Clandestine Graves Research Articles

Making sense of clandestine graves: Material epistemology and the political geography of uncertain knowledge

How might we begin to establish meaning, understanding and justice out of something that is meant not to be found? In this article, we approach the growing problem of clandestine graves to ask what can be read from them, including why they matter, why they are found, and how they are becoming an intractable part of life for millions of citizens. Departing from the clandestine graves of São Paulo and Mexico, we argue that these material spaces are produced by ambiguous governance structures, and in turn reproduce them in ways that are unevenly knowable. The characteristics of these spaces that are otherwise shrouded in suspicion and deliberate efforts to make them unknowable reveal patterns and practices of political order while simultaneously creating certainty and fear about the governance they perpetuate. In taking the mass grave as an epistemology, we seek to establish identifiable tenents and patterns for further research and action while recognizing the challenges in asserting a knowledge claim about material spaces that are so intentionally, but unevenly, unknowable.

Applications of geoforensic trace evidence

Geoforensic trace evidence studies can be crucial for law enforcement and civil/criminal prosecution and defence, to test potential links between suspect(s), crime scenes or forensic object(s). In addition, trace geological evidence can be used to identify forensic sites of interest such as clandestine graves of murder victims. However, geoforensic trace evidence also has applications in a range of other investigations. This article briefly details the current geoscientific methods used to assist in such investigations and uses recent case studies to illustrate their use.

Assessing geospatial models to explain the occurrence of clandestine graves in Mexico

We present an assessment of several geospatial layers proposed as models for detecting clandestine graves in Mexico. The analyses were based on adapting the classical ROC curves to geospatial data (gROC) using the fraction of the predicted area instead of the false positive rate. Grave locations were obtained for ten Mexican states that represent the most conflicting regions in Mexico, and 30 layers were computed to represent geospatial models for grave detection. The gROC analysis confirmed that the travel time from urban streets to grave locations was the most critical variable for detecting graves, followed by nighttime light brightness and population density, whereas, contrary to the rationale, a previously proposed visibility index is less correlated with grave locations. We were also able to deduce which variables are most relevant in each state and to determine optimal thresholds for the selected variables.

A controlled method for the identification of forensic traces from clandestine grave fill

Deceased human remains are often buried as a forensic countermeasure or method of disposal by homicide perpetrators. Owing to this, the excavation of clandestine grave sites is a task that forensic crime scene teams may only encounter a few times a year. Not all crime scene units have specialised teams for this task, and even those that do, may not have specific protocols for the optimal recovery of forensic traces retained within grave fill as procedures such as sieving require optimisation for the specific soil conditions of the jurisdiction. This study aimed to define the optimal sieving conditions for a sandy environment when searching for minute traces of paint, glass, hair and fibres. Furthermore, this study justifies the practice of retaining grave fill and examining it under controlled laboratory conditions, rather than in-situ adjacent to the grave site. The results demonstrate that using sieve mesh sizes as fine as 0.1 mm can recover up to 82% of the deposited traces and almost all paint, hair and glass traces. The processing of grave fill in the laboratory lead to increased yield of forensic evidence, which on a case-basis may warrant the increased time needed. These findings merit consideration for clandestine grave crime scenes where evidence is scarce or the case is likely to become cold.

Monitoring of simulated clandestine graves of victims using UAVs, GPR, electrical tomography and conductivity over 4-8 years post-burial to aid forensic search investigators in Colombia, South America

In Colombia there are estimated to be over 121,000 missing people and victims of forced disappearances. Forensic investigators therefore need assistance in determining optimal detection techniques for buried victims, to give victims’ families closure and for the wider community to see that justice is being served. Previous research has created 12 controlled simulated clandestine graves of typical Colombian murder victim scenarios at 0.5 m – 1.2 m depths in savannah and rainforest sites in Colombia. The 0–3 years of geophysical monitoring results of were published, with this paper reporting on 4–8 years monitoring of both UAV drone results and geophysical data. The UAV results from the year 8 survey, published for first time from Colombia, showed that the simulated graves could still be located using NDVI and NIR multi-spectral data, but not using optical or other multi-spectral data. The 0–3 years of geophysical data found the simulated clandestine graves could be detected with electrical resistivity and GPR methods, with the 4–8 year surveys evidencing that they could still be detected using bulk ground conductivity surveys, GPR horizontal time slice datasets and 2D ERT profiles. Research implications suggest initial use of UAV remote sensing technology to pinpoint likely search areas, before subsequent ground reconnaissance, geophysical surveys and their interpretation, before intrusive investigation methods are employed for detecting missing and disappeared persons in Colombia.

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.

A technical protocol for using ground penetrating radar and electrical resistivity tomography in the search for covert graves

ABSTRACT The location of covert graves is an important but challenging part of missing persons investigations. Although traditional search techniques, such as foot searches and cadaver dogs, have proved successful, the incorporation of higher technology methods, such as geophysical techniques, can be used to increase the chances of locating covert graves. This article will present a field method for the use of two geophysical techniques, including ground penetrating radar and electrical resistivity tomography, which can successfully locate covert graves in an Australian environment. If the soil and climate conditions permit, this technical protocol can be applied to other clandestine grave search sites as well. Ultimately, by increasing chances of locating the covert grave, and by extension the missing person, a successful judicial outcome can be achieved and highly sought after answers can be provided to the family.

Utilizing Drone-Based Ground-Penetrating Radar for Crime Investigations in Localizing and Identifying Clandestine Graves.

The decomposition of a body is influenced by burial conditions, making it crucial to understand the impact of different conditions for accurate grave detection. Geophysical techniques using drones have gained popularity in locating clandestine graves, offering non-invasive methods for detecting surface and subsurface irregularities. Ground-penetrating radar (GPR) is an effective technology for identifying potential grave locations without disturbance. This research aimed to prototype a drone system integrating GPR to assist in grave localization and to develop software for data management. Initial experiments compared GPR with other technologies, demonstrating its valuable applicability. It is suitable for various decomposition stages and soil types, although certain soil compositions have limitations. The research used the DJI M600 Pro drone and a drone-based GPR system enhanced by the real-time kinematic (RTK) global positioning system (GPS) for precision and autonomy. Tests with simulated graves and cadavers validated the system's performance, evaluating optimal altitude, speed, and obstacle avoidance techniques. Furthermore, global and local planning algorithms ensured efficient and obstacle-free flight paths. The results highlighted the potential of the drone-based GPR system in locating clandestine graves while minimizing disturbance, contributing to the development of effective tools for forensic investigations and crime scene analysis.

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.

Winthropping as an Investigative Tool in Clandestine Grave Discovery and Psychological Profiling

Missing persons cases are some of the hardest investigations to solve. The lack of forensic evidence impedes an investigation and critical time can be lost attempting to find the person or body. Recently, researchers have attempted to develop new approaches to help police in these types of investigations. The current paper continues research into Winthropping as a means of assisting police investigations when searching for clandestine, hidden graves and missing persons. A novel approach, using geocachers, to help inform Winthropping processes is outlined, and support gained through a survey of geocachers. The findings are then applied to a series of real-world homicides, including several serial killers. Analyses of gravesite locations in serial killer cases matched many of the features and properties outlined by geocachers. The results also indicate the potential of using Keatley and colleagues’ Winthropping as a psychological profiling as well as geographical profiling technique. Support was provided through the case of a murdered child who was later dumped. Recommendations for further research and application are provided.

The Fate of Phosphorus in Experimental Burials: Chemical and Ultramicroscopic Characterization and Environmental Control of Its Persistency

The permanence of a buried body in soil always induces the formation of a decomposition island that can serve as a significant recording location to understand how the persistence of a clandestine grave affects soil. This study aims to analyze the elemental exchange from buried bodies to soil, with a focus on phosphorus content, and to determine the effects of environmental factors on its persistency. The experiment was carried out using eleven swine carcasses buried in an open site (northern Italy). The analyses were performed using the Olsen P method, which allowed for a recognition of the trend of the amount of phosphorus over time, due to the decomposition of phospholipids, followed by the transfer of the element from bone to soil. Additionally, microanalyses performed using a scanning electron microscope (SEM-EDS) on two different soil sample specimens (i.e., “dust” and “plug”) allowed for the identification of numerous phosphatic features (i.e., coatings, infillings, impregnations, and organo-mineral associations), which are the result of the interaction between soil and body fluids and can thus be used as indicators of the former presence of decomposing body (even in its absence). The ultramicroscopic analysis also shows increasing and decreasing amounts of P2O5 over time in the soil, which could be related to environmental conditions (i.e., soil moisture), due to the leaching of phosphorus induced by the percolation of natural rainwater. The study underlines the potential use of these methods to evaluate the possibility of a cadaver–soil linkage and of assessing the burial in the soil for a variable period. Moreover, the study may aid in analyzing the dynamics of phosphorus migration from buried bodies to soil during and after the decomposition process.

Devenir buscadora desde sitios de exterminio. El caso de las transmisiones digitales de las Madres Buscadoras de Sonora (2020-2021)

The article analyzes the geopolitics of becoming a digital searcher using the transmissions produced by the Madres Buscadoras de Sonora collective from the crematoriums and clandestine graves identified between December 23, 2020 and July 9, 2021 in the valley of Guaymas in the south of the state of Sonora, Mexico. The study is intended to highlight that the Madres’ search is immersed in a process of de-territorialized governmental necropolitical victimization, which drives them to go into the analyzed area. The work is based on the digital observation of the collective’s social network transmissions and on an interview with the leader during the protest that took place outside the Attorney General’s Office (FGR) on October 11, 2021, three months after the murder of Aranza Ramos Gurrola. The paper’s contribution lies in reconstructing the geography of the transmissions broadcast at the indicated place and time. It is argued that such transmissions are a way of sustaining low-resolution digital searching. For the Madres, becoming searchers is a task that involves maintaining a mobile digital infrastructure to translate the barbarism they encounter into a citizen forensis. The article shows that the Madres Buscadoras de Sonora’s pursuit of becoming digital searchers is immersed in a governmental necropolitics that does not produce citizens but victims.

An innovative procedure for cranial reconstruction as an aid for human identification

Human remains are frequently recovered fragmented from forensic contexts. Taphonomic factors and peri-mortem trauma can damage human remains recovered from clandestine graves. Therefore, an incomplete or broken skull can represent a challengeto identifying an individual, osteometric analysis, and trauma interpretation. A reconstructive approach is proposed to aid forensic experts in achieving all the information from human remains. This study proposes an innovative method that involves the use of reversible glue to connect the fragments. Non-permanent wax is used to reconstruct the missing parts and stabilize the skull. The reconstruction procedure is divided into three phases: cleaning, reassembling and remodelling. The reassembling is carried out with non-permanent reversible glue. Consequently, if the reconstructed remains do not have enough solidity to undergo a forensic examination, some of the missing anatomical parts can be replaced with reversible wax modelled on the missing bone’s shape. The method allows a more comprehensive examination of the whole skull structure for biological profiling of unknown individuals and a better analysis of trauma and injuries. Moreover, Computed Tomography (CT) and radiographic analysis can be better performed on areconstructed skull; the data obtained can also be a more appropriate background for unidentified persons’ facial approximations.

Mapping Decomposition: A Preliminary Study of Non-Destructive Detection of Simulated body Fluids in the Shallow Subsurface

The processes of decomposition that the body will have after the time of death are peculiar and complex. The body swells and expels gases and fluids, and the flesh decays. It also attracts many insects and scavengers. We know that these fluids are nutrients for the vegetation, and if the body is inhumed in the subsurface, they allow a rapid crop growth that remote sensors can mark. During forensic investigations, mapping the fluid migration in the subsurface can help reconstruct the genesis of a clandestine grave. Several studies show how different remote sensors and analyses can be sensitive to human burials. This paper presents a preliminary experiment studying the fluid dispersion in the subsurface using simulated body fluids in a shallow grave and detecting it through the ground penetrating radar (GPR) technique (given its ability to detect dielectric constant changes in the investigated media) and other remote sensing techniques. Although the simulation of the body fluids related to the dielectric constant was accurate and allowed us to better understand how decomposition in the subsurface does not always migrate in the way that was initially expected (toward gravity), other typical characteristics of the body fluids, other soils and external factors were left out and would be studied in future simulations.

Unraveling Crimes with Geology: As Geological and Geographical Evidence Related to Clandestine Graves May Assist the Judicial System

The geological and geographical evidence related to crime scenes involving clandestine graves is valuable data to consider during judicial investigations because it can provide useful criminological and criminalistic information. Research results on the nature and main features of historical cases and thirty criminal burials are reported. Among the studied cases, a recent homicide clandestine grave was analyzed through remote sensing. This latter allowed the definition of GIS-based RAG maps and search priority scenarios and ascertain that the study grave fell in a high priority Red coded area, validating a method previously based only on simulated crime scenes.

A Controlled Experiment to Test the Efficacy of Ground-Penetrating Radar in the Search for Clandestine Burials in Poland

The international workshop ‘Forensic Search and Recovery of Clandestine Graves’ took place over two days in 2021 in Wroclaw, Poland. The goal of the workshop was to improve search methods and techniques related to the examination of clandestine burial sites. Geophysical methods were used by an international team of multi-disciplinary specialists to detect simulated burial sites. The training focused on testing methods, including Ground-Penetrating Radar (GPR), to verify the effectiveness of the methods in the search for two features representing clandestine burials. The forensic community in Central European countries, including Poland, has been slow to adopt these technologies due to controversial results. While geophysical research is successfully carried out in archaeological research and forensic contexts internationally, its application in the activities of the prosecutor’s office and the police in Poland has been relatively unsuccessful. This has resulted in several controversies related primarily to the erroneous expectations of how the methods are successfully applied. This may be the result of operator inexperience in applying these methods to the search for clandestine burials. This training paired an experienced GPR operator with law enforcement teams and archaeologists, leading to the successful discovery of simulated burials using GPR.

Time-Lapse Electrical Resistivity Tomography Imaging of Buried Human Remains in Simulated Mass and Individual Graves

Electrical resistivity has been used as a noninvasive geophysical technique for locating clandestine graves and monitoring human decay within the subsurface. Detailed studies assessing resistivity anomalies due to soil disturbances and decay products associated with graves have relied on the use of proxies, such as pigs, with limited studies using real human cadavers and simulating a mass grave setting and none assessing the anomalies in 3D. In this study, we used time-lapse 2D and quasi-3D electrical resistivity distribution measured over an experimental mass grave and individual graves containing human cadavers to assess resistivity anomalies resulting from graves and the presence of decaying human remains in them. This study is part of a novel multidisciplinary mass grave experimental study with six graves consisting of a mass grave with six human cadavers, a controlled mass grave with none, three individual graves with one human cadaver each, and a control individual grave with none. Nine parallel resistivity transects which allow us to image these graves in their 3D context were acquired prior to excavation and 2 days, 1, 2, and 6 months after burial using a dipole–dipole electrode array, a unit electrode spacing of 0.5 m, and an interprofile spacing of 1m. The value of different electrode arrays and spacings in identifying the contrast between the graves was also assessed using forward models and field data. Soil sensors were installed at different locations in the graves to monitor soil electrical conductivity, moisture content, and temperature. The results of this study show an increase in electrical resistivity 2 days after burial in all graves with human remains and the control graves, which we attribute to increased soil aeration where disturbed pores are filled with air. The resistivity decreases thereafter in graves with human remains which we attribute to the formation of conductive leachates. This study validates the potential of electrical resistivity as a forensic search tool for locating both clandestine mass and individual graves and as a noninvasive monitoring technique to support human decomposition research.

Unidentified Bodies in the Mexican Context

The discovery of clandestine graves has become a recurrent event during the last ten years in Mexico, and there could be more than roughly 2000 distributed all over the country (Guillen et al. 2018). Mass graves specifically are less well-known, reported, and addressed; they are located in municipal or state cemeteries which house unidentified bodies and of which there is no official census. An estimated 26,000 bodies are considered unidentified (SEGOB 2019a), and every year in Mexico City alone almost 500 bodies are sent to the mass graves in cemeteries. Comprehensive efforts in forensic science are required to mitigate the high percentage of unidentified bodies and coordinate the correct burial and registration of bodies in mass graves. The ongoing humanitarian crisis and the complexity of the context require that investigators look at overlaps between cases of disappeared persons and unidentified bodies, and between searches and identification.

A multidisciplinary approach to locating clandestine gravesites in cold cases: Combining geographic profiling, LiDAR, and near surface geophysics

By nature, clandestine burials are difficult to locate, an issue that can complicate the legal process, and interrupt the natural grief process of the family. The purpose of this paper is to present a three-step process to search for clandestine graves using (1) geographic profiling, (2) light detection and ranging (LiDAR), and (3) near surface geophysics. Each process incrementally decreases the geographic area being searched, while increasing the level of detail provided to investigators. Using two well-known Australian cases and one experimental study, this paper will demonstrate how (1) can highlight potential search areas, (2) can further narrow down the location of potential burial sites within these search areas, and (3) can assist with locating the clandestine grave. Although each technique on its own can successfully locate graves, combining the techniques can provide the most efficient approach to locate those who are missing and buried.

Reconstructing the Memory of the Wounded Social Body: A Philosophical-Theological Reflection from the Search for Missing Persons in Mexico

This essay analyzes the phenomenon of clandestine graves of missing persons in Mexico as a social, political, and philosophical problem, where theological clues are established. With the contributions of decolonial thought this reflection seeks to think the absence and, within it, to think the emergence of an alternative world promoted by the just people of history with the resistances they create to live the present with dignity and hope.