Chapter 8: Identifying Human Skeletal Remains

WHO IS IT?

“Who is it?” is one of the first questions that law enforcement officers ask when they are faced with a set of skeletal remains. In order to answer this question, “who is it?”, forensic anthropologists construct a biological profile. A biological profile is an individual’s identifying characteristics, or biological information, which include the following: sex, age, stature, ancestry, skeletal variation, trauma, and pathology. ³ Each feature narrows the pool of possible “matches” considerably- sex alone cuts it by half. If a skeleton is absolute and unharmed, these aspects can be assessed with great correctness. Using the most recent systems, sex can be established with assurance, age estimated to within about 5 years, and stature approximated with a typical deviation of about 1.5″ (3.5 cm). However, forensic anthropologists are more likely to be dealing with incomplete, fragmented specimens so they must be equipped to glean as much information as probable from every bone. ⁵ Forensic anthropologists typically construct a biological profile to help positively identify a deceased person.³

Positive identification needs to be established for a number of reasons including inheritance, remarries, wills, insurance, homicide prosecution, and closure for relatives. A forensic anthropologists cannot establish the identity of a deceased person, as this is a matter of legality. Thus, only legal authorities, such as the sheriff, coroner, or medical examiner can establish identity by signing the death certificate.²

Identification Using Individualizing Characteristics

One of the most frequently requested analyses within the forensic anthropology laboratory is assistance with the identification of unidentified remains.³ Types of identification include tentative, circumstantial, presumptive and positive types.⁴ While all components of a biological profile can assist law enforcement officers and medical examiners to narrow down the list of potential identifications, a biological profile will not lead to a positive identification. The term positive identification refers to a scientifically validated method of identifying previously unidentified remains. Presumptive identifications, however, are not scientifically validated; rather, they are based on circumstances or scene context. For example, if a decedent is found in a locked home with no evidence of forced entry but the body is no longer visually identifiable, it may be presumed that the remains belong to the homeowner. Hence, a presumptive identification.³

The medicolegal system ultimately requires that a positive identification be made in such circumstances, and a presumptive identification is often a good way to narrow down the pool of possibilities. Biological profile information also assists with making a presumptive identification based on an individual’s phenotype in life (e.g., what they looked like). As an example, a forensic anthropologist may establish the following components of a biological profile: white male, between the ages of 35 and 50, approximately 5＇7＂ to 5＇11″. While this seems like a rather specific description of an individual, you can imagine that this description fits dozens, if not hundreds, of people in an urban area.³

This data can be compared to local or national missing persons databases. One such national database is the National Missing and Unidentified Persons System or Namus.gov. Namus is a free database that anyone can search, but missing person’s data can only be added by coroners, medical examiners, and some anthropologists. Another national database is the National Crime Information Center, however this database can only be used by authorized personal, such as law enforcement.² Therefore, law enforcement can use the biological profile information to narrow their pool of possible identifications to include only white males who fit the age and height outlined above. Once a possible match is found, the decedent can be identified using a method of positive identification.³

Positive identification represents a much higher level of probability and involves a two-step process. First, anatomical features must be discovered that are shared between the examined evidence and the known antemortem information relating to a particular individual. Second, the analyst must determine that the features being compared are sufficiently unique to enable the identification. In addition, any differences must be noted and explained in a satisfactory manner. When errors are made in identification they usually fall into two categories: (1) differences are considered as evidence for exclusion that actually represent other factors, and (2) shared features are presented in support of identification with insufficient consideration of their uniqueness. Great caution is needed in interpretation since misidentification can lead to tragic consequences.⁴

Contributions of forensic anthropologists to identification are especially needed and valuable in the analysis of extensively decomposed and/or skeletonized human remains. Experimental research indicates that the process of decomposition can rapidly destroy many indicators commonly used in identification, although the rate of destruction depends on many variables. Research indicates fingerprints survive 4 days postmortem with warm temperatures but more than 50 days with cold temperatures.⁴ Because of this identification with fingerprints can only be conducted on remains that are in the early stages of decomposition.²  Postmortem iris recognition ranged from 2 to 34 days, depending on the variables involved. Of course, this research is location specific, and rates may vary in other regions.⁴

Positive identifications are based on what we refer to as individualizing traits or characteristics, which are traits that are unique at the individual level. For example, brown hair is not an individualizing trait as brown is the most common hair color in the U.S. But, a specific pattern of dental restorations or surgical implants can be individualizing, because it is unlikely that you will have an exact match on either of these traits when comparing two individuals.³

A number of positive methods are available to forensic anthropologists, and for the remainder of this section we will discuss those methods.³

Visual Comparison

Another type of identification that forensic anthropologists are not involved in are visual comparisons. This method involves bringing in friends or relatives of the presumed decedent to view the body and determine if these remains belong to their loved one. However, this method can only be conducted on remains that are in the early stages of decomposition.² Research and casework has also demonstrated that facial recognition is generally unreliable in identification, especially with advanced decomposition.⁴

Fingerprints

Fingerprints have been accepted as being individually unique to each person. The courts frequently accept positive fingerprint matches conducted by an expert witness, as proof of identity beyond a reasonable doubt.⁶

Prior to the modern advent of DNA analysis and biometric scanning technologies for positive identification, fingerprints and dental record x-rays were the only truly positive means of making a conclusive identification.⁶

Fingerprints are unique patterns of lines and ridges that exist on the areas of our hands and fingertips, known as the plantar surfaces. These unique patterns have been classified in categories and features since the late 1800’s. The various categories and features allow each digit of a person’s fingers to be catalogued in a searchable system or database. These unique categories and features do not change throughout a person’s life, unless they are subjected to damage through physical injury or intentional abrasion. The impressions of our fingerprints are often left on items we touch because the oils our bodies produce act like an invisible ink adhering to smooth surfaces we touch, thus transferring these fingerprint impressions to those surfaces. These virtually invisible image transfers are commonly called latent fingerprints, and they are easily made visible on most surfaces through the application of colored fingerprinting powder that adheres to the oils left by our fingers. The powder sticking to the oil reveals the image of lines and ridges that make up the fingerprint.⁶

The unique lines and ridges of an unknown fingerprint can be searched in a database of known criminal fingerprints for identification. Today, this type of search is done electronically using a biometric scanning process known as Automated Fingerprint Identification System (AFIS). For smaller partial prints, identification of a fingerprint requires sorting through possible matches and conducting specific searches of print characteristics to make a match. If the person who left the print does not have a criminal record or their fingerprints are not on file, the only way a comparison can be made is to obtain a set of fingerprint impressions from that person. When this is done, the print examination will be conducted by a trained fingerprint expert who will search the print to establish as many points of comparison between the unknown print and the known-print as possible.⁶ Forensic anthropologists are generally not involved in this type of identification.²

DNA

DNA, or deoxyribonucleic acid, is a molecule that holds the genetic blueprint used in the development, functioning, and reproduction of all living organisms. As such, it carries the unique genetic information and hereditary characteristics of the cells from which living organism are formed. Except for identical twins, the DNA profile of each living organism is unique and distinct from other organisms of the same species. There are some rare cases where one person may carry two distinct types of DNA, known as Chimera where paternal twin embryo merge during gestation, or in cases where a bone marrow transplant enables the production of the marrow donor DNA in the recipient’s blood. In these rare cases, a person may test for two distinct DNA profiles for different parts of their body.⁶

In human beings, DNA comparison can enable high probability matches to be made between bodily substances and the person from whom those substances originated. Bodily substances containing cellular material, such as blood, semen, seminal fluid, saliva, skin, bone, and even hair root tissue can often be compared and matched back to its original owner with high statistical probabilities of comparison.⁶

Even very small amounts of material can yield enough material for DNA comparison. Importantly, DNA data-banks of known criminals and unsolved crimes are now becoming well established in North America. When a person is convicted of certain criminal offences, DNA is collected and submitted to these databases.⁶ 

Determining identification with the help of DNA has played an important role in this field of analysis.⁵ A tooth or bone sample needs to be collected and processed to collect the DNA. However, DNA tests are costly as well as destructive, so this is not a preferred way to identify skeletal remains.⁵

Radiographs

Comparative medical and dental radiography is used to find consistency of traits when comparing antemortem records (medical and dental records taken during life) with images taken postmortem (after death). Comparative medical radiography focuses primarily on features associated with the skeletal system, including trabecular pattern (internal structure of bone that is honeycomb in appearance), bone shape or cortical density (compact outer layer of bone), and evidence of past trauma or skeletal pathology.³ Techniques of positioning, magnification, beam centering, angulation and bone orientation must be matched between antemortem and postmortem radiographs to facilitate these comparisons. ⁴ One issue with using radiographic comparisons of bone for identification is that throughout a person’s life their bone is being remodeled, which could create discrepancies.²

Comparative dental radiography focuses on the number, shape, location, and orientation of dentition and dental restorations in antemortem and postmortem images. While there is not a minimum number of matching traits that need to be identified for an identification to be made, the antemortem and postmortem records should have enough skeletal or dental consistencies to conclude that the records did in fact come from the same individual. Consideration should also be given to population-level frequencies of specific skeletal and dental traits. If a trait is particularly common within a given population, it may not be a good trait to utilize for positive identification.³ 

Forensic odontologists are uniquely qualified to interpret dental restorations and other features related to the practice of dentistry. However, anthropologists share with odontologists an interest and expertise in aspects of dental morphology that can provide evidence for positive scientific identification.⁴

Unique Cranial Evidence

While other methods have led to tentative identifications, distinctive features present on the skeleton allow for a more certain classification. The skull frequently has provided the unique information needed for positive scientific identification in anthropological analysis for two primary reasons: (1) historically, considerable research has focused on the skull revealing great variation of many anatomical features, and (2) antemortem radiographs and related imagery frequently are available for the head and may include multiple views. Skull images can present numerous unique features useful for identification. Positive scientific identification can be accomplished by computerized tomographic (CT) examination of the frontal sinus, sphenoid sinus, ethmoidal mastoid air cells, as well as, aspects of the internal occipital protuberance, the mastoid processes, and cranial suture patterns including the location, length and slope of sutural lines.⁴

Frontal Sinus Variation

Although many features of the human skull display extensive variation and thus are useful for individual identification, many investigators have focused on the frontal sinus. This sinus located superior to nasion in the area of the supraorbital ridges displays remarkable variation ranging from minimal presence to large labyrinthine formations. Apparently reflecting environmental and developmental influences, even identical twins display morphological differences in frontal sinus expression.⁴

Although most early comparative studies of frontal sinus morphology utilized in medicolegal applications featured pattern recognition, metric and more sophisticated statistical treatments have been introduced as well. Scientists have introduced a metric approach that documented the vertical and horizontal dimensions of the sinus expression. They declared a match if the comparative measurements were within 5 mm of each other.⁴

Surgical Implants

Surgical implants or devices can also be used for identification purposes (Figure 8.2). These implements are sometimes recovered with human remains. One of the ways forensic anthropologists can use surgical implants to assist in decedent identification is by providing a thorough analysis of the implant and noting any identifying information such as serial numbers, manufacturer symbols, and so forth. This information can then sometimes be tracked directly to the manufacturer or the place of surgical intervention, which may be used to identify unknown remains.³

Facial Reconstruction

The technique of reconstructing a person’s face from their skeletal remains using a combination of art, anthropology, osteology, and anatomy is known as forensic facial reconstruction (or forensic facial approximation). It is without a doubt the most arbitrary—as well as one of the most contentious—methodologies in the discipline of forensic anthropology. Despite this criticism, facial reconstruction has been successful enough times to warrant continued research and methodological advancements. Facial reconstructions are made for remains thought to have historical value, as well as for remains of ancient humans and hominids, in addition to those implicated in criminal investigations.¹

Legal Admissibility

No two reconstructions for the same set of skeletal remains produced by different forensic artists are ever identical, and the data used to build the approximations is largely lacking. As a result, forensic facial reconstruction is not regarded as a method of positive identification recognized by the law, and is not admissible in court. Reconstructions are currently only created to support the process of positive identification in tandem with verified method.¹

Types of Reconstructions

Two-dimensional reconstructions: Antemortem images, the skull, and two-dimensional facial reconstructions are the foundations for these. Sometimes radiographs of the skull are used however, this is not ideal because many cranial features are not visible or are not scaled appropriately. Typically, a forensic anthropologist and an artist must work together on this technique. Karen T. Taylor of Austin, Texas developed a widely utilized technique for 2D facial reconstruction in the 1980s. Taylor’s technique is imaging an unidentified skull after attaching tissue depth markers at numerous anthropological sites. Drawings of faces on transparent vellum are then built upon life-size or one-to-one frontal and lateral photographic reproductions. The computer software applications F.A.C.E. and C.A.R.E.S. swiftly create two-dimensional facial approximations that are relatively simple to edit and manipulate. Despite the fact that they might produce more generic images than hand-drawn art, these programs may help speed up the reconstruction process and enable the application of tiny adjustments to the drawing.¹

Three-dimensional reconstructions: Modeling clay and other materials are used to build sculptures (formed from castings of cranial remains) for three-dimensional facial reconstructions, or high-resolution, three-dimensional computer graphics. Similar to two-dimensional reconstructions, forensic anthropologists and artists are typically needed for three-dimensional reconstructions. Computer programs manipulate stock photos of face traits, scanned images of the unidentified skull bones, and other available reconstructions to produce three-dimensional reconstructions. Due to the fact that they don’t come off as very fake, these computer approximations are typically the most successful in identifying victims. The National Center for Missing & Exploited Children adopted this technique and frequently uses it when releasing images of unidentified decedents to the public in an effort to identify the person in question.¹

Methods of Reconstruction

Over the years since its discovery, several variations of craniofacial reconstruction have been applied in numerous fields. As previously mentioned, it is a method that is commonly utilized today all over the world and has shown to help with forensic investigations by identifying victims of various crimes. To reconstruct the victim’s identity, forensic professionals will draw on their in-depth understanding of the facial muscles and tissue attachments on the skull. In order to accomplish so, it is crucial to take into account the skull’s appearance, the soft tissues that are related to it, and the corresponding scans (X-Ray, CT Scans, and ultrasound).¹

The Russian Method is a craniofacial rebuilding technique that makes use of the skull’s muscles. This technique emphasizes where the muscles attach to the skull and recreates the victim’s skull’s musculature using a material that resembles clay. The American Method is a different reconstruction technique that focuses on the skull’s surrounding tissue. This technique requires the facial tissue depth information captured using tissue puncture markers and/or ultrasounds on previous remains or living patients. Based on characteristics like ethnicity, sex, and age, this technique can show how different reconstructions of remains differ from one another. The American Method and the Russian Method are combined to create the Manchester Method. It is discovered to be the approach that is currently employed the most frequently. It performs the reconstruction using the skull’s musculature as well as tissue depth markers and landmarks.¹

Techniques of facial approximation are improving with enhanced information regarding the relationship of facial hard and soft tissues and more sophisticated computer technology. Despite these advancements, facial approximation does not represent a method of positive scientific identification. However, the generated image may prove useful to assist public communication that the remains of someone with particular visual and demographic characteristics have been recovered.⁴

Craniofacial Superimposition

Craniofacial superimposition compares features of a recovered skull thought to be of medicolegal interest with antemortem photographs of a missing person who might be represented by the remains. This technique may be employed when positive identification has not been accomplished through molecular analysis, dental reconstruction comparison or anthropological radiographic assessment. Usually, the method is utilized when complete skulls or crania are available for comparison, but attempts have been made using even fragmentary evidence. Once clear images are found that can be used to compare the recovered crania, forensic anthropologists must take the time to orient the skull, often using Q-tips as place markers, in order to be able to lay the images properly over each other. The techniques of comparison have become more complex and sophisticated but primarily allow exclusion rather than positive scientific identification. Images are often pulled from police records, surveillance or directly from relatives of the possible individual. The quality of this image typically corresponds to the accuracy of the exclusion process. ⁴ Because investigators must already be familiar with the identity of the skeletal remains, they are working with, this technique is not always used.¹ Photographic superimposition can lead to misidentification if not properly employed. Because of that this technique should not be used as the only means of identification.⁴

Applications to the Living

Although contributions of forensic anthropologists to positive scientific identification usually involve recovered skeletal remains, similar techniques can be applied to medicolegal issues involving the living. One such case should how radiographic evaluations of skeletal details were used to address cases of workers’ compensation fraud. Individuals in Colorado with pre-existing medical conditions were feigning injuries while at work and claiming workers’ compensation. Using different identities, they were making multiple claims for the same apparent medical condition. Comparative examination of radiographs revealed that multiple claims supposedly of different persons actually related to one person.⁴

Team Approach

Although anthropologists frequently apply their skills to individual skeletal features, ultimately identification represents a team effort. Apart from investigative efforts, reports and analyses by forensic anthropologists join those generated from analysis of DNA, fingerprints, dental restorations and other data. Ideally, identification should represent a holistic, comprehensive process that builds on the biological profile and circumstantial evidence.⁴

Future Advances

Critical evaluation of past progress reveals trends likely to produce future advances. Technological advances clearly represent key potential for enhanced capability in positive scientific identification. The images generated by computerized tomography (CT) reveal much more skeletal detail than those previously available from conventional radiography. The rapidly advancing technology available for imagery clearly will contribute to major advances.⁴

Recent years have witnessed increased scrutiny of the forensic sciences in the legal arena. Constructive criticism has stimulated research focus on probability assessment, cognitive bias, error analysis and the general scientific foundation of forensic applications. Future analyses of features contributing to positive scientific identification must relate accurately the probabilities involved. Those involved in the identification process must guard against cognitive bias that might impact assessment. Research must attempt to define the uniqueness of features commonly involved in skeletal identifications. Concepts of “match” and “consistency” likely will be replaced with more precise statements of probability and associated error. More sophisticated statistical analyses predictably will become apparent in the research designs targeting methods of identification.

The team approach discussed above likely will become more commonplace in the identification procedure. Individual techniques and statistical analysis present individual probabilities of identification. The team approach offers the potential for combined probabilities that should enhance the identification effort.⁴

Identification benefits from the training and experience of anthropologists conducting the analysis. Internationally, the best and brightest students are becoming increasingly attracted to the field of forensic anthropology. This surge of academic interest and dedication bodes well for the future of forensic anthropology and for methodology of positive scientific identification.⁴

 

References:

1. Aditya Singh, “An Overview of Forensic Facial Reconstruction,” Journal of Forensic Research 13 (2022). https://www.hilarispublisher.com/open-access/an-overview-of-forensic-facial-reconstruction-91421.html.

2. Angi M. Christensen, Nicholas V. Passalacqua, and Eric J. Bartelink, Forensic Anthropology: Current Methods and Practice, 2nd ed. (London: Academic Press, 2019): 443-451.

3. Ashley Kendell, Alex Perrone, and Colleen Milligan, “Bioarcheology and Forensic Anthropology” In Explorations, ed. Beth Shook, Katie Nelson, Kelsie Aguilera and Lara Braff (Arlington: American Anthropological Association, 2019). https://pressbooksdev.oer.hawaii.edu/explorationsbioanth/chapter/osteology/.

4. Douglas H. Ubelaker, Austin Shamlou, and Amanda Kunkle, “Contributions of Forensic Anthropology to Positive Scientific Identification: A Critical Review,” Forensic Sciences Research 4 (2019): 45–50. https://academic.oup.com/fsr/article/4/1/45/6794580.

5. Purva Wagisha Upadhyay and Amarnath Mishra, “Forensic Anthropology” in Biological Anthropology – Applications and Case Studies, ed. Alessio Vovlas (London: IntechOpen, 2021). https://www.intechopen.com/chapters/73372.

6. Rod Gehl and Darryl Plecas, Introduction to Criminal Investigation: Processes, Practices and Thinking (New Westminster, BC: Justice Institute of British Columbia, 2017). Download this book for free at https://pressbooks.bccampus.ca/criminalinvestigation/ as follows: digital format: on every electronic page print format: on at least one page near the front of the book.

Figure Attributions:

Figure 8.1 Tib fib growth plates by Gilo1969 at English Wikipedia is used under a CC BY 3.0 License.

Figure 8.2 Filling by Kauzio has been designated to the public domain (CC0).