Diane L. France, Ph.D., D.A.B.F.A.
Director, Laboratory for Human Identification
Colorado State University
Contents
WHAT DO FORENSIC ANTHROPOLOGISTS DO?
DETERMINATION OF ANCESTRY/RACE
FACIAL RECONSTRUCTION/APPROXIMATION
- Mechanical Forces
- Blunt Force Trauma
- Cut Marks
- Gunshot Wounds
- Healing of Bone
- Disease Process
- Resolution of the Case
This module will introduce you to the essentials of forensic anthropology, especially as practiced in the United States and Canada. Forensic physical anthropologists take the basic understanding of the human body, as provided by physical/biological anthropology, and add to it the principles of medico-legal investigations of identity and the circumstances of death.
Forensic physical anthropologists specialize in the research and application of techniques used to determine age at death, sex, population affinity, stature, abnormalities and/or pathology, and idiosyncrasies to (usually) modern skeletal material. Forensic science is defined as the application of scientific methods to the law. Forensic physical anthropology is the application of various techniques of physical anthropology to legal questions. The term "forensic anthropology,” in a strict sense, can be used to describe any situation in which the techniques of any aspect of anthropology are applied to the law. Archaeology, primatology, paleoanthropology, etc., can be called forensic anthropology if they are applied in this way. However, in this module (as in common professional usage), forensic anthropology will refer to the use of physical/skeletal biological methods only. In keeping with the holistic nature of anthropology, forensic anthropology incorporates information and techniques from fields such as anatomy, physics, chemistry, pathology, law enforcement, and others. As in many other fields in science, the advancement of forensic anthropology developed as a need to find improved methods in order to identify remains in law enforcement or in war.
The techniques used in forensic physical anthropology are often used in describing non-forensic cases — such as archaeologically-derived specimens — but that use, strictly speaking, is not forensic anthropology. In fact, it is this difference in application and context that distinguishes forensic anthropology from the other subdisciplines of physical anthropology. Moreover, forensic anthropologists know they must be prepared to defend any professional statements they make in court.
The first contact a forensic anthropologist receives usually comes from law enforcement officials. Moreover, forensic anthropologists do not strictly work for the prosecution, and, likewise, they are not solely involved in criminal cases. Forensic anthropologists frequently work with the defense in criminal cases, and they assist in civil cases as well. Strictly speaking, forensic anthropologists should be willing to answer questions as they arise, regardless of from which side they originate. If, in a criminal case, the expert witness — such as a forensic anthropologist — was to choose not to fully answer questions for either the prosecution or the defense, he or she has already determined the guilt or innocence of the defendant. In our judicial system, that right belongs to the jury or judge, not to the person who has been asked to render an expert opinion about certain facts in that case. Forensic anthropologists work for the victim, and, as long as they tell the truth, justice will be served.
Forensic anthropologists often work with coroners and medical examiners in the identification of individual skeletons in which the identity of the remains cannot be established by other means (dental identification, fingerprints, or DNA, for instance). Those remains do not have to be skeletonized in order for skeletal clues to be useful, and frequently forensic anthropologists are called to assist with decomposed, burned, or fragmentary remains. As referenced in Box 1, forensic anthropologists are also called to assist in the recovery and identification of remains from mass fatality incidents, including plane crashes, building explosions, and other circumstances in which the remains are fragmentary and commingled (remains from one individual mixed with those of other individuals). The information from the skeleton can even be used to help establish whether two photographs likely represent the same individual.
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Mass Fatality Incidents: The World Trade Center Increasingly, forensic anthropologists are responding to mass fatality incidents to help other experts in the identification of the deceased and to help recover materials and evidence from the scene of the incident. We have responded to, among other disasters, airplane crashes, building explosions, cemetery floods, and the more recent terrorist attacks on New York City, Washington DC, and Pennsylvania. In the early 1990s, a team of forensic specialists called DMORT (Disaster Mortuary Operational Response Team) was formed. This team is supported by the United States government under the U.S. Public Health System. It consists of forensic pathologists, forensic odontologists (dental experts), forensic anthropologists, radiologists, fingerprint experts, security officers, funeral directors, computer specialists, photographers, and others, all working to establish the identity of the victims and to investigate the circumstances surrounding their deaths. Team members are on standby 24 hours a day, seven days a week, prepared to respond to federally declared mass fatality incidents on U.S. territory. We do not respond to all disasters but only to those which involve more deceased individuals than can be processed by the local experts. At that point, the team members who are called to assist become temporary federal employees for the duration of their response. I am a long-term member of DMORT and have responded to many mass fatality incidents, including plane crashes and building explosions. Although I have worked on many human identification cases since I received my Ph.D. in 1983, nothing compares to a mass fatality incident. We are required to work twelve to thirteen hours a day, seven days a week for two weeks. At that point, we are strongly encouraged to leave the scene for at least a short time so that we don't burn out. The work is intense. The emotions are intense. Many people ask what goes through my mind when I receive the call to respond, and the short answer really is “everything.” Sometimes you must arrive at your closest airport within hours, so some of what goes through a person's mind is of a practical nature. I have to prepare my home, my dog, my small business, and pack within those few hours. At the same time, though, my mind is becoming focused on the mission. What will be required in setting up the temporary morgue? What will we have to do at the scene to recover the remains? When the plane is leaving the runway, I always wonder how I will be a changed person when I return. When we arrive at the scene, the adrenalin level and the focus level are both high. Frankly, I think that this is part of the appeal for responders, as well as for firefighters and law enforcement officers, who are in the middle of intense situations. Unquestionably, it is horrible to see this level of human tragedy, and we certainly see things that no person should ever have to see. But, an experienced responder will look beyond those things to search for clues which will identify the deceased. That is what I mean by focus. During the time we are at the scene, almost nothing else in the world exists (even to the point of having to be reminded to drink plenty of water, eat, and to rest). Also, it has long been recognized that people who share a common intense experience often form a close bond that lasts forever. Many of the people with whom I have responded to mass fatality incidents are now like family to me. When I hear of a plane crash or some other mass fatality incident, I usually start to pack, thinking that I may be called to assist. On September 11, 2001, I initially could only stare at the television, stunned as the rest of the world was, when the second plane hit the World Trade Center. After about a half hour, I started to pack, but, because the airports were immediately closed, I was not able to respond to the disaster until late September. For the duration of my stay, I was asked to work at the landfill on Staten Island. The situation was incredible. In fact, this is a term that is used repeatedly by everyone describing the events and the response: “incredible.” The environment at the landfill was dirty, noisy, and dangerous. Materials were brought from “Ground Zero” to the landfill on barges and were stacked at the landfill waiting to be processed. The large pieces of metal (primarily beams) were stacked at one end of the landfill to await transportation to the recycling centers. Everything else was sorted by large machines and by hand. At first, the materials were taken from the stacks — which were up to about 35 feet tall — by cranes to giant shakers and conveyor belts. These machines sorted the materials into different sizes. The larger materials were taken from this process to the recycling areas or to permanent disposal, but the medium and smaller materials were sorted by workers with rakes or literally by hand. We were looking for only two things: human remains and airplane parts, especially the “black boxes.” We wore hazmat suits, complete with heavy boots, masks, goggles, hardhats, gloves, earplugs, and tyvek coveralls. This protected us from most of the environmental hazards — not the sharp objects, of course — but it didn’t isolate us from the heat, cold, and noise. It was like a Jurassic ballet with all of the cranes working at once. When one crane dipped its head, another lifted its cargo. The ground shook every moment from the vehicles with tracks moving across the landscape. Methane bubbled from the ground from the previous landfill debris. The work continued around the clock. And believe me, it was hard work. The lines of individuals who were sorting this debris by rakes and by hand were primarily from various law enforcement and investigative agencies. When I wasn’t in the crime scene trailer sorting human from nonhuman remains (nonhuman because there were many restaurants in the WTC area), I was among those sorting on the lines. I regularly work out in a gym and am in pretty good physical shape, but I was soon exhausted. All of the sorted organic materials were sent to the New York Medical Examiner’s office, where materials were logged and identification techniques were initiated. But the truth is that no one works independently at a mass fatality incident, and that is even more true in a situation as horrific and massive as those events that occurred on September 11. Many responders have written of their personal experiences on that day — from the mountain climbers who descended into the jagged depths of the debris to the chefs from across the country who volunteered to cook for the workers. I worked with the New York Police Department detectives who were reassigned from their regular shifts or who, in some cases, worked their regular shifts and then reported for extra duty. Most of these detectives had watched as the Twin Towers were built, and now they had to sift through the debris. I would work with them again in a heartbeat. Everyone from DMORT was able to go home to a regular routine after staying for two weeks or a little longer. These folks had to stay for the duration and will still be there years from now. All of us responded in different ways to the national tragedy. However, for the local emergency responders, this tragedy happened in their home. |
How do forensic anthropologists work with other experts in the investigation of the kinds of cases described above? Involvement varies, depending on the nature of the case, but often the first step is to help in the location and recovery of bodies from surface deposits or from “clandestine” (secret and, usually, with criminal intent) graves. This, by the way, is a relatively new aspect of forensic anthropological work, in that previously most forensic anthropologists only performed laboratory analysis. It makes sense, however, that the context in which a body is discovered can be important to the evaluation of the remains, including marks on the bones, the amount of time that has elapsed since death, etc. For example, if a body with blunt force trauma to the legs is brought to the laboratory, the diagnosis of the mode of trauma might be different if the body was discovered near a highway, under a cliff, or in the middle of a flat field. In another situation, the analysis of a crime and the presentation of evidence in court might be different if the victim’s left arm was missing because the grave was disturbed by scavengers as contrasted to a grave undisturbed at the time of discovery.
In the search for a clandestine grave, forensic anthropologists should be part of a team of experts who look for changes in the surrounding environment that tell them the area has been disturbed. This team is always under the direction of the law enforcement agency in charge of the case, so that the inquiry is not compromised by well-meaning, but uninformed, volunteers arriving at a scene to help.
Naturally, a disturbance in the environment does not necessarily mean that a grave has been discovered. So, what are some of the clues to look for in finding a clandestine grave? When someone digs a hole, the site is changed in predictable ways, depending on environmental circumstances. For instance, the changes to a grave over time in very wet environments will be different than those in very dry environments. In any environment, plants within the hole are destroyed as the root system is compromised. Plants under the dirt thrown from the hole will be damaged, but they will usually recover relatively quickly from the insult. If the ground had previously been completely undisturbed, the layers of dirt are predictable, in that the more organic layers (those formed by the decomposition of plant materials) are close to the surface, while the rockier layers are deeper. When the dirt is removed, those layers are mixed, so that when the dirt is placed back into the hole, the layers no longer exist. In addition, often the lighter layers (less organically rich) will show on the surface. The ground is often mounded if the perpetrator wants to return all of the dirt back to the hole, and it will become quickly depressed after precipitation compacts the soil within the grave, particularly if the perpetrator left the surface flat. So, for starters, one would look for damaged plants or bare ground and either mounded or depressed ground with the layers mixed — which is determined when a small test trench is dug into the suspected grave.
If a significant period of time elapses between the time of burial and the time of the search, plants will begin to colonize the disturbed area. Again, environmental circumstances have an influence here. For instance, the plants in a wet environment may colonize the grave within a season while a grave in an arid environment may remain relatively bare for years. Even smaller environmental differences, such as the seasons of the year or whether the grave is on a north slope or a south slope, will influence the colonization rate. Often the plants that initially invade the disturbed area are the same plants that invade other disturbed areas in the vicinity — such as road cuts or overgrazed areas — and frequently they will be different species from those in surrounding, undisturbed areas. These new, colonizing plants can include many species — such as thistle, cheat grass, and kudzu — that are able to root quickly because the soil in the grave has recently been aerated.
Because the soil in the grave is aerated, it is less dense than in the surrounding area. Therefore, methods such as ground penetrating radar, infrared detection, and electromagnetic techniques may be of some help in finding an area after the surface indicators are fading. Even though years may have passed since a body was buried, the soil within a grave can remain less dense and can have different conductivity values than the surrounding soil.
Additional search techniques may be used as well, depending on environmental situations and on the experts who are available in the area. For instance, highly trained detection dogs may be used to assist in locating remains. However, the standard pedestrian search is the technique most often used. Searchers, who are experienced in recognizing the clues, walk an area in a straight line in a way that the area searched by their eyes overlaps the area searched by the individuals walking next to them. If one person sees a clue, the entire line stops until that area is flagged for further investigation or until the item or area is determined to be insignificant.
Obviously, great care must be used in recovering remains from a grave. Exhuming the body destroys the context within the grave, so one must be proficient in recording all of the bits of evidence, including the precise locations of evidence. All of this seems obvious, but there are countless examples of law enforcement agents, and even archaeologists and physical anthropologists, moving too quickly through a grave exhumation and missing important contextual information.
Modified archaeological techniques are often used to accomplish this task. Archaeologists usually establish a grid system over an area to be excavated and often over an area where remains were scattered on the surface. The excavation takes place within each grid (usually 1 meter square), and all of the dirt removed from each level within the grid is screened. In this way, even if the archaeologists miss an item in situ (in its original location), at least some locational information will be recovered as it is screened. As each item is uncovered, it is given a number, its location is mapped (using vertical and horizontal coordinates), and it is photographed.
Who picks up and records the evidence at a scene? Technically, anyone can do this, as long as proper chain of custody requirements are met. The chain of custody is fulfilled with a series of documents which record who had control of material, when it was received, when it was released to another individual, and what was done to the material at each step. This documentation is important so that each side in a court case knows exactly how the evidence was processed, by whom, for what reasons, and how the various procedures may or may not contribute to solving the crime. Often the anthropologist will help locate and uncover the evidence at the scene and let the law enforcement crime scene technician actually recover the evidence to reduce the number of links in that chain. The anthropologist is not removed from the chain by doing this — his or her involvement is recorded in the crime scene logs. Also, if, for instance, a specific test is performed on a piece of evidence, that test must be documented. In fact, everything must be documented. If, for example, a forensic anthropologist is to study a set of remains and if a bone is nicked with a scalpel during autopsy, that damage must be documented by the forensic pathologist so that the anthropologist will not mistake it for damage potentially caused at or about the time of death.
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Case A A man's decomposed body was discovered in a rural area. The sheriff's officers, who responded to the scene, suspected that the individual was the victim of homicide because of the obvious damage to the clothing and to the body underneath. It appeared that the shirt had numerous cuts. The body was transported to the local medical examiner's office for an autopsy, while the area that was around and under the body was searched for evidence. |
The forensic anthropologist was called to the medical examiner's office so that she could attend and then participate in the autopsy. Forensic anthropologists work as a team with the forensic pathologist, forensic odontologists, forensic radiologists, and all other forensic experts. In this case, the forensic pathologist performed the autopsy, which was somewhat modified because of the extensive decomposition of the body. Because the evidence that forensic anthropologists need is usually obtained from the skeleton, their work usually starts after the pathologist is finished. The soft tissue is usually removed from the skeleton so that the clues are more obvious.
In every step of the way through the search and recovery and also throughout the laboratory analysis, the forensic anthropologist is aware of, and is working toward, fulfilling an incredible set of responsibilities. This was once a living person, and there are very few professionals who are trained to tell his or her story. It is important to provide information so that the family members of the victim can have the answers they seek concerning the circumstances surrounding the death of that individual. It is equally important that the anthropologist be prepared to go to court with the findings.
The investigation of the identity of human remains must begin with a determination of whether or not the remains are human. If the remains are not human, the case usually ends, although the author has been asked to continue on cases in which, for instance, a dog had been shot. In this case, the shooter claimed that the dog was attacking him. The direction of travel of the bullet was important in this case, as the dog was not facing the man when he was shot.
After the remains in question are determined to be human, the
next question is usually sex determination, as this eliminates approximately
50% of the reported missing individuals from further consideration. Because
skeletal differences between males and females are not fully established until
puberty, sex determination is very difficult and unreliable in very young individuals.
Consequently, the techniques used to establish sex are approximately 60% to
70% accurate in very young individuals.
After puberty, males are usually bigger than females. The bones are larger overall
and the areas devoted to muscle attachment are larger and more rugged, just
as in other primate species — for example, gorillas and orangutans —
and in many other mammals. This difference is what has been defined in the textbook
as sexual dimorphism. However, in order to utilize this size difference in sex
determination, the researcher must be able to identify the population from which
a skeleton came, as populations differ greatly in average skeletal size and
degree of sexual dimorphism and proportions. For example, populations native
to India usually have smaller skeletons and exhibit less sexual dimorphism than
Australian Aborigines. An adult male Asian Indian skeleton placed alongside
a male (or many females) adult Australian Aborigine skeleton would, if judged
on the basis of size, be misclassified as a female. A study performed on humeri
of Arikara vs. Pueblo (North American Native groups) misclassified almost 70%
of the male Pueblo humeri on the basis of size alone. This indicates that size
differences between these two populations could easily confuse sex differences
(France, 1983). For this reason, morphological differences are usually more
reliable than are general size differences, particularly if one is not sure
from what population an individual is derived.
Another complication can arise from cultural practices, since variability in
muscle use can also reduce the reliability of skeletal indications of sex. For
instance, a female who lifts heavy weights will have upper arm measurements
that are closer to her male counterpart, particularly if he sits behind a desk
and does no heavy lifting. Likewise, in a culture in which burden baskets are
carried on the female heads, the size of the mastoid process of the cranium
will increase so that a population would show less dimorphism for that trait.
The most reliable skeletal area for the determination of sex is, as one might guess, the pelvic girdle. As is easily remembered, the sex differences are greatest in this area because the female pelvis is shaped differently to accommodate the needs of childbearing. Several areas of the pelvic girdle show these differences (see Figures 1a and 1b).
Figure 1a Female pelvic girdle
Figure 1b Male pelvic girdle
It has been widely taught that the second best area for sex determination is the cranium (see Figure 2). Measurements of the postcranium, while important, should be the basis for sex estimation only when the cranium and pelvic girdle are not usable. When the entire skeleton is available for inspection, the other areas of the skeleton should not be ignored, even though the pelvis is present. Always remember, the more information gathered, the better. In fact, if one knows the population from which a skeleton is derived, postcranial measurements can be highly reliable. Some researchers report an accuracy rate of over 90% in some measurements (cf. Krogman and Iscan, 1986; Dittrick and Suchey, 1986; France, 1983) (see Table 1). For a more thorough discussion of some of the techniques being studied, consult Krogman and Iscan (1986).
Figure 2 Male (left) and female (right) skulls
Table 1 Table of some metric determinants of sex
| Maximum Head Diameter of Femur (in mm.) | |||||
| Population |
Sex
|
N
|
Mean
|
S.D. Cutoff
|
Correctly Classified
|
| African Americans(Tennessee Data Bank) |
M
|
70
|
48.0
|
>=46.0
|
84%
|
|
F
|
40
|
42.4
|
<=45.0
|
90%
|
|
| European Americans (Tennessee Data Bank) |
M
|
150
|
49.0
|
>=46.0
|
92%
|
|
F
|
100
|
42.4
|
<=45.0
|
93%
|
|
| Native Americans (Central California Combined Horizons) |
M
|
175
|
47.0
|
>44.6
|
88.7%
|
|
F
|
171
|
42.2
|
<44.6
|
||
| Central California Combined Horizons (Early Horizon, beginning circa 2500 B.C. through Late Horizon beginning after 500 A.D. from Dittrick and Suchey, 1986). | |||||
| Maximum Head Diameter of Humerus (in mm.) | |||||
| Population |
Sex
|
N
|
Mean
|
S.D. Cutoff
|
Correctly Classified
|
| African Americans(Tennessee Data Bank) |
M
|
70
|
47.4
|
>=45.0
|
86%
|
|
F
|
40
|
40.8
|
<=44.0
|
91%
|
|
| European Americans (Tennessee Data Bank) |
M
|
150
|
49.0
|
>=46.0
|
89%
|
|
F
|
160
|
42.3
|
<=45.0
|
93%
|
|
| Vertical Head Diameter (in mm.) | |||||
| Population |
Sex
|
N
|
Mean
|
S.D. Cutoff
|
Correctly Classified
|
| Native Americans Pecos Pueblo |
M
|
86
|
43.4
|
>=41.0
|
91.6%
|
|
F
|
69
|
37.9
|
<=40.0
|
||
| Native Americans Arikara |
M
|
93
|
46.7
|
>=44.0
|
90.5
|
|
F
|
86
|
41.2
|
<=43.0
|
||
| From France, 1983 | |||||
From these photographs, what is the sex of the individual in
Case A (see Figures 3, 4, and 5)?
(The answers to this question, and other questions will be revealed at the
end of the module in the resolution.)
Figure 3 Left pubis from Case A
Figure 4 Right greater sciatic notch from Case A
Figure 5 Cranium from Case A
Several methods are commonly employed in the determination of the physiological age of a skeleton. Researchers hope that the physiological age will give an accurate estimate of chronological age, but environmental, nutritional, and disease stresses will often cause changes in the skeleton which will mask the true age of the individual. Dental formation and eruption times are less affected by insults, such as disease and nutritional deficiencies, than are the formation and maturation of the bony skeleton. Therefore, where appropriate, these dental criteria are more reliable age determination techniques. Because of variation in disease and nutritional effects, the diagnosis of age in a skeleton will always be represented as a range, as the physiological age can span several chronological years.
The most appropriate specific age determination technique applied to a skeleton depends on the general age category of the skeleton. If the individual is relatively young, dental formation and eruption times are the most accurate means of identification. The determination of the ages in which the deciduous and permanent dentition erupts is useful in identifying age to approximately 15 years (see Figure 6). The third molar (wisdom tooth) erupts after this time, but the age of eruption is so variable that it is, by itself, not a very reliable age indicator. There is also the possibility that the tooth may never erupt.
Figure 6 Dental age determination chart (courtesy Douglas Ubelaker)
Even though bone growth occurs concurrently with dental development and eruption, it is not as reliable as an age indicator. Of course, there are times when no dental evidence is available, so it is important to know about bone growth.
Bone Growth
Postcranial bones, except for the clavicle, are formed initially in cartilage — that is, a cartilage model precedes actual formation of bone. In addition, several bones of the cranium are formed from cartilage models. Depending on the bone in the body and at different times during growth, osteoblasts (bone-forming cells) invade the cartilage to lay down bone. The ossification centers are the points at which this initially occurs in each bone. The diaphyses (singular = diaphysis) (primary centers of growth) are responsible for most of the length of long bones. The epiphyses (singular = epiphysis) (secondary centers) are separated from the diaphyses by metaphyses (singular = metaphysis), which are thin layers of cartilage being sequentially overtaken and replaced by bone. The metaphysis is the actual site of bone growth. When the diaphysis meets the epiphysis, the metaphysis disappears, the ends of the bones fuse, and the longitudinal growth ceases. Because this epiphyseal closure occurs at different times in different bones, the age of an individual can be determined by which epiphyses have fused and which have not. Figures 7 and 8 show an epiphysis and diaphysis which have not yet fused. Notice the characteristic undulating appearance of the unfused surfaces of bone.
In evaluating a fully adult skeleton in which the teeth are erupted and all epiphyses are united, it is necessary to look at developmental and degenerative changes in other parts of the skeleton. At one time the ages at which the cranial sutures (the areas separating the bones of the cranium where growth occurs) become obliterated was used quite extensively. However, with more research, the ages of suture closure were found to vary widely, making this technique unreliable in the precise determination of age. In addition, endocranial sutures (the sutures as seen inside the cranium) are often difficult to see and interpret in intact crania.
However, a review of a sample of crania from people (144 males and 51 females) of various ancestries from the Los Angeles Coroner's Office (Baker, 1984) indicates the following general guidelines:
Endocranially:
1. If all sutures are completely open, the individual is less than 36 and usually less than 27.
2. If all sutures are completely closed, the individual is 26 or older.
Figure 7 Epiphyseal surfaces from left femur and its distal
epiphysis
Figure 8 Distal epiphysis from femur in proper position
Pubic Symphyseal Face
The pubic symphyseal face (where the two pubic bones are joined through cartilage in the front of the pelvic girdle) in a young individual is characterized by an undulating surface, such as seen on a normal epiphysis. But it undergoes relatively regular changes from age 18 onwards. Several researchers have developed age determination techniques based on the changing morphology of the symphyseal face. Earlier systems (Todd, 1920; McKern and Stewart, 1957) have been largely replaced by a system using a more modern, representative sample (the Suchey-Brooks system). This is a six-phase system based on a large sample of individuals for whom legal documentation of age is provided by death certificates. This autopsy room sample, comprised mostly of individuals born in the United States and Mexico, is more representative of the general population than was true of previously used samples.
Figures 9a and 9b show the key features distinguishing the pubic symphysis phases in both males and females. Note from the photographs that, at very young ages, the surface of the pubic symphysis somewhat resembles a young epiphyseal surface. As the individual ages, this surface and the surrounding aspects of the bone proceed through regular changes until at old age it presents a more porous bone, sometimes with spicules of bone growing away from the surface. The pubic symphysis of both females and males go through similar phases, but the exact nature of these changes can be altered in several ways (see Table 2).
Figure 9a Male pubic bone age determination (courtesy
Judy M. Suchey)
Figure 9b Female pubic bone age determination (courtesy
Judy M. Suchey)
Table 2 Descriptive statistics related to the Suchey-Brooks pubic age determination system
|
Female
|
Male
|
|||||
|
Phase
|
mean
|
S.D. |
95% range
|
mean
|
S.D.
|
95% range
|
|
I
|
19.4 |
2.6
|
< 24
|
18.5
|
2.1
|
< 23
|
|
II
|
25.0
|
4.9
|
19-40
|
23.4
|
3.6
|
19-34
|
|
III
|
30.7
|
8.1
|
21-53
|
28.7
|
6.5
|
21-46
|
|
IV
|
38.2
|
10.9
|
26-70
|
35.2
|
9.4
|
23-57
|
|
V
|
48.1
|
14.6
|
25-83
|
45.6
|
10.4
|
27-66
|
|
VI
|
60.0
|
12.4
|
> 42
|
61.2
|
12.2
|
> 34
|
These are intended to be brief introductions of this system. For the complete information on the system, please consult Suchey and Katz, 1998.
Rib Phases
The changes experienced by the rib are similar in some ways to those changes in the pubic symphysis. Iscan, et al. (1984, 1985) have selected and illustrated specific phases for age-related changes in the sternal end (anterior, near the sternum) of the fourth right rib. In the earliest phases, the surface which articulates with the sternum is flat or billowy with a regular rim and rounded edges. The bone itself has a young appearance. As the individual ages, the center of the face is indented relative to the edges, and this indentation increases throughout the life of the individual. The rim become less regular in shape, and spicules of bone project from the edges. The bone becomes more porous and brittle as the individual becomes older.
Old Age
Basically, the developmental changes which characterize young skeletons give way to the degenerative changes of old age. Arthritis (see the changes in Figure 10) becomes more prevalent and pronounced, as does osteoporosis (increased porosity of the bone, particularly in post-menopausal women). These changes can give corroborative evidence to determinations of older age, but are not reliable by themselves, as injury and disease can lead to many of these changes in the skeleton.
Figure 10 Degenerative joint changes in tibia at knee
Dental Attrition
The amount of attrition on teeth has been traditionally used to determine the relative age of individuals within a population. It should be stressed, however, that humans eat a variety of foods which promote enamel attrition at different rates. Consequently, dental attrition should not be used to determine the absolute age of an individual, particularly when the dietary and other uses of the teeth in that individual are not known.
What is the age range of this individual in Case A (see Figure 11)? Notice that a range is requested. It is inappropriate and impossible to give a specific age in these cases because of the range of human variation, in addition to nutritional and health differences between individuals of the same age.
Figure 11 Pubic symphysis from Case A
A controversy in anthropology exists today over whether or not "races" exist. For centuries peoples in the world have been categorized into groups, the most recent titles being Caucasoid, Negroid, Mongoloid, and usually Australoid and Polynesian. (See text for further discussion.)
There are many reasons to discontinue the use of racial terminology for humans. The terms used — as well as the identification of differences between groups in general — have made it easier in history for groups of people to attempt to demonstrate that they are more intelligent, more fit physically, and more deserving of the benefits of society than those individuals who are different. Racism has used these terms as its tools.
Racial terms place people in pigeonholes even when they do not physically fit. It is generally recognized, and often stated, that there is more variation within races as they are usually defined than between racial groups. There is a continuum in each of the traditional polygenic characteristics — such as skin color, hair form, etc. — which makes it impossible to categorize every individual in the world into rigidly defined racial groups. Thus, it is more accurate to investigate traits as clines instead of absolute defining characteristics. (See text.)
Forensic physical anthropologists, however, would be derelict in their duty if they ignored the morphological differences which can help to identify an individual. When an anthropologist is asked to assist in the identification of a parcel of bones, part of that identification must include a statement as to probable ancestry or "race," because this feature is included in the social identity of that person. This identity was traditionally made in racial terms and was usually made by the person him- or herself. This identification of ancestry, however, is changing, in that more of the world's inhabitants are identifying themselves according to the geographic or political location of their ancestors — i.e., German or Spanish or Bosnian instead of Caucasian or even European. The question for forensic physical anthropologists then becomes, How closely can we estimate these more refined identities from the physical remains? The answer is, It depends. If a person identifies himself as an African American, it implies that his recent ancestors were from Africa but that he is currently living in America. The forensic anthropologist, of course, cannot determine the person's current place of residence by the bones alone, so perhaps we would be misleading the law enforcement official if we say that this is an "African American." However, it is becoming more feasible to determine, with experience, the probable ancestral background with more refinement, even to the point that many forensic anthropologists can determine the regional ancestry of many Native American groups by looking primarily at the facial morphology. Many forensic physical anthropologists are now stating in their reports that, for instance, the remains are from an individual with European ancestry, or with African ancestry, or even with western African ancestry.
One thing must be stated, however. Even as forensic physical anthropologists are becoming more skilled in their abilities to detect clues about ancestry in the skeletal morphology, it is important to realize that no matter what terms are used to describe the individuals we study, those terms, also, will initiate objections if they are misused. If any term is used maliciously or with intent to create a political hierarchy between recognized groups, its use will increase suspicion and ill will between peoples. Reputable forensic physical anthropologists want the terms they use to be clues to the eventual identification of remains and nothing more.
In the final analysis, students must decide not only the appropriateness of the terms used, but also whether or not it is legitimate and useful to have a group of scientists endeavor to determine the identity of unidentified human remains and to allow them (and you) to develop better methods of determining ancestry. Without that tool, forensic physical anthropologists are less well equipped to help in that identification process.
Figure 12 European American cranial features (courtesy
J. S. Rhine)
Figure 13 African American cranial features (courtesy
J. S. Rhine)
Figure 14 Native American cranial features (courtesy J.
S. Rhine)
What is the probable ancestral background of the individual in Case A (see Figure 15)?
Figure 15 Cranium from Case A
Estimates of living stature from the skeleton are a routine part of the analysis of remains, but they are not very precise. Therefore, they should never be used alone in establishing identity. An example in which stature reconstruction becomes more important is in sorting of commingled remains — that is, remains of several people where it is more difficult to sort the remains into individuals again. In a simple situation with two individuals, one tall and one short, it is a relatively simple matter to sort the remains by stature.
The ability to apply a face to a skull is dependent on the ability to predict the thickness of soft tissue on the face. In early studies the thickness of the soft tissue of many individuals was measured as soon as possible after the person had died by inserting a pin into standard locations and measuring that thickness directly. Today tissue thickness is measured using ultrasound on living individuals. Not only is this technique an improvement esthetically, but more importantly it is an improvement as the soft tissue has not had a chance to lose its tone.
Facial approximation is typically used only after other methods for identification have not yielded results. A face is applied to the skull either in clay or with two dimensional drawings or computer renderings. That rendering is placed in newspapers and on television in the hope that it will trigger someone to call law enforcement and say something like "That resembles Uncle Joe who disappeared two years ago." At that point, the antemortem (before death) medical and dental records, and perhaps DNA samples, for Uncle Joe are obtained, and experts decide if these are the remains of Uncle Joe.
Occasionally a skull is compared photographically to antemortem photographs of the suspected victim. Usually the photograph of the person is videotaped with one camera while the skull is videotaped with another video camera, and the two video feeds are digitally mixed to perform the superimposition. Of course, it is important that the skull be in the same plane as the photograph, otherwise, even if it is a positive match, the superimposition will not match. This technique should not indiscriminately be used as a means of positive identification. Even with the best equipment and the best results, there is still about a 10% chance that with one view there will be a positive match even when the two images are not from the same individual.
Many mechanical forces and disease processes leave their marks on bone. Large volumes are dedicated to the study of these conditions, but we will view only a few of them here. It is important to note, though, that while forensic anthropologists can describe and diagnose many of these forces and disease processes, they cannot (by law) determine cause or manner of death. This is the responsibility of the coroner or medical examiner.
Mechanical Forces
Many types of mechanical insults — such as, cut marks and sharp force injuries, blunt force trauma, gunshot wounds, and others — are seen by forensic physical anthropologists, pathologists, archaeologists, and medical examiners. Obviously, some injuries are combinations of two or more of these categories. For instance, sharp force injuries — such as saber cuts or hatchet cuts — include the cutting action of the sharp end of the implement and, also, the impact forces released as the weapon strikes the bone. Victims of plane crashes or building explosions sometimes exhibit many different types of forces.
Bone is elastic in life and can "bounce back" from many mechanical forces, particularly if the force is slow to build and contains little power. However, if a great deal of force is quickly applied, bone will fracture before it has a chance to exhibit its elastic qualities. Slow-loading or slower-impact forces produce more elastic response from bone before it fractures. Fracture lines usually radiate away from the point of initial impact, hence, they are called "radiating fracture lines." Radiating fracture lines from multiple injuries usually do not cross each other, but they stop at other fractures or cranial sutures. Depending upon the degree of force and the area in bone, concentric rings may also radiate away from the point of initial injury (likened to dropping a pebble in a pond). They are also helpful in identifying the initial point of contact with bone. In contrast, trauma to dry bone usually results in fractures with ragged edges and without the radiating fracture lines or concentric rings. Thus, these fracture patterns are also crucial in distinguishing fresh bone injuries from dry bone damage.
Blunt Force Trauma
Blunt force trauma is as its name implies, damage caused to bone by objects with relatively broad surfaces as opposed to a sharp instrument. This type of injury usually results from a relatively slow-loading force and can cause significant plastic deformation of the bone before the bone fractures. Blunt force trauma often results in the separation of wedge-shaped fragments of bone, as bone can withstand compression forces to a greater degree than it can withstand tensile forces (those which pull bone apart) (see Figure 16 for example). See Figure 17 for an example of blunt force trauma in the human occipital bone.
Figure 16 Diagram of forces in bone
Figure 17 Blunt force trauma in cranium
Cut Marks
Cut marks are caused when a sharp object incises bone. Upon close inspection with a dissection microscope or scanning electron microscope, cut marks typically have a "V" shape or a series of "V" shapes — such as made by stone tools which have a series of parallel cutting edges along the worked edges (see Figure 18). Vascular grooves (channels in bone through which blood vessels pass, most often the grooves along the lateral aspects of the frontal bone) are often mistaken for cut marks, but they have a rounded or "U" shape in cross section. Rodent tooth marks can also be mistaken for cut marks, but typically they are paired and have a square cross section (see Figure 19). Sharp force injuries that combine cut marks with force often leave a "V" cross section with compacted bone near the center of the cut that is frequently lifted and has somewhat displaced edges.
Figure 18 Scanning electron micrograph of cuts made from stone tool. Notice
parallel striations
Figure 19 Rodent tooth marks on bone
Gunshot Wounds
Gunshot wounds are produced by bullets of different size (caliber) and are projected by a wide range of explosive force. They are somewhat predictable in that the missile usually creates a round opening, depending on the degree of wobble and tumble in the bullet. This is smaller at the initial point of impact of the bullet to the bone and larger at the point of exit from bone. In this way the direction of travel can often, but not always, be determined by looking at the direction of beveling in the bone (see Figures 20 and 21).
Figure 20 Gunshot entrance wound
Figure 21 Gunshot exit wound
Healing of Bone
How does one determine whether or not an individual has survived a mechanical insult to bone? In all of the above examples, the edges left by the insult are sharp. Bone reacts to fractures by immediately forming a callous around the point of fracture. This callous is initially soft tissue but is replaced quickly by deposits of bone, which are thereafter remodeled into sturdy new bone. The process of formation of loosely woven bone stabilizes the fracture within weeks, depending upon the age and health status of the individual. The remodeling process continues until all woven bone is replaced by dense bone tissue. If the bone is properly set, it should be nearly identical to its condition prior to fracture. In cases where fractures are not properly treated, there can be considerable deformity (see Figures 22 and 23).
Figure 22 Healed displaced fracture of tibia
Figure 23 Healed displaced fracture of tibia, longitudinal
cut view
(courtesy Armed Forces Institute of Pathology, National Museum of Health and
Medicine)
Disease Process
It is often very difficult to diagnose the specific pathogen responsible for disease changes to bone, as bone can react to the entire disease spectrum in limited ways — i.e., the addition of new bone and/or the destruction of existing bone. Because evidence of disease and/or trauma can greatly assist in the identification process by comparisons with medical records, experienced anthropologists and pathologists will describe the changes seen in the entire skeleton. Remember that it is more important to accurately describe the bony changes you see than to diagnose the specific pathogen responsible for those changes. As we learn more about disease processes in bone, the diagnosis may change, but the description most likely will not.
Describe the damage to the body in Case A. In your opinion, what could have caused the damage shown in each photograph? Note that there may be different "tools" used in each case. (Use Figures 24 through 29 for your analysis.)
Figure 24 Cranium from Case A
Figure 25 Ribs from Case A
Figure 26 Pelvic girdle from Case A
Figure 27 Occipital bone from Case A
Figure 28 X-ray of cranium from Case A.
Notice spot of radiopaque substance at arrow
Figure 29 X-ray of ribs from Case A
Resolution of the Case
Case A: According to the evidence and to eyewitness reports, this individual, who was a 45 year old male of European ancestry, was attacked and robbed by several teenagers. They later confessed to stabbing him multiple times with a knife, and then, after he had fallen, shooting him in the chest. As they were driving away, they ran over the victim twice with a car.
As can be seen, however, one part of their story is not supported by the evidence. There is no evidence of a gunshot wound in the chest by the gross morphology of the bones of the chest — i.e., there are no round holes with beveled edges. In addition, as the bullet passes through bone, it often leaves metal "smears" on the bone which can be seen by x-ray. There are no metal "smears" on the bones of the chest in this victim.
However, a gunshot wound can be seen on the left frontal bone. This is a classic "keyhole" fracture in which the bullet enters the bone tangentially, and, because the skull is rounded, exits the skull close to the entry. The combined hole then has beveled edges on both the inside and the outside of the bone!
Because of the angle of this wound, it is logical to assume that part of their story is true. The victim probably was already on the ground when shot. According to the story, although the shooter was aiming for the chest, the bullet went off its mark and struck the head.
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With the continuing popularity of forensic programs on television and in the popular press, more students want to pursue careers in forensic physical anthropology. Moreover, by taking an introductory physical anthropology class or a more advanced course, some students are stimulated to begin thinking seriously about pursuing a career in this field. There is an array of career possibilities within the forensic sciences as broadly defined. Some of these career paths can be effectively pursued with a bachelor’s degree, while other more specialized careers (discussed below) require more advanced training. For example, students who have begun with an undergraduate forensic anthropology orientation have gone on to careers as regular police officers or as detectives. Others have obtained positions as autopsy technicians in coroner’s offices, and several have pursued related careers in biomedicine as physician’s assistants or as medical doctors — many of these needing advanced degrees. Numerous opportunities as a forensic specialist exist in crime laboratories. Usually this requires considerable academic course work and significant training in chemistry — i.e., at least the equivalent of a bachelor’s degree and, ideally, a master’s degree in chemistry. A full-time professional position is the most romanticized career path associated with forensic physical anthropology. This would be an expert who works closely with law enforcement personnel and testifies routinely in court. Such positions, however, are extremely scarce and, understandably, require much advanced training as well as demonstration of competence. Forensic physical anthropologists, who wish to be professionally established at the highest level, must become certified as an expert by the American Board of Forensic Anthropology. In order to gain such board certification, one must first have a doctoral degree in physical anthropology, be working in the field for three years, and be invited to sit for an eight hour examination (both written and practicum). Presently, not all individuals who identify themselves as forensic anthropological experts are board certified; although almost all have at least a master’s degree and several years of experience. Moreover, the vast majority of practicing experts never obtain full-time positions. Most forensic anthropologists consult part-time while simultaneously pursuing parallel careers, usually as university professors. Finally, most experts — whether board certified or not — are members of the physical anthropology section of the American Academy of Forensic Sciences. This professional organization also has sections in engineering, jurisprudence (law), psychiatry, pathology/biology, odontology, criminalistics, questioned documents, and toxicology. There is also a general section for those experts who are not members in any of the above mentioned fields. In order to be a member of the physical anthropology section, one must have at least a master’s degree or must be working toward a graduate degree. For more information about this organization, contact:
Currently, only a few universities offer doctoral programs with an emphasis in forensic anthropology. Most practicing forensic anthropologists hold doctoral degrees in physical anthropology with concentrations in osteology. They then gain experience in forensics with someone who is working in the field. Also, classes in anatomy, physiology, and physics are useful in calculating how bone reacts to different forces. For more information about the colleges and universities offering graduate degrees in physical anthropology, go to the reference section in your library or access specific university programs on the Internet. |
Acknowledgements
Lynn Kilgore and Robert Jurmain offered helpful editorial suggestions, and
Judy Suchey gave helpful recommendations about pubic age determination.
Most of the techniques that describe how to locate clandestine graves relate
to work done by NecroSearch, International. You can learn more about this group
by visiting the web site: www.necrosearch.org.
