Taphonomy (Forensic Science)
The term “taphonomy” was coined in 1940 by the Russian paleontologist Ivan Yefremov to describe the “laws of burial.” Taphonomists attempt to understand events that occur to organisms after death, a period defined as the postmortem interval. Early research in the field of taphonomy focused on the study of fossils, especially the conditions that determine how and why certain organisms are preserved in the fossil record. Since the 1980’s, taphonomy has become an important research area in forensic science, focusing on the study of postmortem changes in human remains and estimation of the time since death (TSD), also known as the postmortem interval. This emerging field, known as forensic taphonomy, applies the principles of taphonomy to the study of human decomposition. TSD studies are usually undertaken by anthropologists, entomologists, or pathologists who have forensic expertise, but the examination of postmortem changes in human remains is an interdisciplinary study and may involve a number of different specialists.
(The entire section is 155 words.)
Goals of Forensic Taphonomy (Forensic Science)
Forensic taphonomy addresses several important medicolegal issues, including estimation of the TSD and the study of postmortem changes in human remains caused by decomposition, transport, weathering, or fire. TSD estimation can aid in narrowing down the search for a missing person or can be used to exclude potential suspects from consideration who have alibis for the time when an alleged homicide occurred.
When a corpse is exposed to the environment for a long period of time, estimation of the TSD becomes increasingly difficult. Over time, insects, bacteria, plants, animal scavengers, and other aspects of the physical environment alter remains. Postmortem changes to remains can potentially be misinterpreted as perimortem wounds—that is, trauma inflicted at or around the time of death.
Different taphonomic processes also leave distinct signatures, so the ability to differentiate postmortem changes from perimortem trauma is critical. For example, tooth marks on bone from animal scavenging should not be misinterpreted as perimortem trauma. Taphonomic studies require close examination of the condition of the remains and any alterations caused by the environment. Humans are also considered taphonomic agents, as a perpetrator may be involved in transporting or altering (for example, mutilating or dismembering) remains after death.
(The entire section is 198 words.)
Stages of Decomposition (Forensic Science)
When human remains are discovered, one of the first questions asked is, How long has the victim been dead? Decomposition typically occurs in the following predictable sequence of stages: the fresh stage, the bloat stage, the active decay stage, the advanced decay stage, and the dry or skeletal stage. The rate of decay, however, is influenced by a number of factors in the immediate environment, such as temperature, humidity, moisture, availability of insects and animal scavengers, and soil conditions. Bodies that are found indoors or that are buried decompose at slower rates than remains that are deposited on the surface of the ground. In the case of a recent death, medicolegal investigators examine the body for early signs of decomposition.
Changes during the fresh stage of decomposition generally occur within the first few days postmortem. Immediately after death, the body cools until it reaches ambient temperature, a process known as algor mortis. Pooling of blood into the capillaries of the skin, or livor mortis, follows and is fixed by approximately twelve hours after death. Rigor mortis, the hardening of the muscles, begins about two hours after death but may last for up to twenty-four hours.
The bloat stage is marked by the buildup of gases within the body, which causes the abdomen to be distended. The skin also becomes discolored and marbled in appearance. This process may last for several days up to a...
(The entire section is 350 words.)
Taphonomic Studies (Forensic Science)
Although some taphonomic studies occur within laboratory settings, most research is conducted outdoors with the remains of nonhuman animals, such as pigs. In some locations, however, donated human cadavers are used to study decomposition rates; the Anthropological Research Facility at the University of Tennessee, Knoxville, popularly known as the Body Farm, is perhaps the most widely known example of this kind of research center.
With the establishment of increasing numbers of outdoor taphonomic research facilities in different locations, scientists have been able to gain reliable data on variations in decay rates. These studies, which contribute to an in-depth understanding of the process of human decomposition, provide law-enforcement investigators with information they need to make more accurate estimates of time since death.
(The entire section is 121 words.)
Further Reading (Forensic Science)
Galloway, Alison, et al. “Decay Rates of Human Remains in an Arid Environment: Retrospective Study of Decay Rates in the Southwestern United States.” Journal of Forensic Sciences 34 (May, 1989): 607-616. Reports on the findings of a scientific study of decay rates.
Haglund, William D., and Marcella H. Sorg, eds. Advances in Forensic Taphonomy: Method, Theory, and Archaeological Perspectives. Boca Raton, Fla.: CRC Press, 2002. Detailed edited volume focuses on theoretical and practical applications of taphonomy in medicolegal settings.
_______. Forensic Taphonomy: The Postmortem Fate of Human Remains. Boca Raton, Fla.: CRC Press, 1997. Collection of essays highlights case studies and research dealing with taphonomy in medicolegal settings.
Komar, Debra A. “Decay Rates in a Cold Climate Region: A Review of Cases Involving Advanced Decomposition from the Medical Examiner’s Office in Edmonton, Alberta.” Journal of Forensic Sciences 43 (January, 1998): 57-61. Reports on the findings of a study of variability in decay rates of remains found in cold climates.
Lyman, R. Lee. Vertebrate Taphonomy. New York: Cambridge University Press, 1994. Provides a comprehensive overview of the science of taphonomy for archaeologists, physical anthropologists, and paleontologists.
(The entire section is 178 words.)
Taphonomy (World of Forensic Science)
Taphonomy, from the Greek, taphos, meaning tomb or grave, and nomy, meaning classification, is a field of paleontology, paleo-anthropology, and bioarcheology that studies human and animal remains in relation to the post-mortem (after death) transformations that occur in burial sites. In a broader sense, taphonomy is the study of the processes that leads to fossilization, as well as the stages of transformation of remains through the action of environmental factors. The knowledge gathered by this field is important to forensic science as a tool for the analysis of human remains at old crime scenes, mass graves, and mass disaster areas.
Osteology (or the study of bones), geochemistry, and entomology (the study of insects) are important aspects of taphonomy, as skeletons and skeletal fragments may yield information on the living conditions, availability of food, presence of infections, wear and tear of specific joints due to repetitive effort, size of muscles, and post-mortem events. Therefore, a scenario of living organism versus environmental characteristics may be inferred from such analysis as well as which forces and agents have acted over the remains after death. When the organism dies and is buried or covered by sedimentary layers of soil, such as clay, sand, volcanic ash, or ice, the taphonomic process of post-mortem transformations begins, which can lead to different types of mummification, decomposition, or skeletonization. If the conditions are right, skeletal fossilization will eventually occur. Bones can also be modified by animal scavenging, or be carried by rivers and scattered on riverbanks far from the original site of death before fossilization occurs.
Taphonomy studies three different stages of post-mortem transformation: necrology, biostratinomy, and diagenesis. Necrology refers to the factors present around the time of death or directly associated with the cause of death. Necrologic studies could include examination of bones or bodies for skull fractures, marks of fangs or claws in bones, signs of malnutrition, abscesses, infections, lesions by blunt instruments, bullets, or incineration, among other clues to the cause and events surrounding death. Biostratinomy identifies the changes that occurred after death such as decomposition and changes due to environmental forces acting in burial sites (tombs, graveyards, mass graves), or in places where remains were left or found, such as river or lake bottoms, sedimentary soils, or woods. Several events from this stage may leave their marks on the remains, such as animal scavenging, enzymatic and bacterial activity, insect activity, and transportation by water or landslides. Eventually, some bone fragments or entire skeletons may be buried under conditions that favor diagenesis, the process of lithification (compaction) of the sediments that envelop the remains, ultimately resulting in fossilized bones. Fossilization may occur in terrestrial (earth) and maritime (water) environments, and give clues to researchers about the environmental, geological, topographical, and climatic changes that occurred on Earth throughout the process of fossilization. The study of submarine layers of fossilized marine animals and crustaceans, for instance, allows the description of radical climate changes that occurred in different geological eras.
Forensic taphonomy focuses on the perimortem (at the time of death) and intermediate postmortem (days to weeks after death) biological and biochemical transformations in order to determine the cause of death, estimate the approximate time of death, and to identify humans remains including the sex, age, race, and, whenever possible, the individual's identity. The understanding of how different environments interfere with the biological and biochemical changes in human remains, affecting the process of decomposition, is crucial for the forensic interpretation of mass graves, mass disasters, war crimes, and cold cases of murder.
SEE ALSO Animal evidence; Anthropology; Body Farm; Death, cause of; Decomposition; Entomology; Exhumation; Geology; Medical examiner; Mummies; Osteology and skeletal radiology; Pathology; Skeletal analysis; War forensics.