1.1 “Forensic anthropology is the application of the science of physical anthropology to the legal process.”
Forensic anthropologists provide services to a large community, which includes a variety of law enforcement agencies, from local to federal or even international jurisdictions, medical examiners, coroners, and others charged with the responsibility for the investigation of death.
In these endeavors forensic anthropologists cooperate with odontologists, pathologists, radiologists, and other forensic specialists who deal routinely with human remains. In the fourteen years since the eminent William R.
Maples scribed the initial version of this chapter, forensic anthropology has experienced a dramatic increase in visibility within the popular culture as a result of media depictions, some fanciful, others accurate and informative. The increasing contributions of forensic anthropology, from unidentified remains cases and homicide investigations to transportation and natural disasters to crimes against humanity, have been best described by its practitioners.
As public awareness of forensic anthropology has increased, so has the number of board-certified diplomates, currently about seventy-seven, and the number of institutions offering advanced degrees in forensic anthropology, or physical anthropology with a forensic emphasis.
In the 1970s most practitioners of forensic anthropology held academic positions and offered only occasional assistance to investigative agencies. Once rare, forensic anthropology service laboratories affiliated with universities are no longer unusual.
Some organizations employ a number of full-time forensic anthropologists (e.g., Joint POW/MIA Accounting Command/Central Identification Laboratory [JPAC/CILHI], National Transportation Safety Board [NTSB], and private disaster management corporations), and an increasing number of large medical examiner establishments employ full-time forensic anthropologists.
Consequently, the presence of forensic anthropologists providing case reports, depositions, and expert testimony in civil and criminal courts and in tribunals around the world has increased dramatically in the past two decades.
1.2 Typical Case Progression
Cases requiring the services of forensic anthropologists arise in a variety of ways. Excluding mass fatality scenarios, the appearance of unknown human remains may involve skeletal components and scavenged fragments scattered about the landscape, clandestine burials, submerged remains, or the occasional skull upon a mantel kept as a memento mori discovered incidentally during execution of a warrant for an unrelated cause. Anthropologists are increasingly summoned by arson investigators for in situ examination and recovery of fragile remains prior to transport.
When remains come to light, law enforcement may have a theory about the identity of the decedent, or perhaps about the manner in which the decedent came to an end. In such cases, someone may be missing from the community, and circumstances lead investigators to believe that the remains might be that individual. Additional information about the putative cause or manner of death may also have been developed. In such instances, experienced forensic anthropologists will follow something akin to the null hypothesis approach.
As the examination progresses, the anthropologist attempts to defeat or disprove the a priori theories offered. In this way, the careful examiner avoids any inclination to notice only the data that support the favored theory while ignoring observations that might not fit the official mindset.
When remains are presented to the anthropologist with no background information whatsoever, the task is to perform the most thorough examination possible with the materials available. In some instances an anthropologist may be asked to examine a skull, a set of postcranial remains, or some skeletal component when additional remains are actually available. Experience dictates that the better course of action is to insist upon examining all of the materials available. In this way, the most complete and consistent report may be rendered. This approach is particularly important when the remains may be reexamined by subsequent investigators. If additional case-related remains emerge during the course of investigation, these should be immediately made available to the original examiner.
1.2.1 Animal vs. Human and Minimum Number of Individuals
The first steps in examination of skeletal remains will usually be determining whether the specimen is animal or human, and if so, how many individuals are represented. Differentiating animal remains from human remains usually amounts to an examination of the epiphyses of long bones, or simply the recognition of a particular species as itself based upon the examiner’s skill as a comparative osteologist. In practice, this task usually devolves to the usual suspects, i.e., bear, pig, turtle, primate, or some species of bird, for the latter are often confused with fetal bones by unskilled observers. When fragments reveal little or no distinguishing anatomy, the examiner may resort to histological/microscopic means or other distinguishing physical or chemical properties (Stewart 1979, 45-58). If it is necessary to go beyond simply stating that a specimen is nonhuman, comparative skeletal atlases, some region specific, are readily available for those willing to do the necessary taxonomic keying.
On occasion, the anthropologist is presented with a specimen such as a small amulet or other artifact that is allegedly made of human bone. The author recalls a scrub stone said to have been made from the “compressed sweepings from the ovens at Treblinka.” On another occasion,
the artifact was a small crucifix supposedly “carved from a human femur” in one of the Nazi death camps. In the first instance, x-ray fluorescence and mass spectroscopy revealed a combination of artist’s plaster and charcoal.
Under microscopic examination, the crucifix proved to be of walrus ivory, and probably produced from a die. Based upon conversations with several colleagues, there is apparently a significant prevalence of pseudobone objects driven by underground marketing of “holocaust” artifacts. Anthropologists in university settings will find an array of analytical equipment and techniques applicable to these problems no more distant than a phone call to a colleague in the chemistry or physics department.
1.2.2 Minimum Number of Individuals
Determining the minimum number of individuals represented in a collection of bones usually requires looking for duplication of a component (e.g., two left humeri, two right upper third molars, etc.) or excessive asymmetry between paired components that cannot be explained by pathology, e.g., developmental or traumatic stunting. Here it is important to recognize that attribution of some bones may be challenging, e.g., digits, sesamoids, etc., and that the human skeleton presents an impressive number of normal variations—more or fewer cervical and lumbar vertebrae, presence of cervical ribs, etc.
On more than one occasion a forensic anthropologist has received skeletal remains that may have become commingled on a shelf after many years of storage. In some cases, evidence custodians clearing out old specimens have unintentionally associated components from different individuals in a box or other container that is then presented to the anthropologist as the remains from a single case. The author was once cautioned by a forensic pathologist who worked in Hawaii that “an extra patella” in a skeletal submission might not be surprising since many traditional Hawaiians carried one as a good luck object!
Statistical statements may be needed to support a conclusion about the minimum number of individuals. This is particularly likely when there is a reasonable probability that a set of recovered remains may be commingled.
Given a total number of bones that can be precisely identified as to their exact location in the skeleton, and the number of bones in that category actually found in the sample, the probability of commingling can be calculated by hand.
1.2.3 Medicolegal Significance of Human Remains
Not all human skeletal material that comes to light is of forensic significance. Law enforcement personnel, road construction crews, and others have occasionally encountered buried human remains from archaeological contexts. These have ordinarily undergone sufficient taphonomic modification, e.g., loss of collagen, diagenesis, exfoliation, etc., that their antiquity is evident. Techniques for establishing the postmortem interval for long-dead remains, ranging from gross inspection to physical and chemical methods, have been described ably elsewhere.
Remains of historic or contemporary age may be accidentally unearthed when the locations of private cemeteries are unknown or have not been properly recorded, or when ground markers have been removed or have fallen into ruin. Such interments can usually be easily distinguished from coffin parts, embalming artifacts, etc., and are of no forensic significance, although such events may occasionally give rise to civil proceedings.
1.2.4 The Biological Profile
Having certified that a known number of sets of human remains are at hand, the forensic anthropologist establishes a biological profile. This is a qualitative and biometric description of the remains that, ideally, includes, in order, a diagnosis of sex, ancestry (population membership), skeletal and dental age, and a description of stature and physique. The biological profile may be complete or partial, tentative or robust, depending upon the developmental status (i.e., child, adult, etc.), quality, and quantity of the remains and the skill of the investigator. As the biological profile is constructed, the anthropologist will typically enumerate any additional features that might be used as unique identifiers, e.g., old injuries, embedded project i les, orthopedic appl iances, congenital or developmental anomalies, genetically determined variations, etc.
Unique identifiers associated with the dentition are best noted and referred to the forensic odontologist, who will perform the case-related charting and comparisons with antemortem records of possible matches that may become available. In the author’s laboratory, standard dental charts and digital bitewing radiographs are made a permanent part of each case file. In this way, information can be transmitted electronically to odontologists around the world for rapid comparison with suspected matches for unidentified remains.
1.2.4.1 Sex
Typically, sex will be determined first. The most reliable diagnostic features are the innominate bones (os coxae) of an adolescent or adult. Depending upon the completeness of the specimen, sex may also be determined from the cranium, long bone dimensions, discrete features, general size criteria, and several discriminant function tests that compare bone dimensions to their means within databases populated by individuals of known sex. It is important to note that a significant number, approximately 5%, of individuals in most populations will be androgynous, i.e., will possess an equal number of male and female skeletal traits (Angel 1985). Natural selection has exaggerated differences in those aspects of skeletal anatomy most closely related to reproduction.
While male pelvic structure is selected to withstand compression, the female pelvis must not only tolerate the compressive loading of loco motion, but also provide the expansibility and protective architecture required by late gestation and the birthing process. Hence, female pelves display flared ilia, a large pelvic outlet, a wide subpubic angle (i.e., the arch formed by the two ischial bones), and sacrum that extends dorsally, increasing the x-sectional area of the birth canal.
Not infrequently, the skull might appear to be of one sex while the pelvic bones indicate the opposite conclusion. In this case, the pelvis is the more reliable predictor of sex. When the sex is judged to be female, the anthropologist will look for evidence of parity. Passage of the term infant
through the canal stretches ligaments transecting the pelvic outlet, resulting in pitting on the dorsal surface(s) of the pubic bones, modification (lipping) of the sacroiliac joint, and deepening of the preauricular sulcus, producing a triad of parity.
Establishment of parturition gains added importance in the era of DNA analyses. Offspring will bear the maternal and paternal nuclear haplotypes as well as the mtDNA signature of the mother, the latter being of added significance when the bones are badly degraded. All determinations
of sex should be accompanied by a statement of statistical confidence of the diagnosis based upon the technique(s) used. The determination of sex in skeletonized fetuses, neonates, and children prior to adrenarche is difficult at best. In these instances, evaluation of the amelogenin locus is the most reliable method.
1.2.4.2 Ancestry
The question here is “How would others have classified the decedent?” as to group, type, race, or some other folk typology during life. From the anthropologist’s perspective, the task is assignment of the decedent to a population or biotype in the biological/genetic sense. In practical terms, this amounts to describing a set of phenotypic characteristics that falls within a folk taxonomy regardless of its biological reality. Complicating the task is the fact that investigative agencies operate within a different vernacular and simply want to know whether the decedent was Black, Hispanic, Asian, etc.—categories that lack any real biological meaning in the genetic sense, but which have found their way into official reporting formats around the world. In current practice, most anthropologists have abandoned the term race in favor of biotype, population, or ancestry, terms that denote as closely as possible the genetic relationship of an individual to a group that shares genes within itself. Close gene sharing (i.e., breeding by distance) produces characteristic average features that might place a living individual within a more broadly, if unscientifically, recognized group. The most difficult cases to assess are those involving admixture, e.g., Negro plus Mexican Indian, or Negroindio;
Amerindian plus French/European plus Negro, or Creole; etc. As in the case of sex, population characteristics are shaped by natural selection. Most of the consistently observable skeletal differences between human populations, e.g., stature, limb proportions, facial characteristics, and the like, are the result of climatic adaptations to the environments in which these populations originally evolved. Thus, bodies with high surface area (e.g., long legs and arms, tall stature, long heads, etc.) should typify original equatorial populations, while those adapted for heat retention (think of Northeast Asians and other arctic indigenes) should have rounded bodies on short skeletal frames with attenuated extremities, rounded skulls, and flattened facial profiles.
Numerous other nonmetric variations can also be associated with populations as allele frequencies for those traits increase as a result of gene sharing within a circumscribed geographical area. Physical anthropologists have described these diagnostic skeletal variations and their incidence within many populations, subgroups, and admixed groups elsewhere.
Metric or statistical assignment of ancestry involves comparisons of measurements from the unknown remains with various means and ranges for the same measurement within collections of known populations. Anthropologists sometimes employ discriminant function tests in which many measurements from an unknown are used collectively to assign a biological distance from the mean values of the same measures in a collection of control individuals of known ancestry.
Such tests usually provide a statement about the likelihood of membership in the reference group. In many instances, various limb proportion indices may strengthen the statistical analysis, and these should be considered when the inventory allows. Finally, no assignment of group membership is complete without reference to nonmetric traits whose incidence within a particular population approaches diagnostic threshold (e.g., os japonicum, shoveled and winged incisors, tertiary third molar anatomy, rocker mandible, etc.). Just as the pelvis is the complex of choice in assigning sex, the skull provides the single most useful set of structures for attribution of ancestry. The dentition, when present, provides an additional rich source of variation to support or refine the assignment of population. Ultimately, the most difficult aspect of the ancestry issue is the translation of detailed and often complex anatomical and statistical findings into common “folk” or other vernacular typologies that usually do not reflect biological reality, or into overly narrow database categories that do not allow for findings of admixture or other useful information. Forensic anthropologists’ reports should include the assignment of biotype, within the limitations of the data, along with any additional information about suspected admixture. Only when the biological population has been described should the findings be translated into more widely used,
if less accurate, descriptive categories.
1.2.4.3 Skeletal and Dental Age
Tissues, organs, and systems mature at different rates. Some undergo renewal throughout life while others decline or disappear altogether under the varying effects of wear, disease, nutrition, and trauma. Attempts to determine the chronological age of a decedent at the time of death by any combination of methods involving the hard tissues will result, at best, in an estimated range. Under ideal circumstances, sufficient materials would be present to allow both osteological and dental approaches to age determination. Dental techniques, reported elsewhere in this volume, should correlate well with skeletal assessments of age in individuals up to around fifteen or sixteen years of age, and should provide reasonably comparable ranges up to about twenty. Because full maturation of the skeleton requires half again as long as the dentition, the former becomes increasingly more reliable as a basis for estimating age. The dentition is the only part of the skeleton that articulates directly with the outside environment. Therefore, the variable effects of diet, disease, traumatic insult, and accessory use are more apt to reduce the value of teeth in determining age in individuals beyond the mid-third decade, and in groups with chronically poor oral hygiene (who tend to appear older than their actual chronological age). The sex and population membership of a decedent must be determined before applying any aging technique because these parameters significantly influence rates of development, necessitating recalibration of the result. The details of osteological aging techniques are beyond the scope of this chapter and should be left to experienced practitioners.
A general approach to determination of age follows:
Fetal period: Estimation of fetal developmental age assumes forensic importance in most jurisdictions because it is usually an indicator of viability. In instances of criminal death of a pregnant individual courts may decide whether to prosecute more than one homicide depending upon the age (i.e., viability) of the fetus. Knowing the age of a discovered fetus may also assist in matters of identification. Usually, diaphyseal lengths may be used in various algorithms to estimate crown–rump length, which may then be translated into lunar age. The timing of appearance of primary and some secondary ossification centers is also of use. Several sources give good accounts of the statistical reliability of various bones and measurements for both gross and radiographic fetal age determination.
Birth to sixteen years: Dental eruption timing and sequence for deciduous and adult dentition are reported elsewhere in this text. As noted, dental and osteological age should correlate well within this developmental interval. In recent years anthropologists and odontologists have
become increasingly aware of differences in rates of skeletal and dental maturation among various populations, and have begun to apply adjustments to their age estimates accordingly.
Also see the dental age estimation link at the University of Texas Health Science Center at San Antonio’s Center for Education and Research in Forensics.
In this interval, anthropologists will make use of diaphyseal lengths, appearance and attachment (fusion) of secondary ossification centers, and the obliteration of some synchondroses.
Radiological age standards have proved useful, especially for the hand and wrist, from early childhood to late adolescence; however, these skeletal components are among the first to be removed by scavengers and are often unavailable.
Sixteen to thirty years: As attachment of primary and secondary ossification centers occurs throughout the skeleton, attention turns to the completion of fusion of these centers. Numerous investigators have established rating scales that describe the degree to which growth
cartilages (metaphyses) have been replaced by bone, signaling the completion of that skeletal element or an articulation.
Likewise, staging techniques have been developed for the ossification of various symphyses, synchondroses, and sutures (e.g., sternal rib cartilages, pubic symphysis, cranial sutures, basilar synchondrosis, etc.). These techniques usually take the form of a semantic differential, which describes changes in the appearance characteristics of a particular structure at known points in time based upon controls.
It is worth noting that the value of a technique is strictly limited by the population sample upon which it is based. Thus, aging techniques must be recalibrated as secular trends (e.g., improved public health measures, available nutrition, antibiotics, etc.) modify maturational rates and longevity.
Thirty years and beyond: As the last epiphyses (usually the medial clavicles) complete development, skeletal age may still be estimated, albeit with increasing error. Unlike the dentition, the skeleton undergoes remodeling throughout life. As a result of endocrine-driven cellular interactions that constantly remove bone and replace it, the skeleton continues to “turn over” approximately every seven to ten years, remodeling itself to accommodate gravity and the mechanical habits of its owner. Alongside this process, the skeletal cartilages that separate and cushion bones undergo increased hardening with resulting grossly observable wear at the articulations, i.e., generalized osteoarthritic changes. Age-related changes in the weight-bearing joints (ankle, knee, hip, sacroiliac, spine, etc.), as well as mineralization of non articular connective tissues (e.g., thyroid, cricoid, arytenoid cartilages, etc.), have been documented along with appropriate caveats having to do with differential effects of lifestyle, disease, and diet.
Other time-dependent structural changes may be appreciated radiographically. For example, as the marrow of long bones assumes a larger part of the hemopoetic burden with age, one can observe an advance of the apex of the marrow cavities in femora and humeri. This is seen as increasing radiolucency toward the proximal epiphyses. This progression has been documented and timed.
Radiographs may also complement and extend developmental staging techniques even after epiphyseal completion by revealing remnants of growth plates that have not yet reached uniform density.
Finally, as skeletal remodeling continues over the course of a lifetime, histological changes in cortical bone may be correlated with age. As old cortical bone is scavenged by osteoclasts to maintain mineral homeostasis, new vascular pathways import osteoblasts that replace it. As the skeleton moves through time, the amount of unremodeled lamellar bone seen in microscopic cross sections of cortex will diminish, and the number of partly replaced structural units of old bone, osteon fragments, will increase. These changes have been documented and calibrated by various authors for a number of sites in the skeleton, and are of use in the aging skeleton because the process of turnover on which it is based extends throughout life. As is the case with other techniques, error in the calculated age range by histomorphological methods increases with time.
1.2.4.4 Stature and Physique
The calculation of stature from the skeleton involves determining the length(s) of long bones, which are then used individually or in combinations in regression equations to determine living stature.
The anthropologist will be able to select the correct stature algorithm(s) only after determining sex and ancestry since the long bones have proportionally different relationships to overall stature in different sexes and populations. Since the estimated stature derives from long bone lengths that do not change significantly after maturity, this approach gives a range that does not take into consideration loss of stature from compression of the spinal fibrocartilages. A correction is usually applied for individuals whose age is estimated to be over thirty years.
Statures for children whose long bones have not completed longitudinal development are based upon the diaphyseal length. When long bones are incomplete because of trauma or taphonomic effects, it is sometimes possible to estimate the vital length of some bones by proportionality techniques.
The estimated lengths are then used in calculation of stature with the caveat that this approach introduces additional error in final calculated stature, thus widening the range estimate. In general, the best estimates of stature are based upon multiple bones, which are used in algorithms derived from population data reflecting current secular trends.
Anthropologists are sometimes asked to render estimates of the living weight of a decedent who has been reduced to bones. Putting aside ancillary information such as belts, shoes, and other clothing that may accompany remains, the answer will require strong qualification. Since an individual may lose as much as 50% of his or her body mass over a relatively short time (e.g., cachexia, starvation, etc.), such estimates are always questionable, and particularly so when the decedent appears to have been an indigent.
Accordingly, statements about frame size, proportionality, and the distribution of muscularity are preferable. Cross-sectional thickness or simply the weight of various bones in combination with proportionality ratios can provide information about how much soft tissue weight an individual might be expected to carry. This picture may be refined by a careful examination of entheses, the points of tendon insertion, which are modified by muscular activity over a period of time. Thus, one may arrive at an estimate of how well developed an individual may have been for a particular frame size and stature at some point in life. Examination of the pattern in which the skeleton has reinforced itself in response to habitual or repetitive biomechanical action has sometimes proved useful in the inclusion or exclusion of certain occupations, sports, or other activities performed over a period of several years, which may alter a list of suspected matches.
1.2.5 Individualization
Establishing the intersection set between sex, age, ancestry, and stature into which the decedent falls will eliminate a substantial number of suspected matches and false leads, and may help in redirecting the investigation into the identity of an unknown. An estimate of the postmortem interval (see below) will reduce the list further. When these data, combined with a list of unique identifiers, are compared to a database of missing persons, the list of possible matches usually reduces to a manageable few. At the discovery of unknown human remains, the authorities will either have a theory about the identity of the decedent or not. If there is a suspected match, all pertinent antemortem data will be assembled. This will include dental charts, bitewings and panographic images if available, old x-rays, or other medical images (e.g., CT scans, MRI, etc.). When images are unavailable, medical records describing prostheses, pacemakers, shunt devices, cosmetic implants, orthopedic devices, and the like may be sufficiently detailed for comparison to the postmortem evidence. Antemortem records of diseases that would be expected to leave evi-
dence in the hard tissues are also useful, particularly when the incidence of a disorder is known. Detailed descriptions of conditions (e.g., fractures, lesions, etc.), procedures, and appliances (including serial numbers) are useful. These antemortem data should confirm or exclude a potential match. In some cases of suspected identity, when none of the foregoing is available, it is sometimes useful to perform a skull-to-photograph superimposition. Although traditionally used to exclude matches, some have successfully employed video superimposition to achieve positive identifications when a complete skull and good quality photographs from several angles are available.
If open-mouth photographs are of sufficient resolution and detail, a direct comparison between the antemortem and postmortem anterior dentition may be possible. This approach rises to the standard of positive identification when combinations of features such as treatments (e.g., crowns, cosmetic modifications, extractions, etc.) and anatomy (e.g., diastemas, rotations, embrasures, etc.) provide multiple points of comparison. This technique is best deployed jointly by the anthropologist and the odontologist.
The identification process follows a Bayesian statistical model. The likeli hood of an individual being a particular sex, age, ancestry, and stature is roughly the product of the individual probabilities of being any one of those things. When individual identifiers are available, those with a known
incidence can be entered into the calculation, reducing the set of possible matches toward unity. Identifiers that can be traced directly to a decedent provide the basis for a positive identification, e.g., an intramedullary rod or a pacemaker with a serial number that matches a surgeon’s record for a particular patient. In such instances it is imperative that direct association between the decedent and the device can be established. For example, an orthodontic or orthopedic device affixed to the remains is preferable to one that has become detached. Experience in mass death incidents involving scattered and commingled remains bear this out. In some instances an implant, orthopedic device, or prosthesis may be found in a decedent without a suspected match. If the medical artifact bears a serial number and can be attributed to a particular manufacturer, it is sometimes possible to trace the device to a particular treatment facility, and thence through surgical records to a recipient. Whatever the means of identification, in the post-Daubert era, all conclusions and the techniques from which they are derived will require robust statistical support. As an example, though used as a basis for positive identification for years, comparison of ante- and postmortem frontal sinus x-rays has only recently been validated.
When unknown remains come to light for which there is no suspected match, the only remaining course of action is submission of the osteological and odontological findings to the appropriate database (see below).
1.2.6 Postmortem Interval
Forensic anthropologists are sometimes asked to estimate the postmortem interval (time since death) for a set of remains. The main reasons for estimating the postmortem interval are the inclusion or exclusion of suspects, reduction of the number of possible matches in a database, and determination of the forensic significance of a set of remains, i.e., is the decedent an archaeological or historical specimen, or a contemporary case that requires investigation? On most occasions, when an anthropologist is asked to determine the postmortem interval, the decedent will have been dead for weeks to years. Ideally, the remains will be pristine, and it is for this reason that many examiners prefer to attend the recovery, whether it may be an exhumation, collection of scattered bones, or even submerged remains. The anthropologist may supervise and document the process, collecting relevant samples, e.g., insects, botanical specimens, clothing, coins, or other “time givers,” which will be transmitted to appropriate specialists for further analysis. But, most importantly, he or she will want to assess the remains in context before any processing occurs. General observations will include corporal (from the body) as well as environmental information: What is the quantity and quality of the remains? Do the remains express any odor? To what extent are the remains scavenged and weathered? What are the characteristics of the local
weather, terrain, water sources, and fauna, all of which will influence the rate of decomposition or disassembly of remains? In addition to these two major sources of information, there are two general approaches to timing a death:
rate methods and concurrence methods. The degree to which bone has lost mineral and organic content, the change in sound or electrical conduction properties of bone, changes in specific gravity, and the amount of total lipid lost are examples of features that change with documentable rates. The details of these and other rate techniques are beyond the scope of this discussion, but may be found elsewhere. Concurrence estimates of the postmortem interval depend upon establishing an association between the remains and an object or event for which time can be fixed. An individual will not have died before the most recently minted coins in his pockets; there may be a scattering of leaves upon the body from nearby trees, which places its death before leaf fall, a natural event whose timing will be known to local botanists. The state or type of clothing may reveal season of death as well as time of day or night, etc.
When an elderly decomposing, mummified, or even skeletonized individual is discovered indoors, one often need look no further than the oldest letter in the mailbox. Good summaries of concurrence methods are available.
Whatever the approach taken, the time interval estimates must become broader as the actual postmortem interval lengthens. Because the estimate may be used to establish or exclude possible matches, or entered into a database along with other information, it is better to err on the side of more inclusive estimates than to exclude a true match through overconfidence.
Above all, it is important to avoid a mindset about what to expect. In 1999, while relocating some prison burials from ca. 1900, the author encountered an individual with nearly complete integument, copious adipocere, and a substantial amount of pink acellular skeletal muscle. Most of the other decedents were, as expected, represented by little more than dental fragments and coffin splinters. Just short of proclaiming the burial a much more recent one, he was reminded of an almost identical experience described by William Bass, who in the 1970s encountered similar findings in a Civil War era burial.
Important timing information will almost always be lost in the process of recovery, transport, processing, and storage of remains. When the anthropologist is asked to examine remains at the end of this process with little or no reliable information about context or procedure, it is prudent to
refrain from any except the most general estimate of postmortem interval.
1.2.7 Trauma
An important part of the anthropological analysis will be an assessment of traumatic injuries and other diseases or disorders sustained by the decedent.
While recognizing that there are far more causes of death that will not be reported by the hard tissues, those that do affect the skeleton or dentition represent the most enduring kind of evidence. Hard tissue injuries are designated as antemortem, perimortem, or postmortem according to time of occurrence.
1.2.7.1 Antemortem Trauma and Pathology
Antemortem injuries and diseases will often be of use as identifiers (see above). The classic examples are oral or orthopedic pathologies and their respective treatments, prostheses, etc. Certain chronic disorders, e.g., rickets , DISH (diffuse idiopathic skeletal hyperostosis; Belanger 2001, 258–267), advanced rheumatoid disease, etc., which exhibit skeletal facies, are also valuable in individualization when these have been noted in the medical history of a suspected match. Some chronic antemortem conditions may extend to the end of life, and on a few occasions, may even contribute to death. Obviously, such findings assume added importance when a clear cause of death cannot be shown. A skeleton with a pacemaker beneath the disarticulated bones of the thorax was recently encountered by the author. Subsequent tracking of the serial number identified an elderly decedent with a long history of cardiovascular disease. Though not as diagnostic as an atheromatous set of coronary arteries in the hands of a pathologist the day after death, the finding suggests, at least, a contributing cause. Although one occasionally finds old projectiles (bullets, shotgun pellets, etc.) embedded in the skeleton, most traumatic antemortem injuries will have been due to blunt force since one is more apt to survive these than blade or firearms assaults.
1.2.7.2 Perimortem Trauma
Perimortem injuries are those that occur at or near the time of death and are most likely to be associated with the true cause of death. Accordingly, such injuries become a critical focus. The most frequently encountered fatal perimortem defects are induced by gunshot, blade, or a blunt object forcibly applied. Each of these produces more or less characteristic defects. As a two-phase material (calcium hydroxyapatite and collagen), bone withstands compression and stretch. Under slow loading of force, the struck surface compresses while the opposite side stretches. Because bone is weaker under tensile forces, the stretched side fails first, often producing concentric cracking (as in the flat bones of the skull) or concoidal (wedge-shaped) fracture lines emanating from the point of failure. Under rapid loading (as in a bullet strike), the bone responds as a brittle material. In the latter instance one may see radiating cracks across the bone surface, or none at all.
Gunshot injury: The rules for interpretation of gunshot wounds (GSWs) in hard tissue differ somewhat from those in fleshed cadavers. In most instances, given an adequate sample of remains, one should be able to determine (1) entry and exit sites, (2) the approximate angle of entry of a projectile, (3) the order of entry defects if in the same surface, and (4) an approximation of caliber, or at least the elimination of certain calibers. Because the soft tissue has disappeared, and because garments may not be available for inspection, determining range of fire is often not possible. Except when a projectile has struck an intermediate target, the entry defect should provide, at least in one dimension, the approximate diameter (caliber) of the round.
Variations in the shape of an entry from circular to elliptical report the approximate angle of entry. The exit is generally distinguished by the presence of an outward bevel. Usually, the exit defect will be irregular and somewhat larger than the entry because of deformation of the round during its transit through the target. Both entry and exit bevels will have edges that slope approximately 45° from the incident angle. This feature owes to the manner in which fracture lines propagate through the hydroxyapatite crystal. Notable exceptions to this rule include the keyhole defect produced by a low-angle strike tangent to the skull. In this case, a furrow resembling a keyhole is produced.
Although the round may not enter the skull, a bevel is produced on both the outer and inner surfaces.
Double beveling may also be observed when the projectile strikes an intermediate target such as a glass pane, screen door, etc., causing the round to lose stability, thus imparting its energy into the target in an unpredictable manner.
Detailed descriptions of the interaction of projectiles and bone may be found in several sources (DiMaio 2003, 175–83). If garments accompany the remains, they should be examined for defects overlaying any ballistic injuries for possible indications of range of fire, such as soot or scorching. Ballistic metal usually transfers some of its substance to the bone through which it passes. Rounds entering the body and skull are often fragmented as they strike bone tissue. For this reason, remains believed to contain ballistic materials should be radiographed before an examination begins. This is especially important when GSW defects are present in the skull. Some small-caliber rounds often fail to exit the skull. When this is the case, following x-ray, the skull should be opened and examined to determine the path of the round and to retrieve it for ballistic examination.
Blade injury: When death appears to be the result of sharp force injury, a close examination of all bone surfaces is imperative. Imagine the torso from chin to the pubic bones (the vital area), then picture the subtending bones (vertebrae, sternum, ribs, clavicles, scapulae) painted upon this surface. When the torso is morphed into a round target, and the underlying bones into a bull’s-eye, the latter comprises about 65 to 75% of the target. The forensic implication is clear.
In theory, in a fatal blade injury one would expect bone to be marked in the majority of such cases. The extremities, especially the hands and forearms, and occasionally the legs, may bear defensive injuries as well. Therefore, all bones should be examined, to the extent possible, before cleaning and again afterward. Care must be taken when macerating remains not to remove or damage the periosteum.
Blade marks are often seen in this fibrous tissue sheath overlaying undamaged bone cortex. These injuries are best viewed in oblique light under low-power magnification, or under oblique fluorescence.
Defects may be captured for comparison before further cleaning by making a cast with polysiloxane or similar material. Unlike ballistic metal, blades rarely transfer any of their substance to bone. However, when a sharp edge is applied to a bone obliquely, microscopic examination will usually reveal a “bar code” effect, resulting from defects in the cutting edge as the blade is applied. The same is true when a serrated blade strikes bone at a low angle. These markings may be matched to a suspect blade using a comparison microscope. As is the case with soft tissue blade injuries, it is unlikely that the defects will yield information about the dimensions of the offending blade.
When the tip of a blade is forced into a bone, it is sometimes possible to determine whether it is backed or sharp on two edges (as in a dagger). Cases involving postmortem dismemberment will usually present several kinds of blade injuries, from knives, manual and power saws, cleavers, and even axes.
These must be distinguished from perimortem blade assault. Careful microscopic examination will usually differentiate knives from saw blades, and manual saws from circular and reciprocating saws. Further differentiation between various types of saw blades may also be made microscopically.
On a few occasions, the author has observed vital reaction in the periosteum adjacent to the site of dismemberment of an extremity.
This finding, far more common in soft tissue, indicates active circulation, though hopefully not consciousness, during the removal of the limb. When multiple blade injuries are present, some investigators will create a cut map, i.e., a three-dimensional representation of the skeleton and all of the injuries. This reporting format is useful in the context of possible witness accounts, and may help in differentiating fatal, nonfatal, and defensive injuries. Finally, in the case of remains outdoors, it is important to distinguish between blade injuries and pseudotrauma caused by animals with scissoid mouth parts, e.g., turtles and carrion birds, gnawing by scavengers with carnacil dentition, and trampling by animals.
Animal chewing will usually produce markings on opposite sides of a bone as the jaws occlude, whereas true blade marks will appear on only one surface. As in the case of all penetrating injuries, blade or ballistic, it is important to examine any garments associated with the remains for defects that may correspond to the injuries.
Blunt force injury: Blunt force injuries are the most common form of mechanical trauma. Caused by relatively slow loading rates, they allow bone to deform before failure, producing characteristic damage patterns. Because the energy (E) transferred to the bone is half the product of the mass (m) of the object striking it and the square of the velocity with which it is delivered (v2), velocity will make the greatest contribution to the damage observed. Keeping this relationship in mind, one can reduce the number of possible scenarios leading to a particular injury. A second important consideration is the area through which the energy is delivered. A blow of 75 ft.lbs.s–1 delivered by the flat side of a 12 × 2 inch plank will do less damage than the same amount of energy delivered by the 7 square inch face of a sledge hammer. The same is true of comparable energies delivered to curved vs. flat surfaces, e.g., when the hypothetical plank is slammed against the body wall vs. the curve of the parietal bone. Likewise, equal force applied to a healthy vs. diseased bone (tumor, osteoporosis, etc.) will often result in different degrees of damage. When examining unidentified skeletal remains, it is important to remember that some mechanical injuries may be incidental. These will usually appear as perimortem injuries, although they do not contribute to death. For example, severe skull or cervical fractures may have been caused by
falling down a staircase after a fatal coronary, or from a utility pole after a lethal electrical shock. The author once had the opportunity to examine skeletal material recovered from a collapsed area of a long abandoned historic mine. Though many of the bones were broken, it was impossible to know whether the two victims had expired from asphyxia, dehydration, or the crushing effects of the collapsing shaft.
It is important to consider that force applied to one part of the skeleton may be transferred, causing damage elsewhere. Shock from a hard landing may be transferred through the legs, damaging the bones of the pelvis or spine, and vertical loading of the spine from below has sometimes resulted in ring fractures of the skull base. A blow to the left gonial angle may cause a hinge fracture of the right mandibular ramus when the head is arrested against an unyielding surface, and the same principle applies in the classic contrecoup skull fracture. Reconstruction of a shattered skull, though time-consuming, may provide information about the number and order of strikes, or reveal a pattern that suggests the nature or class of weapon used.
In a recent case, the decedent’s skull was crushed by the right rear wheel of the vehicle from which she “fell.” Arrested later, other occupants of the car alleged that she “opened the door in an intoxicated state and fell beneath the wheel.” An alert pathologist observed that there was too little blood at the site where the tire rolled over the skull, and called for an anthropological examination. Reassembly of some eighty-five fragments revealed three suspicious patterned injuries that later proved to have been caused when the victim was struck repeatedly with a socket wrench. She had exsanguinated elsewhere before being dumped on the road. It is essential that all fragments be examined carefully for transferred evidence or for a more detailed toolmark analysis. Experienced examiners will recall instances of wood splinters, glass fragments, bits of paint, etc., embedded in bone later to be associated with a bat or a broken bottle with complementary bone chips, hair, or dried blood.
Occasionally, one encounters remains that bear blunt injury defects that appear to have been made by more than one kind of object. Such findings may indeed represent the work of more than one assailant, but most often will have been caused by repeated application of the same object at different striking angles, the classic example being crescent and round depressions on a skull from application of the edge and flat face, respectively, of the same hammer. Compound implements are of particular interest in this regard. The author once examined remains bearing several crescent depressions and one elongated full-thickness fracture on the skull, and a small rectangular punchout on the sternum. The implement, later associated with the assault, was a tire tool. The lug wrench end, applied at an angle, produced the crescent fractures while the handle had created the elongated depressed parietal break as well as a defensive fracture of the ulna. The nib, rectangular in cross section, was a perfect fit for the defect in the sternum. Other examples are provided by roofing hammers, ball peen hammers, single-bladed hatchets, etc., all of
which produce at least two kinds of patterned injuries, depending on which side is applied to the target. Where blunt force injuries are concerned, a three-dimensional imagination and an occasional stroll through the local hardware store are the examiner’s best analytical tools.
1.2.7.3 Postmortem Trauma
Postmortem trauma is an important category of damage in skeletal remains that must be distinguished from insults occurring near the time of death.
Although, strictly speaking, the “fall following a coronary” cited above qualifies as postmortem trauma, the phrase is most often used to describe modifications of remains that occur some time after death. Forensic anthropologists will recognize several categories of effects stemming from natural and anthropogenic causes. (1) In cases where remains are exposed, skeletal components may be damaged by movement due to natural forces. As bones disarticulate, they may be scattered by water or wind, depending on the slope of the terrain and the amount of water running across it. Fluvial transport often results in damage to ribs and the delicate structures of the skull base, depending on water velocity and distance traveled. As bones dry, some of the flat elements of the skeleton may warp and crack, producing damage that might be confused with injury. Similarly, buried remains subject to many cycles of wetting and drying may display breakage of ribs, spinous processes, and other effects. The weight of soil above a collapsed coffin may produce damage to the rib cage or pseudotrauma in the anterior dentition or delicate bones of the maxillofacial area. (2) The most common source of scattering and postmortem damage in exposed remains is animal activity. Large and small mammalian scavengers leave characteristic dental markings, usually perpendicular to the long axis of a bone. In some cases, bones will
be crushed by powerful jaws, e.g., bears, alligators, feral hogs. When recovering scattered remains, it is wise to ask what kinds of animals inhabit the area. Some familiarity with the dentition and the characteristic patterns of scavenging of animals within the area of search is useful.
It is important to remember that most scavengers will be attracted to wound sites, and that evidence of injury in bone, fatal or otherwise, may thus be altered, obscured, or eliminated altogether. (3) Anthropogenic damage is often the result of “discovery by bulldozer backhoe.” Operators of heavy equipment in rural areas often mangle remains in the act of discovering them, causing additional difficulty in distinguishing actual perimortem injury. One colleague wryly noted that “if one wants to find remains in a large field, one has only to instruct someone to ‘brush hog’ or till the area.” Colleagues in coastal regions often describe postmortem “propeller” damage inflicted on floating remains. The most problematic instances of anthropogenic damage are those that produce recovery and processing artifacts. A ground probe may produce what appears to be a bullet hole in shallow burial. Shovels and trowels in the hands of inexperienced investigators may induce what appear to be blade or chopping defects. Cases involving remains that have been intentionally disarticulated by knife, saw, etc., are often seen by a pathologist before the anthropologist is consulted. On these occasions the initial examiner must carefully note and describe any additional cuts that have been made with the autopsy saw for sampling or other purposes, lest these be confused with original marks made by the assailant. Although most anthropogenic artifacts are easily distinguished from perimortem damage, they often provide a skillful cross-examiner with opportunities to confuse a jury, and at the very least, may call into question the skills of those responsible for the recovery and analysis of the victim.
1.3 Databases
When the anthropological and dental analyses do not produce an identification, the biological profile, unique identifiers, and postmortem interval data are usually entered into a database. The most widely known U.S. database is the National Crime Information Center (NCIC), which includes descriptive information for analyzed unknown remains as well as missing individuals.
Many states operate databases and missing persons clearinghouses for their own jurisdictions. Still other databases specialize in a particular demographic segment of the national population, e.g., the National Center for Missing and Exploited Children (NCMEC).
In recent time, databases utilizing DNA technologies and powerful search engines have been created for a number of populations. These include the Armed Forces DNA Identification Laboratory (AFDIL) and the Combined DNA Index System (CODIS). The latter contains reference samples consisting of nuclear and mitochondrial markers from relatives of missing persons as well as mitochondrial and, usually, genomic markers from unidentified human remains. The CODIS system utilizes biological profile and dental information submitted with skeletal samples from unknown remains as metadata. When the system detects a possible hit, i.e., a match between a reference sample and a set of remains, it may be weak (i.e., achieve a less than desirable level of statistical certainty), owing to the badly degraded condition of the remains. Or, the system may find several possible matches either for the same reason or because the original reference samples were taken from individuals who were not first-degree relatives of the decedent. Given several possible matches, or one weak one, the anthropological and dental profiles are used to parse the list or to strengthen the weak match.
Presently, a number of problems reduce the effectiveness of databases.
Most do not interact with others because of incompatible formats, proprietary issues, or matters of confidentiality and access between jurisdictions and entities operating the various databases. The most important limitation on the use of any database in identifying unknowns, live or dead, is its inclusiveness. The best chance a missing individual or set of remains has of being identified resides in whether these have been submitted to a database with as much accompanying information as possible. Obviously, unidentified remains must have an accurate analysis. A significant problem arises because of the differing skill levels of those who initially develop the profile.
If the unknown remains are sufficiently complete and “fresh” to allow accurate determination of sex, age, ancestry, and stature visually, then a report from a pathologist may be sufficient for use as critical metadata. However, when remains are incomplete, fragmentary, degraded, etc., the biological profile should be completed by an experienced forensic anthropologist.
Errors in the assignment of ancestry or age, improper dental charting, or other misinformation entered into a database will likely result in false elimination of a correct identity match, i.e., “garbage in, garbage out.” Likewise, DNA reference samples should be from the closest possible relative of the missing individual. When bone or dental samples from unknown human remains are submitted to the CODIS database, these should be accompanied by biological profile information. Although it is not always possible to accurately determine all of the features of the profile, an effort must be made.
The “submission” issue is a large one. Reasons for the U.S. population’s rejection of national forms of identity databasing have deep roots in a variety of historical, cultural, political, psychological, and religious factors. Many countries require that some form of personal identifier be entered into a national database; e.g., in Korea persons are fingerprinted at the age of eighteen. Though many large organizations and governmental agencies require and store various forms of personal identification, whether biometric, fingerprints, DNA, or others, these have very limited access and do not interact. Thus, their value in large-scale searches for the missing and unknown remains is negligible. In this connection, an increasing number of states have enacted statutes requiring that remains not identified within a particular interval must be submitted to the National Missing Persons (CODIS) Database. The promise of databases will not be realized until the problems of accurate data entry and interconnectivity as well as broad public acceptance and participation are resolved.
1.4 The Future
Changes in training and technology in the United States and elsewhere have already produced a generation of forensic anthropologists who have moved beyond osteoarchaeology applied to identification, and increasingly toward an amalgam of bone biology and chemistry, molecular analysis, and ever more sophisticated software and instrumentation. Contemporary forensic anthropologists will be as comfortable interpreting x-ray fluorescence data, analyzing stable isotope ratios, and reading MRI scans as their predecessors were with calipers and flat plate radiographs. Several predictions seem worthwhile:
