Forensic Archaeology

Long lived isotopes

• Carbon dating can be useful for up to 50,000 years.

• Thorium-230 measurements can be used up to 400,000 years. Th-230 is a product of Uranium-238 decay.

Detection of Radiation + AMS

• Ionisation (Geiger) counter

• Scintillator detector:

  • Effective as measuring gamma radiation

  • Scintillator material emits light that is collected in photomultiplier tubes

• Accelerator Mass Spectrometry:

  • Most advanced way of measuring carbon-14

• AMS vs Radiation counters:

  • AMS counts number of atoms in sample, while scintillation counters measure infrequent radioactive decay events in sample

Sedimentation Rates + calculation

• Uranium is soluble and unreactive in sea water.

• Thorium is reactive and is removed eventually, falls into sediment

• Measurement of activity in sediment allows dating of process if sedimentation has been constant time.

• Idealised sedimentation rate of 2cm/1000 year.

To calculate sedimentation rate, e.g., of Th per 1000 years, with a slope of 0.003.

• Amount of sediment = ln(2)/slope of graph (0.003) = 231cm

• Then, half life of element, e.g., Th/1000 (how many years it’s stating) = 7.5 × 10^4 /1000 = 75

• Divide amount of sediment by years per cm to find rate in cm/year

  = 231/75 = 3.1cm per year

Unpaired electrons dating methods + paleodose definition + deriving it

Electron Spin Resonance (ESR):

• Repeatable dating method that measures amount of unpaired electron in artefact that have been created over time by ionising radiation.

Thermoluminescence (TL):

• Non repeatable dating method that depends on presence of unpaired electron in artefact that have been created over time by ionising radiation.

Artefacts must be electrical insulators, so cannot date metals!

Paleodose = dose of natural radiation accumulated by an archaeological sample.

Age = paleodose/annual dose

• To derive a paleodose, consider all data points, except ones which are too high, as possibly saturated.

What population of unpaired electron is max number + ESR and TL dating uses in various samples

• After about 1 million years, population of unpaired electron is maximum. All available electron trapping sites are occupied ~ saturation.

Bones, teeth, shells:

• Formed by living creatures, biomineralisation.

• Formed with a zero concentration of unpaired electron.

• We can date since their formation.

Carbon deposits:

• Caves, stalactites, stalagmites

• Formed with a zero concentration of unpaired electron

Flints:

• Older, geological material

• Formed with a zero concentration of unpaired electron, but all trapping sites for unpaired electron are long saturated, so cannot date flints from time of formation.

• If flint is heated, it discharges unpaired electron, resets clock to 0, then unpaired electron starts to build up again, so can date since flint heated.

Pottery/artefacts:

• Clay contains mineral crystallites, initially saturated.

• Can date time since pottery produced.

• Cannot for metals, as are conductors, electrons cannot be trapped.

Electron Spin Resonance (ESR) dating method

• Sample placed in a magnetic field, unpaired electrons have different energies, depending on spins ‘up’ or ‘down’.

• Sample absorbs electromagnetic radiation, in microwave region of spectrum, to flip spins of unpaired electron from low energy to high energy state.

• ESR spectrum provides absorption peak and its total area provides the quantitative intensity that can be used for dating.

• Calibrate intensity by a known standard or ‘additive irradiation method’.

• Intensity of ESR spectrum (in absorption spectrum, area under peak), measures concentration of unpaired electrons.

• Non destructive, repeatable method, as no discharge of the electron.

Defects in crystals + F centre

• Crystals are not perfect, type of defects:

• F centres are defects created when an anion vacancy is filled by an unpaired electron. These defects can trap unpaired electrons, affecting the optical and electronic properties of the crystals and are significant in dating methods.

Units of radiation

Rad = Radiation Absorbed Dose

= transfer of energy to matter, where 1 Rad = 0.01 Joules absorbed in 1kg of material.

Gray (Gy) = 1 Joule per kilogram

1 Gy = 100 Rad

Thermoluminescence (TL) dating method

• Detecting trapped electrons useful down to a few 100 years.

• Heating sample discharges trapped electrons by providing activation energy to escape their metastable trap sites by recombination with ions. As discharging occurs ~ non repeatable.

• Energy stored in solid is released as light when heated, which is captured and measured to determine the last time the sample was heated.

• TL detectors measures intensity of light, which provides concentration of unpaired electrons.

Learning from thermoluminescence (TL)

Biodosimetry:

• Measure radiation dose accurately using TL, e.g., radiotherapy patients. Use artificial phosphors that are sensitive to radiation.

Food irradiation:

• Used to prolong shelf life, reducing health hazard, bacteria.

• ESR and TL used to measure irradiated food samples, ensuring quality and suitability.

X Ray fluorescence + principles

• Non destructive, differentiates between oxidation states, enhanced by use of synchrotron light.

• Sample bombarded with high energy X rays, ‘knock’ electrons out of atoms.

• Knocked out electrons provide ‘holes’ in inner electron shells of atoms.

• Outer electrons drop into holes, emission of a photon in X ray regime.

• X rays will be characteristic of element, and their intensity will be proportional to concentration of element.

Fluorescent X rays characteristic:

• Mosely’s Law states that energy of a transition depends on (Z-1)² , where Z = charge on nucleus.

Conservation of water logged wood

• Wood when dry collapses + falls apart.

• ‘Holes’ have to filled in, by polyethylene glycol (PEG) ~ waxy, cheap, solid, water soluble.

  • Holes filled, slowly dried.

• Problem - as sulfur deposits found on ships in wood, when exposed to air, forms sulfuric acid, erodes material.

Duties and Responsibilities of a Forensic Anthropologist

• Assess whether an item, element or fragment of tissue is human

• Identify human remains - what is present, and/or missing

• No. of individuals

• Assess + record traumatic injuries

• Reconstruct fragmented bone(s)

• Assist with Disaster Victim Identification (DVI)

• Writing statements and reports, attending court to provide evidence

• Know when to utilise the help of specialists, e.g., radiologists.

Ethics of anthropology cases

• Political + social aspects of case

• Beliefs of victim’s families

• Danger to investigator

• Distress to survivors

Four fields of anthropology

• Physical/Biological anthropology

• Cultural anthropology

• Linguistic anthropology

• Archaeology

Exhumation vs Excavation

Exhumation = retrieval of remains whether archaeological techniques used or not.

Excavation = retrieval of remains + reconstruction of human activity at site and beyond.

Harris Matrix

• Tool used to depict temporal succession of archaeological contexts.

• Sequence of depositions and surfaces on a dry land archaeological site, otherwise called a ‘stratigraphic sequence’.

• Matrix reflects relative position and context of surroundings.

Advantages of investigators working with a forensic anthropologist

• Using a systematic + controlled approach.

• Understanding site formation process.

• Recognising post burial site disturbances + identifying cause.

• Effectively reconstructing events surrounding.

• Increased accuracy in collecting remains + associated evidence during recovery.

Four stages of implementing archaeological recovery methods for forensics

1.) Location - searching for remains above and below ground.

2.) Mapping - grid site ensuring detailed documentation of recovery.

3.) Excavation (where appropriate)

4.) Collection - appropriate packaging of remains for further lab analysis.

Locating remains (visual/foot searches)

Spiral:

• Works best for small teams, hillside locations

• Ensures no trampling of evidence

Strip/line:

• Common, most coverage if successful

Grid:

• Time consuming, variation of line search

• Multi-directional + multi-angled search

Quadrant/zone:

• Detailed searches of smaller areas

• Often implemented after remains found

Types of searches + search options

Search types:

• Open - scanning search, no excavation required.

• Obstructed - excavation required to locate remains etc.

• Submerged - underwater search

Search options:

• Aerial (planes, drones), walking grids, remote setting

Indicators of surface + buried remains

• Skeletal, remains, and/or body tissue

• Clothing, personal objects, weapons

• Decomposition, odour, staining,

• Insect activity

• Animal activity, scavenging

• Materials for body wrapping

Probes + shovels

Used within a defined grid area

Three types:

• T-bar

• Penetrometer (qualitative changes in soil compactness)

• Soil coring (check for mixing of soil horizons)

Mapping recovery site

• Set up datum point on a permanent structure, GPS coordinates of point.

• Set up grid over area of remains 3-4 metres square, four wooden posts connected with string.

• Tape measure from height of string to document location of each artefact or biological item.

• Detailed photography.

Excavation + recovery for surface remains and buried remains

Surface remains:

• Examine + record recovery area.

• Establish spatial controls + record primary and secondary surface deposits.

• Expose remains, collect evidence, and document context.

Buried remains:

• Identify + record burial outline.

• Excavate + record burial feature.

• Working from corner and across grid, remove soil in 5cm layers using hand trowel and brushes.

• Screen all soil removed.

• Only remove elements once mapped and photographed.

• Record + evaluate floor of burial feature.

Dealing with outline of grave when found

• Section grave

  • Adds depth to constraints of excavation.

  • Allows lateral access to grave + body.

• Preserve integrity of grave

  • Area of disturbance must be maintained throughout excavation.

  • Determine parameters of grave.

• Emptying grave fill

  • Recording each layer and pieces of evidence.

Key aspects of recording grave + contents

• Relationship of layers

• Soil descriptions

• Listing seized exhibits per context

• Archaeologists interpretation of each layer

Collecting evidence

• Drug fold (folding pattern used to secure items) for small items.

• Paper bags for bone, clothing and biological material, (as not plastic, as bones sweat, so not air tight bags!)

• Paper bags, then plastic bags, for bloody, semen remains.

• Infested material - sealed plastic bags - freeze in lab to kill insects.

Biological age vs Chronological age

Biological age = how old someone looks

Chronological age = how many years someone has actually been alive for

Age Estimation dealing with juvenile bones

• Less likely to survive burial environment, compared to adult bones:

  • As lower bone mineral content, susceptible to decay.

  • Graves of children are smaller, shallower, less well marked in soil, less chance of detection.

• Inexperienced excavators, who may not recognise bones as children remains, thus disregarded.

Ageing + structure in subadults

= length, fusion, dentition

1.) Linear increase in bone dimension

2.) Ossification of epiphyses

3.) Growth and eruption of deciduous and permanent teeth + loss of deciduous teeth

Dental Growth

Growth lines

• Use up to age 13 post-natal months.

• Short period lines (24hrs) - cross striations.

• Long period lines (6-12 days) - retzius lines

Radiographs taken

• Use after age 13 post-natal months

Adult age at death

• Degenerative changes

• Age estimation methods

  • Pubic symphysis

  • Dental wear

  Public symphysis:

• Todd - started off with

• McKern and Stewart

• Gilbert and McKern

• Brookes and Suchey - finished off with

Dental Wear:

• Attrition - tooth to tooth breakdown, due to chewing, clenching.

• Abrasion - breakdown of tooth, due to external objects, e.g., chewing on pen, aggressive brushing.

Estimating age at death - adults harder than juveniles

• Age related morphological changes do not progress as regularly.

• Biological processes involved in degeneration of adult skeleton can be influenced by environmental factors, e.g., disease + physical activity.

• Broader ranges for age for adults

  • Results from each estimation should be combined to produce an estimated age range, not a mean value.

Biological Sex Estimation definitions

Sex:

• The biological genotype (genetic material)

• The phenotype (physical form)

Gender = an individual’s self conception, of male or female.

Classic male and female features + examples of joint surfaces

Male:

• Robust cranium

• Brow ridge

• Right angle mandible

• Square chin

Female:

• Gracile cranium

• Sloping forehead

• Long wide angle mandible

• Rounded chin

• Pelvis can be more accurate than cranium, when determining biological sex, as is functional.

• Joint surfaces can be useful when determining biological sex, males ~ robust, more muscular, larger.

Examples of joint surfaces:

Femur

• Diameter of head

• Bicondylar width

Humerus

• Diameter of head

Scapula

• Glenoid cavity

Tibia

• Diameter of shaft

Stature, childhood health, environment of individuals + Trotter + Jacobs

Stature = how tall and large someone becomes

Childhood health:

• Healthy children are more likely to grow bigger, taller.

• Smaller bodies could be sickly children, not necessarily females.

Environment:

• Influences how people grow - industrial vs countryside.

• How body is adapted to environment, location of home, e.g., Peruvians, living in higher altitudes, large torsos, larger lungs to breathe, as less oxygen present at higher altitudes.

Trotter:

• Long bone measurements based on growth standards of American males and females.

• Limitations - body proportions can vary with ancestry, and sickly children can also affect stature development.

Jacobs:

• Measure fragmented section of long bone, add into relevant equations, now have an estimated length of long bone with SE.

Trauma + what it informs us

= acute physical injury or wound

E.g., category - bone fracture

Information attained:

1.) Direction of force responsible for fracture.

2.) When trauma occurred.

3.) Cause of trauma

• Falling, blunt force, sharp object, projectile. (Shows what is present at time of death, not necessarily what caused the death!)

Types of trauma

1.) Partial/complete = part of/all of bone broken

2.) Open/closed = if bone is broken in or out of skin

3.) Impacted = crushing of bone, e.g., falling

4.) Pathological = weakening of osteological system of bone itself, i.e., medical history pre-existing

Types of fracture

Compression:

• Force applied on axial direction, e.g., fall.

• Disease, e.g., osteoporosis.

Spiral:

• Rotational force applied, ‘twisting’ break.

Transverse:

• Force applied at a right angle to bone long axis.

Green stick:

• Considered a part fracture

• Fracture on one side of body only

• Usually sub adult bone, common in children, but heal quickly, as always going through remodelling stage.

Types of cranial trauma

Sharp force:

• Direct blow, linear well defined edges, flat smooth edges, microscopic parallel scratch marks.

Blunt trauma:

• Harder forces causing more concentric cracks on cranium, radiating fractures outwards from initial blow.

Projectile wounds:

• Entrance wound smaller, rounded, more bevelled inwards, radiating fracture lines.

• Exit wound larger, irregular, bevelled outwards.

~ Measure entrance wound, when investigating projectile wounds!

Mortem types + what trauma can inform us

Antemortem:

• Bone remodelling

• Associated disease

Perimortem:

• Trauma colour

• Wound occurred in fresh bone

Post mortem:

• Fresh, clean bone on inside, white.

• Trauma colour

• Wound occurred in dry bone

What trauma can inform us:

• Contribute to biological profile

• Limit ability to create a profile from a skeleton

• Removing indicators of age (teeth)

• Distorting indicators of sex, on skull

• Removing indicators of ancestry, on skull

Disease + Non specific bone diseases

Disease = an abnormal condition that impairs an organism’s function

Non-specific bone diseases (caused by a range of infections):

• Osteomyelitis - infection of medullary cavity.

• Periostitis - infection of periosteum (outer surface)

• Osteitis - infection of compacted bone (in between outer and inner)

Non specific skeletal manifestations

Osteomyelitis:

• Bone formation, bone destruction, pus formation

Sequestrum:

• Localised area of dead bone

Involucrum:

• Layer of living bone surrounding dead bone

Cloaca:

• Opening through which pus is discharged

Leprosy + skeletal manifestations of facies leprosa

Leprosy - infectious disease

Rhinomaxillary syndrome (facies leprosa) - specific infection

• Eats away at bone in sinus part of face, causing soft tissues to degrade.

Skeletal manifestations of facies leprosa:

• Atrophy and disappearance of anterior nasal spine.

• Widening of nasal aperture

• Atrophy and recession of maxillary alveolar bone (incisor region)

• Perforated palate.

• ‘Claw hand’ and ‘claw toe’ deformity

• Resorption of phalanges, taper to points