Forensic Anthropology: Methods, Roles and Death Investigation

• • Expert Testimony Standards: Evaluated under two landmark court cases:

    • Daubert v. Merrell Dow Pharmaceuticals, Inc. (1993): Replaced the Frye general acceptance test. Establishes the trial judge as the "gatekeeper" who must ensure all scientific expert testimony is both relevant and reliable to exclude "junk science".

    • Kumho Tire Co. v. Carmichael (1999): Extended the judge's gatekeeping obligation and Daubert's reliability requirements to all expert testimony, including technical and other specialized non-scientific knowledge.

Scope of the Discipline and Professional Roles

• Forensic Anthropology: A sub-field of biological/physical anthropology that applies the principles of skeletal biology and anthropological theory to a medico-legal context. It operates primarily at the individual level to identify human remains and analyze trauma.

• Forensic Archaeology: Focuses on the application of archaeological excavation, mapping, and scene processing techniques to properly uncover and recover human remains and associated evidence at a scene.

• Primary Employment Sectors: Practitioners are employed as university faculty/academics, museum curators, or as specialized personnel within medical examiner and coroner offices. The world's largest forensic anthropology laboratory is operated by the DPAA in Hawaii.

• Bioarchaeology vs. Forensic Anthropology: Bioarchaeology assesses human remains from prehistoric or historical archaeological contexts to interpret past population behaviors. Forensic anthropology addresses modern cases (typically under 50 years since death) tied to active law enforcement investigations.

• Scene and Case Responsibilities:

  • Law Enforcement: Controls and secures the physical scene.

  • Crime Scene Technicians: Document and collect physical evidence at the scene.

  • Medical Examiner / Coroner: Holds legal jurisdiction and control over the physical body.

  • Death Investigators: Deploy directly to scenes with law enforcement; responsible for investigating the medical state and context of the dead person.

  • Forensic Anthropologist: Acts strictly as a consultant to the medical examiner or coroner. FAs assist in scene recoveries, analyze skeletal trauma, provide estimates for the postmortem interval (PMI), and draft formal case reports detailing observations and calculations for the medicolegal authority.

Death Investigation Systems

• System in New Hampshire: NH operates a centralized, statewide Medical Examiner system, not a coroner system.

• NH Investigative Structure: Composed of 3 medical examiners, 1 chief forensic investigator, and a county-assigned network of Assistant Deputy Medical Examiners (ADMEs) who act as the on-scene death investigators. Forensic anthropologists serve as legal consultants to this state office.

• Coroner vs. Medical Examiner Systems:

  • Medical Examiners: Appointed medical doctors certified as forensic pathologists. They determine the cause and manner of death via medical records, microscopy, and surgical autopsy.

  • Coroners: Formed from the historical British "crowner" system to protect the Crown's tax interests. They are elected or appointed officials who do not need to be medical doctors. Responsibilities include legally determining death, identifying bodies, notifying next of kin, and signing death certificates. Counties choose coroner systems over MEs due to restricted financial resources, rural geography, or a lack of facilities.

• The Autopsy Process: From the Greek "to see for oneself". It is a thorough internal and external postmortem surgical examination of a body.

  • When Performed: Mandated for accidents, homicides, suicides, child deaths under 6, prison deaths, unattended deaths, or whenever foul play is suspected. MEs investigate roughly 20% of US deaths annually, performing autopsies on about 20% of those investigated cases.

  • When Exempted: Omitted at the discretion of the medicolegal authority if adequate clinical history accounts for the death and there is no suspicion of trauma or foul play.

  • Procedural Steps: External photos as received, photos unclothed/cleaned, documentation of marks/scars/trauma, toxicological/DNA sampling, surgical Y-incision and cranial opening to extract and weigh internal organs, fluid harvesting, body washing and cosmetic suturing. A final report typically requires 4 to 8 weeks to complete.

The Identification Hierarchy

• Sequential Case Analysis Checklist: Analysts must answer four consecutive questions when remains are processed:

  1. Is it bone?

  2. Is it human?

  3. Is it recent?

  4. Who is it? (Fulfilling the Biological Profile followed by Personal Identification)

1. Is It Bone?

• Mimics and Confounders: Dry wood, plastics, drywall, ceramics, and metals can mimic bone, especially when charred or fragmented by fire. For example, a metal hinge can mimic a human foot metatarsal bone.

• Testing Methods: Differentiated via bone microstructural analysis, pXRF (portable X-ray fluorescence) to check elemental signatures, or Alternative Light Sources (ALS) to evaluate natural bone fluorescence.

2. Is It Human?

• Locomotion and Functional Anatomy: Differences are driven by bipedal vs. quadrupedal locomotion and weight distribution (notably in pelvis and sacrum shape).

• Skeletal Maturity: Small, mature non-human bones display fully formed, fused joint structures, whereas human subadult bones of a similar size will feature unfused, distinct growth components.

• Microscopic (Histological) Features: Under a microscope, non-human bone cells organize into structured plexiform bone layers, while human bone is characterized by circular Haversian systems (secondary osteons).

3. Is It Recent? (Medicolegal Significance)

• Exclusions: Cases are non-significant if they represent historical archaeological context over 50 years old, ancestral grave goods, historic cemetery washouts, legal anatomical specimens, or military "trophy skulls".

• Taphonomic Clues: Fresh bone is heavy, greasy, holds a whitish-yellow color, and smells of decomposition; historic bone is lightweight, brittle, dry, fragile, and uniformly stained by surrounding matrix soil.

• Contextual and Biocultural Clues: Non-recent remains show extreme dental wear from grit, cranial modification, or trephination holes. Modern significance is proven by accompanying contemporary artifacts (driver's licenses), synthetic fabrics, or modern surgical intervention hardware like sternotomy wires, joint replacement parts, or ACL anchors.

• Bomb-Pulse Radiocarbon Dating: Measures levels of atmospheric \(^{14}C\) absorbed into organic tissues (teeth, hair) during mid-20th-century thermonuclear testing. Comparing these values against the recorded bomb-pulse curve provides a precise estimate of an individual's birth or death year.

Age Estimation

• The Biological Profile: Encompasses sex, age, ancestry, and stature. These parameters are always "estimated" or "assessed" rather than "determined" due to natural human phenotypic variation.

• The Trajectory Effect: The statistical error range of a biological age estimate expands drastically across the lifespan. Subadult estimates can narrow to a window of 6–8 months because they measure tightly scheduled growth and development. Adult estimates stretch across decades (25–83 years) because they score highly variable, lifestyle-dependent skeletal degeneration.

• Subadult Dental Development and Eruption: The single most accurate biological indicator of subadult age. Tooth mineralization begins around the 6th fetal week at the crown and finishes at the root apex. Unlike long bone growth, dental development continues uninterrupted by starvation or illness. Mixed dentition refers to the co-presence of juvenile deciduous teeth and permanent adult teeth. Teeth move into occlusion (the biting surface) until eruption concludes in early adulthood. Females regularly show advanced dental development timelines compared to males.

• Subadult Osteology: Long bone diaphysis lengths are measured to age neonatal and fetal remains, which is crucial for determining infant viability in court. Long bones grow longitudinally and appositionally. A growing long bone is divided into four zones: diaphysis (shaft), metaphysis, physis (epiphyseal growth plate), and epiphysis (ends). These segments fuse completely once growth ceases.

• Epiphyseal Union Timeline: Epiphyses across the skeleton fuse systematically between the ages of 10 and 25.

  • First to fuse: The joints of the elbow region.

  • Last to fuse: The sternal end of the clavicle.

• Adult Skeletal Degeneration Methods:

  • Pubic Symphysis (Suchey-Brooks Method): Scores the progressive breakdown of the symphyseal face where the two pelvic bones meet. Young adult faces show distinct horizontal ridges and billows (Phase 1, male mean 18.5). Middle-aged faces flatten out and develop a distinct border ridge or symphyseal "chin". Older adult faces present an eroded, highly porous rim that exhibits severe structural breakdown (Phase 6, male mean 61.2).

  • Sternal Rib Ends: Evaluates the pit depth, shape, and thinning borders of the rib cartilage articulation surface with the sternum.

  • Cranial Suture Closure: Tracks the fusing and eventual obliteration of skull vault lines, scored from open to complete obliteration.

  • Histomorphometry: Microscopic counting of secondary osteons (Haversian systems) in a sampled bone cross-section. Because bones continuously remodel over a lifetime, osteon counts increase with age and are inputted into regression formulas.

  • General Degenerative Pathology: Tracked by widespread osteoarthritis, osteophytic lipping (bone spurs) on the margins of vertebral bodies, eburnation (a polished, ivory-like joint surface caused by bone-on-bone friction following cartilage loss), and advanced dental attrition/wear.

Sex Estimation

• Sex vs. Gender: Sex is a biological classification rooted in chromosomes (genotype) and anatomical traits (phenotype). Gender is a fluid, non-universal social identity. Gender cannot be read from the skeleton. Transgender individuals generally retain the skeletal features of their biological sex unless altered by facial feminization surgeries or long-term hormone therapy. Conflating sex and gender can cause misidentifications that stall investigations (e.g., Sage Smith, Kenneth Glaze, Chimney Doe, Julie Doe).

• Subadult Constraint: Sex estimation cannot be performed on subadult skeletons; human sexual dimorphism only manifests anatomically after the hormonal surges of puberty.

• Sexual Dimorphism: Human males generally feature larger, more robust skeletons with prominent muscle attachment sites. Human females present smaller, more gracile skeletons with specific pelvic modifications to facilitate childbearing.

• Pelvic Sex Estimation: The most reliable region for adult sex estimation, yielding up to 95% accuracy.

  • Ventral Arc: A distinct bony ridge on the anterior pubis; present in females, absent in males.

  • Subpubic Concavity: The curve of the inferior pubic ramus; concave in females, straight/convex in males.

  • Ischiopubic Ramus: The broad bone section below the symphysis; features a sharp, narrow edge in females and a dull, wide surface in males.

  • Subpubic Angle: Forms a wide, open arch in females and a narrow, acute angle in males.

  • Greater Sciatic Notch: Evaluated on a scale from 1 (wide) to 5 (narrow). Females are wide ("rainbow" profile); males are constricted ("candy cane" profile).

• Cranial Sex Estimation: Yields 70–88% accuracy across 5 primary features:

  • Nuchal Crest: Smooth and flat (1) in females; presents a prominent, downward-hooked bony ridge (5) in males.

  • Mastoid Process: Small and short (1) in females; large, wide, and robust (5) in males.

  • Supraorbital Margin: Sharp, knife-like upper eye orbit rim (1) in females; thick, rounded, and blunt (5) in males.

  • Glabella: Smooth, flat frontal bone (1) in females; a projecting, thick supraorbital ridge (5) in males.

  • Mental Eminence: A narrow, pointed chin (1) in females; a broad, square, blocky chin (5) in males.

  • Walker (2008) Logistic Discriminant Functions: Mathematical formulas that apply specific statistical weights to cranial trait scores. A calculated score under 0 indicates a male; a score over 0 indicates a female.

• Long Bone Metric Analysis: Reaches 88–90% accuracy by measuring maximum joint diameters (e.g., head of the femur). A mathematically derived sectioning point splits the male and female sizing distributions, though an area of intermediate overlap exists.