas micra, within hollow bones of human remains buried for 5 years, during the process of collecting DNA material. The fact that a large number of shells of A. micra had been found in the corpse and in the crime scene supports the assumption that there was no attempt to remove the corpse from the area where the crime occurred. Despite this, our observations cannot be used to estimate the postmortem interval because there is no precise knowledge about the development of this species. This is the first record of a terrestrial snail associated with a human corpse and its role in this forensic medicine case.     

A Preliminary Forensic Entomological Study of Beetles (Coleoptera) in Interior Alaska,USA*

Forensic entomology uses knowledge of arthropod ecology to help solve crimes. There has been no published forensic entomological research in Alaska. We used one piglet carcass split in half to create two carcass plots in Fairbanks (~64.8°N, subarctic) that were sampled over a period of 59 days in 2019. Four pitfall traps were placed around each carcass, and four similarly arranged pitfall traps were placed 40 m distant as controls. Traps were emptied approximately weekly covering the first four stages of decomposition. We focused on adults of the larger-bodied (>9 mm) families and subfamilies of Coleoptera: Staphylinidae (subfamily Staphylininae), Carabidae, and Silphidae. A total of 621 specimens were collected and processed: 29 staphylinines, 210 carabids, and 382 silphids. A one-way ANOVA showed no significant difference between the mean numbers of staphylinines or carabids caught in carcass versus control traps. Silphids showed significantly greater mean number of beetles caught in carcass traps relative to control traps. Four species of Silphidae were documented, but contrary to similar studies, the vast majority of specimens belonged to two species of Nicrophorus (N. vespilloides Herbst and N. investigator Zetterstedt). Each of the three target taxa showed a peak in the number of specimens collected during the bloat stage of decomposition despite the carabid peak being driven by a phytophagous species.     

Estimating postmortem interval for human cadavers in a sub‐tropical climate using UV‐Vis‐near‐infrared Spectroscopy

Estimating postmortem interval (PMI) of surface found skeletal remains is challenging. This novel study used UV‐Vis‐NIR spectroscopy to scan soil collected from cadaver decomposition islands (CDIs) ranging from 15‐ to 963‐d postmortem and control soils. A decomposition product spectra model (DPS model) was constructed by deducting the control soil spectra from the CDI soil spectra for the estimation of postmortem indices: PMI (d), ADD₄, ADD₁₀, and ADD₂₀. The DPS model (n = 55) was calibrated and subjected to a full cross‐validation. Calibration R² and RPD for the DPS model ranged from 0.97 to 0.99 and from 6.1 to 9.9, respectively, for the four postmortem interval indices. Validation R² and RPD for the DPS model ranged from 0.73 to 0.80 and from 1.9 to 2.2, respectively. The DPS model estimated postmortem intervals for three test CDIs in a clay soil under perennial grassland (test set 1; n = 3) and six CDIs in a sandy soil under a loblolly pine forest (test set 2; n = 6). Test set 1 had PMI prediction ranges from ?69 to ?117 days, ?796 to +832 ADD₄, +552 to +2672 ADD₁₀, and ?478 to ?20 ADD₂₀ of observed PMI. Test set 2 PMI prediction ranged from ?198 to ?65 days, ?9923 to +2629 ADD₄, ?6724 to +1321 ADD₁₀, and ?2850 to +540 ADD₂₀ of observed PMI. Test set 2 had poor predictions for two CDIs, for all measures of postmortem indices resulting in discussion of sampling depth, effect of body mass index (BMI), and scavenging.     

Identification of Crystals Forming on Porcine Articular Cartilage: A New Method for the Estimation of the Postmortem Interval

Articular cartilage was examined to determine its decomposition sequence and its potential for assessing the postmortem interval. Scanning electron microscopy of articular cartilage from buried porcine trotters showed the presence of microcrystals on the synovial surface. These orthorhombic pyramidal or “coffin”‐shaped crystals, appeared at 3 weeks (22 days) after interment and disappeared after 6 weeks. The disappearance of these crystals was linked to decompositional changes to the integrity of the synovial joint. The formation and disappearance of these crystals was associated with a pH change at the cartilage surface. Scanning electron microscopy–energy‐dispersive X‐ray (SEM‐EDX) analysis showed that the five main elements contained within these crystals were carbon, nitrogen, oxygen, magnesium, and phosphorous. Such elemental analysis suggested the crystals may be struvite (MgNH₄PO₄6(H₂O)). Bacteria cultured from the cartilage synovial surface produced struvite crystals when grown in suitable media and were identified by DNA analysis to be Comamonas sp.     

The Effect of Clothing on the Rate of Decomposition and Diptera Colonization on Sus scrofa Carcasses

Twenty Sus scrofa carcasses were used to study the effect the presence of clothing had on decomposition rate and colonization locations of Diptera species; 10 unclothed control carcasses were compared to 10 clothed experimental carcasses over 58 days. Data collection occurred at regular accumulated degree day intervals; the level of decomposition as Total Body Score (TBS_surf), pattern of decomposition, and Diptera present was documented. Results indicated a statistically significant difference in the rate of decomposition, (t₄₂₇ = 2.59, p = 0.010), with unclothed carcasses decomposing faster than clothed carcasses. However, the overall decomposition rates from each carcass group are too similar to separate when applying a 95% CI, which means that, although statistically significant, from a practical forensic point of view they are not sufficiently dissimilar as to warrant the application of different formulae to estimate the postmortem interval. Further results demonstrated clothing provided blow flies with additional colonization locations.