Forensic Taphonomy and Human Identification

Forensic Taphonomy and Human Identification

Content Warning

This presentation contains images that may make some feel uncomfortable.

Aims

  • Introduce the concept of taphonomy.
  • Familiarize with the stages of decomposition.
  • Appreciate post-mortem changes in bone due to burial, mummification, and burning.
  • Recognize the differences between animal and human remains.
  • Understand how to calculate Minimum Number of Individuals (MNI).

Forensic Taphonomy

  • Definition: The study of death and decomposition in medicolegal contexts, focusing on what happens after inhumation, derived from the Greek term "τάφος νόμος" meaning "the laws of burial."
  • Focus: The processes that affect body decomposition and preservation over time.

Body Farms

  • Discusses studies involving animal vs human subjects to enhance understanding of decomposition.
  • Ethical considerations in forensic studies utilizing animal models.
  • Challenges in establishing statistical robustness and representativity in research on decomposition.

Decomposition

  • Definition: The process by which organic material is systematically broken down into simpler forms, commencing immediately following death in all biological organisms.
  • Observations: Both macroscopic and microscopic physical and biochemical changes occur.
  • Chemical Processes Involved:
    • Autolysis: Self-digestion where cells are destroyed through their own enzymes.
    • Putrefaction: Microbial deterioration of tissues caused by the proliferation of bacteria, primarily from the gut microbiome.

The Smell of Death

  • Involves a variety of chemical compounds produced during decay, contributing to its distinctive odors.
Odor-Causing Chemicals in Decomposition:
  • Cadaverine (pentane-1,5-diamine)
    • Smell: Foul, rotting flesh.
    • Associated with the distinctive odors of urine and semen.
  • Putrescine (butane-1,4-diamine)
    • Smell: Putrid flesh, garbage, contributing to bad breath.
  • Skatole (3-methylindole)
    • Smell: Strong faecal odor; can have a flowery smell at low concentrations.
  • Indole (indole)
    • Smell: Pungent, musty, stale; utilized in low concentrations in floral scents and perfumes.
Thanato Exhibition
  • A multisensory experience centered on a custom perfume (Thanatos) designed to evoke the scent of a decomposing body.
  • Collaborators included artist Eric Fong, perfumer Euan McCall, and forensic anthropologist Dr. Anna Williams.
  • Components: The exhibition includes the physical product, a sculpture-based interaction, a short film, and photographic evidence from staged crime scenes.
  • Reflects on processes occurring after death and advancements in forensic science.

Stages of Decomposition

Fresh Stage (24-72 hours)
  • Pallor Mortis: Initial color changes in the body.
  • Algor Mortis: Cooling of the body approximately at a rate of 1.5°F (0.8°C) per hour for the first 12 hours post-mortem.
  • Livor Mortis: Pooling of blood that occurs 30 minutes to 4 hours after death, leading to lividity (blue-purple color change).
  • Rigor Mortis: Muscle stiffening peaking at 12 hours lasting up to 4 days; adult blowflies visit (oviposition).
Bloat Stage (4-10 days)
  • Characteristics: Includes marbling, purging, skin slippage, and the accumulation of gases.
Active Decay (10-20 days)
  • Activities: Involves high levels of maggot activity and observable odour; strong decomposition where soft tissue liquefies and thorax collapses.
Advanced Decay (20-50 days)
  • Observations: Reduced insect activity, absence of maggots, most soft tissues removed, dried skin potentially mummifying.
Dry Remains (50+ days)
  • Characteristics: Presence of dry skin, bone, and cartilage; bones may bleach, and vegetation may regrow around the carcass.

Postmortem Interval (PMI)

  • Involves assessing soft tissue and skeletal modifications to estimate time since death.
  • Various factors like temperature and weather can adversely affect decomposition rates.
  • Estimation Methods: By calculating Accumulated Degree Days (ADD), which considers temperature variations affecting decomposition:
    • extADD=extsumoftheaveragedailytemperatures(in°C)ext{ADD} = ext{sum of the average daily temperatures (in °C)}
  • Total Body Scoring (TBS): Evaluates decomposition levels across body regions and is computed as follows:
    • extADD=10(0.002TBSimesTBS+1.81)ext±381.16ext{ADD} = 10(0.002TBS imes TBS + 1.81) ext{±} 381.16

Factors Affecting Decomposition

  1. Embalming
  2. Carnivore or rodent activity
  3. Soil pH
  4. Burial depth
  5. Body size/weight
  6. Temperature
  7. Insect access
  8. Trauma
  9. Humidity
  10. Rainfall
  11. Substrate and clothing present.

Excavation and Taphonomy

  • Understanding skeletal anatomy is crucial for excavating and analyzing human remains.
  • Proper interpretation of evidence aids human identification and recognition of disposal methods.

Preservation of Buried Bodies

  • Preservative Factors: Discuss various factors impacting preservation, including burial type, container presence, burial depth, clothing, soil acidity, and disturbance.
  • Case study of Tollund Man from 405 BC, recovered from a bog in Denmark.

Differential Preservation within Skeleton

  • Bone size affects the rate of diagenesis (alterations to the skeleton); bones with higher cortical content preserve better.

Quick Note About Decapitations & Dismemberment

  • Placement of skulls can vary, influencing preservation and identification challenges.

Mummification

  • Occurs in dry, cold, or high alkaline environments, often outside of archaeological contexts (e.g., lofts, wall cavities).

Saponification

  • Conversion to adipocere occurs in moist conditions, producing corpse wax observed in submerged bodies between 3 weeks and 2 months post-mortem.

Burned Remains

History of Examining Burned Remains
  1. 19th Century: Initiation of forensic investigations, notably in incidents such as mass disasters.
  2. 20th Century: Major advancements in methods across Europe; notable figures include Hummel, Schutkowski & Herrmann (1988), and ongoing work in the US involving McKinley, Thompson, Symes, Ubelaker, and Dirkmaat.
Thermal Effects on the Body
  • Exposure to heat alters tissue, commonly referred to as cremains or cremated remains, resulting in significant changes to bone structure and overall size.
Effects of Burning on Bones
  • Varying thickness of soft tissue influences heat exposure leading to differential alteration of skeletal remains. Accelerants may contribute to uneven burning and charring.
Differential Burning Classifications:
  1. Calcinated: Complete (hottest).
  2. Charred: Partial.
  3. Unburned Bone: Coolest.
Thermal Alteration to Bone Characteristics
  • Changes can include color alterations, shrinkage, fractures, affecting skeletal analyses. Observations include:
    • White to off-white coloration in bone due to indirect heat exposure.
    • Charred bone exhibits carbonization leading to blackened results.
    • Calcined bone, when organic matter is fully lost, results in grey to white hues.
Temperature and Bone Shrinkage Relation
  • Shrinkage is affected by temperature exposure over time, with lower percentages seen at temperatures up to 250 °C and significant changes at higher ranges around 700-1200 °C.
Modern Cremation Process
  • Typical cremation temperatures ranging between 800–1000 °C impact overall bone and soft tissue alteration significantly.
Identifying Burned Remains
  • Identification is challenging yet feasible through advanced techniques like strontium isotope analyses (87Sr/86Sr) aimed to assist in human identification amidst the lack of organic matter.

Human Identification Protocols

  • Key Questions:
    • Is it bone?
    • Is it human?
    • What bones are present?
    • What is the minimum number of individuals (MNI)?
    • Is it modern or archaeological?
    • What is the PMI?
    • What is the biological profile (sex, age, race, stature)?
    • Are there individual characteristics?
    • What was the manner of death?

Clyde Snow outlined a systematic process for the identification and recovery of remains, incorporated into forensic anthropology practices.

Summary

  • Forensic taphonomy examines postmortem processes affecting human remains preservation and recovery, aiding in the reconstruction surrounding death circumstances.
  • Influential environmental factors (temperature, humidity, pH) dictate the state of preservation observed in remains.
  • Understanding soft tissue decomposition is crucial, highlighting processes such as algor mortis, livor mortis, and rigor mortis among others.
  • The analysis of minimum number of individuals is vital in contexts involving multiple victims, aiding recovery and identification across various scenarios.

Lab Today

  • Activities: Assigning burning stages, evaluating burned bones to determine stages and temperatures of burning. Calculation exercises concerning minimum number of individuals (MNI) with practical engagement using mystery bone bags.

Thank you so much! You all have been a real treat to teach!