ARCL 228

forensic taphonomy

modifications made to the bone that are essentially natural

effects of animal scavenging

1. scattering/disarticulation of remains
2. pull limbs apart at torso, gnaw an epiphyses
3. break bones in particular pattern by trampling or chewing
- more than 80% of skeleton recovered = less than 6 months since dead
- less than 20% of skeleton recovered = more than 6 months since death
- rodents create parallel lines on bones

carnivore activity on bones

Chewing on bone
- puncturing
- pits (compressed cortical bone)
- scoring (parallel lines)
- furrows (sharp, deeper)
- excessive activity leaving V-shaped marks

sequence of carnivore dismemberment

1. soft tissue of head and neck
2. ventral thorax opened, contents of chest eaten, followed by sternum/rib ends
3. upper limbs
4. lower limbs
5. thorax removed, ribs broken
6. long bones separated from each other
7. all bones disarticulated, scattered, chewed

weathering

water hydrates bone, sun dries it out

burial damage

bone takes on qualities of burial environment
- soil colour permeates bone
- root etching
- erosion of cortical bone
- damage during recovery

water transport phases

1. body sinks, travels away from initial point of insertion
- damage from body scraping, erosion of tissue
- damage from currents
2. body bloats, rises to surface
- body parts begin to separate
3. independent movement of individual body parts
- round segments can travel long distances
- ankles often detach
- flat bones stay closer to point of insertion

Chronological age

birthdays

biological age

growth and development rate
- differs from chronological at actual birth

socio-cultural age

sociological markers from progressing through social stages based on your roles and responsibilities

trajectory effect

dissociation of biological age and chronological age
- nutritional defects

fetal bone growth

starts at 8 weeks, birth occurs at 40 weeks

juvenile bone growth

1. in-utero to 5 years: very rapid (triples in size)
2. 5 to puberty: gradual plateau
3. 14-16: spikes again
- individual and sex dependent

prenatal

conception to birth
- embryo: 1-10 weeks
- fetus: 10 weeks to birth
- birth: 40 weeks, skeleton formed at 32 weeks

infancy

when baby is nursing
- perinate: time of birth
- neonate: first 4 weeks after birth
- infant: birth to 1 year

childhood

weaning (2-5) to puberty
- early childhood: 1-4 years
- late childhood: 5-10 years

adolescence

puberty to end of growth
- early: 11-14 years
- late: 15-17 years

ageing using long bone length

lengths can estimate how long child has been in utero
- varies between people because no everyone is the same

standard error

accounts for differences in bone length between each person

ageing using the skull

- Sphenoid and mastoid fontanelle: after birth
- Posterior fontanelle: 6 months
- Anterior fontanelle: 1-2 years
- Metopic suture: 2-4 years

ageing using vertebral arches

2 years: neural arches fuse together
3-4 years: pedicals fuse to neural arches

ageing using sacrum

2-6 years: neural arches fuse
12-14 years: lateral element fuses
12-25+ years: sacral vertebrae fusees

ageing using scapula

18-20 years: acromion process fuses
16-17 years: coracoid process fuses
15-20 years: rim of glenoid fossa fuses

ageing using humerus

14-21 years: hemeral head fuses (F=14-19, M=16-21)
11-18 years: distal epiphysis fuses (F=11-15, M=14-18)
13-18 years: medial epiphysis fuses (F=13-15, M=16-18)

ageing using radius

11-17 years: radial head fusing (F=11-13, M=14-17)
14-20 years: distal epiphysis fusing (F=14-17, M=16-20)

ageing using ulna

12-16 years: olcranon fuses (F=12-14, M=13-16)
15-20 years: ulnar head fuses (F=15-17, M=17-20)

ageing using hand and wrist

ageing using femur

12-19 years: femoral head fusing (F=12-16, M=14-19)
14-18 years: greater trochanter fusing (F=14-16, M=16-18)
16-17 years: lesser trochanter fusing
14-18 years: distal epiphysis (F=14-18, M=16-20)

ageing using tibia

13-19: tibial plateau fusing (F=13-17, M=15-19)
14-19: distal epiphysis fusing (F=14-16, M=15-18)

ageing using patella

appears at 3-6 years

ageing using fibula

12-20 years: proximal epiphysis fusing (F=12-17, M=15-20)
12-18 years: distal epiphysis fusing (F=12-15, M=15-18)

ageing using foot

ageing using teeth

- ex. M1 Tooth: 1/4 length grown = 4.9 years
- ex. I1 Tooth: 1/4 length grown = 4.8 years

tooth eruption

adult or deciduous teeth as they are being exposed through gum line

adult age

1. young adult: 20-35 years
2. middle age: 35-50 years
3. old adult: 50+ years

bones that fuse in adulthood

1. clavicle: 16-30 years (manubrium end)
2. sternum: 40 years (xiphoid process, sternal body)
3. sacrum: 25 years (sacral element 1-2)
4. os coxa: 27 years (pubic symphysis), 17-23 (iliac crest)

adult bones breaking down

- pubic bone - pubic symphysis, auricular surface (gets more holey, coarser, striations, more stable joint)
- ilium
- ribs - surface bone, surface contour, rim contour
- cranial sutures (fill with bone)

pubic symphysis degradation

rib degradation

primary sex characteristics

genitals

secondary sex characteristics

skeletal and phenotypic forms that develop during puberty

female secondary sex characteristics

- mechanisms necessary for childbirth
- juvenile growth rate faster

male secondary sex characteristics

- taller on average
- muscle attachments larger

estimating sex

more sexually monomorphic than other species
- pelvis: correct 90-95% of the time
- skull: correct 80-90% of the time
- long bones: correct <80% of the time

sex estimate with nuchal area

m: rugged, may have hook
f: smoother, rarely have hook

sex estimate with mastoid process

m: large, projecting
f: small, non-projecting

sex estimate with brow ridges

m: large
f: small to none

sex estimate with supraorbital margin

m: rounded
f: sharp

sex estimate with mental eminence

m: broad or square
f: pointed

discriminant function equation

M1: cranial length
M2: cranial breadth
M3: bizygomatic diameter
M4: mastoid process length

sex estimation using pelvic inlet

M: heart-shaped
F: circular/elliptical, parturition scarring

sex estimation using subpubic angle/concavity

M: narrow or V-shaped
F: wide or U-shaped

sex estimation using ilium

M: tall, denser
F: broad, thinner

sex estimation using pubic bone

M: narrow, rectangular
F: broad, square

sex estimation using pre-auricular sulcus

M: absent/poorly developed
F: present/well-developed

sex estimation using greater sciatic notch

M: narrow
F: wide

sex estimation using coxal bone

- ventral arc: M=slight/absent, F=strong
- subpubic concavity: M=convex, F=concave
- ischiopubic ramus ridge: M=broad/flat, F= narrow/crest-like ridge

three main classifications of ethnicity (problematic)

black, white, asian

nose anthroposcopic traits

1. root
2. bridge: how far nose sticks out
3. spine
4. shape of lower boarder: edge of nostrils (sharp, flat, or no boarder)
5. shape of nasal aperture (tall, oval, heart-shaped)

face anthroposcopic traits

- face width: narrow or wide
- eye orbit: angular, rectangular, rounded

suture anthroposcopic traits

- sutures: patterns are complex and unique
- post-bregmatic depression (where coronal and sagittal suture meet): not always present

jaw and teeth anthroposcopic traits

- jaw shape: parabolic, elliptical, hyperbolic
- chin shape: small, large/pointed, blunt,
- teeth: crowding, gaps, incisor shapes

Carolus Linneas

created the Homo sapiens classification - white, black, dark, red

Johann Blumenbach

first to use comparative anatomy
- 5 categories: Mongolian, American, Caucasian, Malayan, Ethiopian

sharp force trauma

wounds left on the bone from bladed instruments

* narrow focus, dynamic, slow-speed compressive
* sometimes resembles blunt force trauma

SFT cleft

deep/wide v-shaped cut

SFT wastage

removal of bone from inside of cleft

SFT punctures

penetrating wound

* captures shape of object

SFT striations

lines etched into bone from passage of blade

* parallel to cut mark
* perpendicular = chopping motion

SFT incisions

gradually tapered v-shapes

* longer than they are wide

wound analysis

1. Wound Description

* placement on skeleton


* type of wound
* size


2. Instrument Characteristics
* Type
* Blade
3. Direction of Force
4. Number of Traumatic Events
5. Sequence of Events

Antemortem Injury

healed sharp force trauma

* rounded edges

Blunt Force Trauma

elevated level of impact, not high velocity

* characterized by radiating fracture lines
* type of instrument influences wound seen

BFT instrument size

focused = smaller objects

diffused = wider objects

BFT shape of instrument

cross-sectional outline

longitudinal configuration

* injury mimics shape of object

deformation

inbending and outbending at impact site

elastic bone fracture

incomplete - more resistant to forces, more collagen, most often inward bending

brittle bone fracture

complete fracture - whole sections of bone may fail

weak trabecular bone fracture

incomplete fracture - outer table fail, inner table might not

weak inner table

comminuted fracture - inner table fail, outer may not

depressed skull fractures

break in cranial bone, depression towards brain

spiderweb skull fractures

radiating lines on outbent surface

* additional force used


* stop at suture or previous radiating line
* tend to have bone wedges in-between fractures

skull bone wedges

concentric fracture lines and bone wedges forced inward

hinge skull fractures

incomplete fracture on one side of depression

* outward bending not completely separating

face fractures

3 areas (denser to weaker facial sections - buttressing)


1. alveolar ridge
2. malar eminences
3. nasofrontal processes

lefort fractures on the face

LeFort 1: between alveolar and nasofrontal

LeFort 2: between nasofrontal and malar

LeFort 3: below anterior temporal and midfrontal

* most frequently occurs in high-speed car accidents or falls, or striking the face directly with a rigid object

cranial vault fractures - 4 areas of buttressing

1. Midfrontal
2. Midoccipital
3. Posterior temoral - mastoid process
4. Anterior temporal - above sphenoid

ring fractures

falling backwards on hard surface, jumping from large heights and landing on feet

* skull base fracture
* spine shoved into crania

long bone BFT

* complete fractures
* bone wedges
* parry fractures (when you block trauma with your arm)

wound analysis

1. Wound description

* Placement on skeleton, bones being impacted
* Type of fractures


2. Estimate size of instrument
3. Estimate shape of instrument
4. Estimate direction of blows
5. Estimate force
6. Estimate number of blows

* Flaking on edge of fracture = multiple blows to same area


7. Estimate sequence of trauma

* First blow will have greater range of radiating fracture lines
* Fracture line that extends the most without being impeded will be first line


8. Miscellaneous estimations

* Intrinsic factors of bones, combination of tools used, different shaped trauma indicating different weapon areas, health issues

BFT ribs

most common cause of rib fractures

* direct pressure on ribs = break

BFT vertebrae

most often caused by car accidents - also assault, hanging injuries, sport injuries

BFT scapula

caused by significant BFT - 75% car accidents

BFT pelvis

uncommon in instance of BFT (8-9%) - often car accidents/being hit by a car

burning - stage 1

pugilistic posture

* initial evaporation of moisture in body
* heat induced bending of limbs at joints

burning - stage 2

soft tissue modification

* flesh chars/splits
* hair burns off
* expulsion of cooked internal organs
* larger muscles take longer to burn off

burning - stage 3

bone modification

* collagen chars first
* bone reduced to mineral
* denser bones take longer to modify

bone burning colour change

* Low Temperature (200-700 C): yellow brown to darker yellow brown to black
* High Temperature (+800 C): dark grey to lighter grey/blue to white (calcination)

bone burning bone cracking

* crescent shaped along diaphysis - transverse cracking on long bones
* shape relates to speed bone is drying out

bone burning hydrated bone

longitudinal breaks