Forensic anthropology

DEFINITION: Profession in which skeletal analysis is performed for the purpose of gathering evidence to be used in legal contexts, such as criminal investigations and civil disputes.

SIGNIFICANCE: Because bones are resistant to the process of decay, human skeletal remains can provide primary evidence of the human form after death. Characteristics of humans’ bones, and any marks preserved within, can reveal identity and causes of trauma. Such evidence is most frequently associated with homicide cases, but it can also be valuable in civil lawsuits, such as those involving the mishandling of remains. Forensic anthropologists are also sometimes employed to examine skeletal remains following mass disaster situations and cases of genocidal mass murder.

A subspecialty of physical anthropology, forensic anthropology came into being in 1878 when anatomist Thomas Dwight published an essay titled “Identification of the Human Skeleton: A Medico-legal Study.” The field reached its modern era in 1939 with the publication of Wilton Marion Krogman’s article “A Guide to the Identification of Human Skeletal Material,” intended as a basic primer for law-enforcement personnel about the use of anthropology in the American legal system. This work garnered attention for the field, and in 1962 Krogman expanded it into what many still consider to be the seminal text on skeletal identification, The Human Skeleton in Forensic Medicine. Forensic anthropology became an “established” area of study when the Physical Anthropology Section of the American Academy of Forensic Sciences (AAFS) was created in 1972. Five years later, the American Board of Forensic Anthropology was incorporated as a nonprofit certifying body to ensure the of persons practicing in the field.

Two additional important developments took place in the field of anthropology in the 1970s and the 1980s. First, the Anthropological Research Facility (ARF) was created in 1972 at the University of Tennessee, under the vision and direction of well-known professor and forensic anthropologist Dr. William M. Bass. Second, the Physical Anthropology Section of the AAFS began creating the Forensic Anthropology Data Bank (FDB) in 1986. Both events allowed researchers to gain significant insight into modern skeletal variation and analysis. The ARF, more commonly known as the "Body Farm," is an outdoor laboratory where human corpses are left to decompose under various conditions, thus allowing for the study of decay, skeletal remains, and insect evidence; four other body farms were subsequently established at universities in North Carolina, Texas, and Pennsylvania, and in 2015, Australia's University of Technology, Sydney, began construction on the first human body farm located outside the United States. By the 2020s, eight body farms had been established in the US. The FDB contains extensive demographic and skeletal information for more than two thousand sets of remains, both identified and unidentified.

Uses of Forensic Anthropology

The most common use of anthropological evidence is in the determination of the identities of deceased persons. Forensic anthropologists gather as much skeletal information as possible to create profiles of distinguishing traits. For example, an intact femur (thighbone) can be measured and mathematically analyzed to reveal height because the length of the femur has a linear relationship to human stature. This information can then be used to determine whether the remains in question are those of a specific human being, such as a particular missing person. Alternatively, the traits identified by forensic anthropologists can be incorporated into descriptions that can serve as the bases for facial reconstructions and drawings.

Anthropologists also use identifying characteristics to separate and identify individual victims of mass fatalities where remains are mixed. This often occurs in the context of natural disasters (such as the aftermath of Hurricane Katrina in 2005), airplane or train wrecks (such as the 1996 crash of Trans World Airlines Flight 800), terrorist attacks (including the World Trade Center attacks in 2001), and mass graves (as created during the genocide that accompanied Rwanda’s 1994 civil war).

Anthropologists can also uncover details about the circumstances surrounding homicides. Signs of skeletal trauma can reveal what types of instruments or methods were used to cause fatal injuries. Knife marks preserved in bone, for example, imply that the victim was stabbed; a cracked hyoid bone suggests strangulation. In some cases, skeletal evidence may also reveal whether injuries were self-inflicted, accidental, or the result of criminal activity. For instance, evidence of repeated blows to the back of the head would seem to be indicative of assault rather than suicide.

Anthropological analysis may also shed light on the timing, or sequence, of trauma to a body. This is frequently seen in the case of gunshot wounds to the skull, wherein intersecting fissures allow the analyst to determine the order of bullet entry. Forensic anthropologists may also use bone evidence to estimate how much time has passed between a person’s death and the discovery of the remains.

In a few rare instances, forensic anthropologists have been called upon to identify persons who are still living—specifically, criminal perpetrators. In these situations, practitioners are asked to compare the anatomical features of suspects, such as their hands or feet, with evidence. This evidence can take many forms, including handprints, footprints, photographs, and surveillance videos.

The Process of Identification

The first step in any skeletal analysis is the recovery of the remains, which may have been discovered by accident or in the course of an investigation. Ideally, anthropologists examine the evidence at the site of discovery (in situ) and collect the skeletal material themselves. This is the preferred method because after the remains are disturbed, it is impossible to recreate the original relationship between the environment and the remains with complete accuracy. Many forensic anthropologists, however, work in an academic rather than governmental environments, and thus skeletal matter is frequently collected by evidence technicians. These technicians are trained to search for, photograph, recover, and label physical evidence. They may also map out key scene features, such as natural landmarks and bone location, sometimes using a grid pattern for reference. Recovery must be methodical and meticulous, as the very process itself is destructive to evidence. The ability to identify clandestine graves is often critical at this stage.

After anthropologists receive remains for examination, they must first determine whether the material in question is actually bone. This can usually be done with the naked eye, but the use of a microscope or chemical analysis may be necessary if the remains suffered severe damage such as burning or fragmentation. When the material has been positively identified as bone, the practitioners must determine whether the skeletal matter is from a human or a nonhuman. Again, this can normally be determined through visual inspection, especially if the anthropologists compare the questioned material against known animal specimens. If the remains are very small pieces or in very poor condition, however, examination of the microscopic structure of the bone may be required.

Next, the examiners must determine whether the bone is of such an age as to be of forensic significance. Generally speaking, skeletal remains are of archaeological rather than forensic interest if they are from a person who has been dead at least fifty years. All available environmental factors, such as weather and burial conditions, are considered in this assessment, which is also known as the determination of the postmortem interval. Making such estimations is not an exact science, so anthropologists usually express their opinions on postmortem intervals in the form of ranges or approximations.

After these preliminary questions are answered in the affirmative, the process of personal identification can begin. First, the skeletal material is classified according to such general features as sex, ancestry, stature, and age at death. Practitioners distinguish these features by analyzing traits—particularly measurements—that correlate with particular subgroups of humans, such as female humans or adult humans. Although the discernment of some of these traits requires microscopic comparison, many traits are outwardly recognizable. For instance, most forensic anthropologists can determine the sex of adult remains simply by viewing the pelvic structure, which is designed to accommodate birth in female but not in male humans.

All members of a subgroup do not exhibit identical features, however, so anthropologists must consider ranges of variation within each subgroup. The ranges they use are based on data gathered from collections of documented skeletons, such as the Robert J. Terry Anatomical Skeletal Collection at the National Museum of Natural History in Washington, DC; the Hamann-Todd Human Osteological Collection at the Cleveland Museum of Natural History; and the FDB. Anthropologists also use a specialized software package called FORDISC to interpret their measurements. Developed by researchers at the University of Tennessee, this interactive computer program allows practitioners to classify adults by sex or ancestry through any combination of standard dimensions.

The general characteristics determined through the examination are then assembled into a description that may in turn lead to a tentative identification. For example, the profile of a missing thirty-eight-year-old White man, approximately six feet two inches in height, may correspond with found skeletal material. A specific, positive identification is not possible, however, until features that are unique to an individual—not just a subgroup—are matched to the remains. Practitioners start this process by gathering as much data as possible about the tentatively identified person. Often medical records will reveal key distinguishing features, such as healed fractures, bone disease, or surgical implants. Additionally, if facial portions of the skull are found, a reconstruction can be generated and compared with photographs of the person during life.

In addition to identifying the deceased, anthropologists can provide information about bone trauma, particularly as it relates to cause of death. Skeletal injury generally falls into one of three categories: gunshot wounds, blunt trauma, or sharp trauma. Practitioners use visual observation and three-dimensional digital reconstructions to detect and analyze evidence of skeletal injury.

In the case of gunshot wounds, anthropologists generally try to determine the direction of fire (the projectile’s assumed path of travel), whether the marks on the bones are entrance or exit wounds, the caliber of the bullet, and, if multiple bullet marks are found, the sequence of shots fired. Fissure patterns and the appearance of individual wounds, especially whether the edges are beveled, are critical features in this analysis. In cases where persons have died from blunt force trauma, anthropologists examine the resulting unhealed fractures. In some instances, these fractures may be depressed in shapes identical to those of the instruments used to inflict the injuries, allowing for identification of the weapons. In situations involving sharp force trauma, most commonly stabbings, knife marks are usually found in the rib cage or on adjacent bones. Cut marks may also be found at the ends of arm or leg bones, suggesting that the perpetrator dismembered or de-fleshed the body in an attempt to prevent discovery or identification.

Forensic anthropologists are often asked to determine whether skeletal injuries were inflicted before death (antemortem), at the time of the death (perimortem), or after death (postmortem). Practitioners can readily identify whether certain artifacts, such as concretions or cracks, resulted from postmortem events such as chemical erosion, animal activity, or intentional displacement. The key feature in this analysis, however, is the trademark sign of antemortem trauma: evidence that the injury has healed. Antemortem trauma, although not always indicative of the cause of death, is still important in criminal investigations because it may suggest that the victim was tortured or otherwise abused prior to death.

The accuracy of skeletal analysis, whether it is used to determine identity or cause of trauma, depends on the quantity and quality of skeletal remnants available for examination. Anthropologists frequently work alongside other forensic specialists who can confirm or support their conclusions, including odontologists and pathologists.

Bibliography

Bass, Bill, and Jon Jefferson. Death’s Acre: Inside the Legendary Forensic Lab—the Body Farm—Where the Dead Do Tell Tales. Putnam’s, 2003.

Byers, Steven N. Introduction to Forensic Anthropology. 5th ed., Routledge, 2017.

Diaz, Olivia. "A Va. Research Farm Prepares to Receive a Key Addition—A Dead Body." The Washington Post, 7 Aug. 2023, www.washingtonpost.com/dc-md-va/2023/08/07/george-mason-university-body-farm/. Accessed 18 Dec. 2024.

Krogman, Wilton Marion, et al. The Human Skeleton in Forensic Medicine. 3rd ed., Thomas, 2013.

Reichs, Kathleen J., editor. Forensic Osteology: Advances in the Identification of Human Remains. 2nd ed., Thomas, 1998.

Safi, Michael. "What Lies Beneath: Sydney Gets the Southern Hemisphere's First 'Body Farm.'" The Guardian, 30 Jan. 2015, www.theguardian.com/australia-news/2015/jan/31/what-lies-beneath-sydney-gets-the-southern-hemispheres-first-body-farm. Accessed 12 Mar. 2015.

Steadman, Dawnie Wolfe. Hard Evidence: Case Studies in Forensic Anthropology. 2nd ed., Prentice, 2009.

Ubelaker, Douglas, and Henry Scammell. Bones: A Forensic Detective’s Casebook. 1992. Evans, 2000.

White, Tim D., and Pieter A. Folkens. The Human Bone Manual. Elsevier, 2005.