Taphonomy was developed within the disciplines of paleontology, archaeology, and paleoanthropology (Haglund & Sorg, 1997). Forensic taphonomy focuses on reconstructing events at and following death. This is done through collection and analysis of data, distinguishing perimortem and postmortem alteration of remains, estimating how long the remains have been at the site, and estimating time of death.

Human remains may be encountered in mountains, glaciers, deserts, rain forests, and farm fields, and it is imperative to answer questions about what happened to the body before death, at the time of death, and after the remains ultimately reached a final resting place. Each of these sites is likely to produce important information regarding the length of time since death and how body decomposition and dispersal has been affected by the unique environmental characteristics of each locale. The taphonomist, working with other forensic investigators, is better able to answer these questions after having studied similar scenarios where known characteristics can be matched. However, some of these case findings are so unique that little or no prior information is known about the normal processes of decomposition and disarticulation in that given location.

The increasing importance of such knowledge was the stimulus for the origination of NecroSearch International, Inc., a nonprofit, volunteer organization dedicated to research, education, and investigation in the location of clandestine graves, the recovery of the remains, and the investigation of associated evidence in and around the graves (France, Griffin, Swanburg, et al., 1997). Volunteers consist of individuals from law enforcement, investigations, serology and chemistry, forensic nursing, forensic anthropology, archaeology, entomology, geology, pedology, geophysics, geochemistry, petrology, photography and aerial photography, thermal imagery, meteorology, botany, wildlife biology, and criminal psychology. Naturalists and computer data analysts are the other valuable personnel associated with the project. Scent-detecting dogs and their handlers, as well as other outside resources, may be obtained as needed in certain phases of the project studies.

The concept of utilizing scientific techniques in locating clandestine graves originated in 1987 by a group of law enforcement investigators and scientists who were frustrated by conventional grave location methods such as large-scale ground searches and trial-and-error excavations employing heavy equipment (France et al., 1992, Haglund et al., 1990 and Imaizumi, 1974). In 1986, law enforcement originated a search on a 2200-acre ranch located approximately 30 miles west of the Kansas border near Stratton, Colorado. According to information provided by an informant, up to a dozen bodies had been buried in an area of several square kilometers over the course of several years. Three bodies were unearthed and recovered through the use of backhoes, which unfortunately destroyed not only the crime scene but also much of the evidence. The remaining area was then arbitrarily trenched and plowed as investigators searched for further remains but turned up none. Because of the destructive and intrusive methods used in the search, further detection utilizing scientific methods proved ineffective. It was then and is still believed that additional bodies remain undiscovered on the property.

Because of the limitations found with traditional methods in the location and excavation of clandestine graves, the basis of the NecroSearch research began with Project PIG (“Pigs in Ground”). In 1988, a study of the relationships between buried pig carcasses and their surroundings was implemented using various techniques from the scientific community and applying the results to actual cases of buried human remains. The multidisciplinary project involved law enforcement agencies, scientists, private businesses, and academicians (France, et al., 1992). The information gained in this research had traditionally been obtained separately if at all. It should be noted that there is no singular technology that can determine if a body is buried beneath the surface; however, a compilation of all the techniques can identify a particular site or number of sites that are the most likely to be the location of a clandestine grave. In the same vein, compiling these techniques may also determine that there are no disturbances beneath the surface in a given area, saving time and unnecessary excavations (Hoving, 1986 and Killam, 1989). Success is not always measured in recovery of remains, but sometimes in knowing where not to dig.

Pigs were originally used for burial at the research site, and they continue to be used for the following reasons. First, Colorado law does not allow human cadavers to be used for these types of studies. Second, pigs have a fat-to-muscle ratio similar to humans, and their skin is not heavily haired. The pigs used in this research were similar to humans in weight (70 kg/154 pounds), although some smaller pigs were included to simulate bodies of different ages or sizes. Third, pigs have been previously used in studies of patterns and rates of decay and scavenging because they have been considered to be similar to humans biochemically as well as physiologically.

The site of the original NecroSearch project was approximately 20 miles south of Denver, Colorado, on the Highlands Ranch Law Enforcement Training Facility property (Fig. 22-1). The site was selected because it offered proximity to human and physical resources and yet had strict operating procedures and security barriers to control public access. Baseline data, including a series of black-and-white aerial photographs, geophysical measurements, and environmental observations of the site, were carefully recorded before the burial of the first pig. Aerial photography is the least destructive method, because it is virtually nonintrusive. It provides an excellent characterization of a particular site, including the access, culture, drainage, and topography. In addition, an extremely large area can be covered in a relatively short time. Preburial photographs may be available from a variety of sources including the U.S. Geological Survey (USGS), county planning boards, utility companies, and railroads.

Near-field factors (i.e., interacting with the burial system) and far-field factors (i.e., uninfluenced by the burial system) were recorded before and after the burial of each pig carcass to appreciate physical site disturbances associated with the burial processes (Fig. 22-2). Other research components included calibration pits (graves without an interred pig) and a control site (undisturbed at both the surface and the subsurface). The latter site is necessarily remote from where pigs have been interred. The back dirt (i.e., excess soil deposited near the perimeter of the grave or calibration pit) serves as a valuable marker of gravesites, useful even with aerial photography used to identify near-field characteristics. Vegetation growth patterns, soil markings associated with excavational boundaries, and snow settled in grave depressions were phenomena visible from the air. Because an extended period must elapse before the gravesite returns to its original state, pig burial sites continue to be monitored and photographed on a regular basis. Climatic conditions, seasonal changes, and freezing/thawing cycles affect soil properties and change the land’s appearance when viewed from the air (Fig. 22-3). The best aerial photographs result from using a large film format, which allow investigators to fully appreciate the details of vegetative or terrain changes.

Researchers prepared a list of all plants within the law enforcement training site including all plants growing on graves, calibration pits, and back dirt areas. When a grave has been created and a body buried, certain vegetation is destroyed and secondary successions are set into motion (Bass & Birkby, 1978). Five years after the pig burials, it was noted that undisturbed plots contained the greatest diversity in plant species, both weeds and wild flowers. After burials, the plots showed little species diversity. Although eventually other species invaded from the surrounding undisturbed areas, plots did not recover the plant mixture that they originally possessed. It should be noted, however, that even in graves that no longer contained pigs because of intentional disinterment or animal scavenging, revegetation characteristics were identical to those that still contained a pig. Warmth associated with a decaying pig in the ground and the presence of certain nutrients added to the soil did not seem to support or inhibit plant growth. It is evident from the NecroSearch findings that knowledge of native plants in an area can provide valuable clues to the site of a clandestine grave, particularly where the vegetation is largely otherwise undisturbed.

Burial of a corpse hinders the normal faunal succession of arthropods, many of which are useful as forensic indicators (Smith, 1983). Control sites with traps were created to study airborne and surface insects at 1, 2, 4, 7, 12, 25, and 30 days post-pig burial. There were no readily visible entomological indicators of the buried pigs, such as surface stains from saponification or liquefaction 30 days after the burial. The blowfly ( Calliphora vomitoria) was noted in the Malaise trap within 24 hours of burial, and Phormia regina arrived 48 hours postburial. In two weeks, significant numbers of blowflies were trapped at the active graves compared to control sites. Pit traps did not capture any arthropods, typically considered to be forensic indicators (Payne, King, & Beinhart, 1968).

When searching for clandestine graves, the team must consider many factors when choosing tools and other resources to aid in their work. The place, weather, and season are just a few of the factors that must be carefully considered. Methods used to detect clandestine graves include aerial photography, geology, botany, entomology, geophysics and magnetics, electromagnetics, ground penetrating radar, self-potential, soil gas, metal detection, thermal imagery, decomposition dogs, naturalists, archaeologists, and forensic physical anthropologists. The methods selected to aid in the search efforts maximize the team’s efforts and minimize any impact on the environment.

Many methods are considered advantageous because they are nonintrusive; however, often these methods can also be limiting. For example, ground-penetrating radar is nonintrusive, yet it is limited because the equipment is difficult to obtain. In the same way, a metal detector is relatively nondestructive and nonintrusive and can easily detect bullets, jewelry, and other metallic objects (Fig. 22-4). However, this method assumes there is metal on the body.