Forensic Anthropology Revision PDF

Preview

Summary

Lecture notes for the full FZ2051 course, including diagrams and citations. Revision necessary for the end of year exam and practical spot tests....

Description

Anthropology Revision Comparative anatomy: Quadraped:  

Animal with four limbs Mostly vertebrates

Biped:   

Animals with two rear limbs All birds are bipedal Primates can exhibit sustained bipedalism

The mammalian axial skeleton:       

Open eye sockets laterally Mastoid processes are small Occipital modified for large neck muscles attachment Foramen magnum posterior Elongated nasal area Mandible is usually two equal halves which are unfused No chin

Vertabrae:           

Orientated for quadrupedal locomotion – spine parallel to substrate Five types of vertebrae Different number of types – 7 cervical, 12 thoracic, 4-6 lumbar, 4-6 sacral, and many caudal Human have wedge shaped vertebrae with larges bodies from neck to pelvis Mammals have more cylindrical vertebrae with bodies of similar length Cervical vertebrae modified to support gravitational pull of the head Articulation of C1 with the occipital condyles is deeper Thoracic vertebrae have longer spinous processes to support the nuchal ligaments ‘Cantilever’ system to support head Lumbar vertebrae have transverse processes which are longer relative to the body Caudal – up to 50 depending on tail length

Pectoral girdle:  

Clavicle maintains distance between sternum and scapula and provides support for shoulder girdle Present in humans and other animals that use forelimbs for manipulation or require forelimb strength and dexterity and in birds

        

Scapula is elongated in most nun-human mammals with the glenoid fossa at the end of the long axis Scapula located dorsolateral in quadrupeds All animals have a round humeral head In quadrupeds, it is weight bearing so more massive, especially the proximal shaft Animals that require speed and flexibility have separate ulnae and radii, as humans Some non-human mammals have fused ulnae and radii, or have significantly reduced ulnae to make rotation impossible Many large animals have reduced number of digits Distil phalanges are normally claws in small mammals and hooves in large mammals In some animals metacarpels are fused (metapodial bones)

Pelvic girdle:      

Due to changes in the ilium, centre of gravity is different in quads and bis Lower limbs of quads have little lateral motion Strength of muscles in the leg benefit from a long pelvis Femur has a more sculpted anterior distal articular surface in nonhumans In many nonhumans the tibia and fibula are fused, or the fibula is lost Distal articular surface of the tibia is more sculpted in nonhumans

Sea mammals:  

Adapted to life in water Skeletal morphology can be markedly different to terrestrial mammals

Bird or baby bones:   

Confusion because immature human long bone articular surfaces are ‘unsculpted’ Bird bones have thinner cortex and are very lightweight Bird bones are ‘pneumatic’ – part of the respiratory system

Teeth:      

Incisors – chisel shaped cutting teeth at the front of the mouth Canines – long-cone shaped teeths sitated behind incisors for holding and killing prey Pre-molars are transitional teeth between canines and molars Molars are grinding teeth at the back of the mouth Herbivores have no upper incisors or canines, have large ridged premolars and molars, and have a sideways jaw motion so molars grind over each other Carnivores have enlarged canines for gripping and killing, smaller incisors, some pre/molars are adapted to cut flesh, and have a shorter and robust jaw



Rodents have absent canines and incisors adapted for gnawing (very long and self sharpening)

Sex estimation using the pelvis: As we evolved to bipedal the pelvis changed shape; especially for females to accommodate foetal growth whilst standing. Pelvis widened in response to increased weight pushing down The Phenice Method:    

1969 Proposed the use of the ventral arc, sub pubic concavity and width of ischiopubic ramus 95-96% accuracy Revised by Klales 2012 – created an ordinal scale so ambiguous traits could be incorporated

Not all traits are as reliable (GSN and OF are variable) Metric methods pose problems in some cases. However, more accurate than skull as not affected by morphology or population. Sex estimation using the skull: Most of the features used on the skull are muscle attachments and because of this, males tend to have larger pronounced features than males. Ferembach 1980:   

Based on correct classification rates from each feature Some traits are more diagnostic than others Method combines weight, with an ordinal scale score to provide a vaule for determining sex

Williams and Rogers 2006:  

Looks at improving methods for sex estimation to make them compliant with court of law requirements Some cranial traits are more diagnostic than others and provide better accuracy

Age can impact on morphology – younger skulls look more feminine. Population can also impact on morphology.

Age at death estimation using epiphyseal fusion:

Developmental changes – ossification, growth, epiphyseal fusion, and dental development  

Occur over predetermined timescales Growth and development can be affected by specific stresses such an nutrition or pathological stress

Degenerative changes – wear and tear and structural changes  

Take place over larger timesclaes Subject to greater variation

Intramembranous bone formation:  

Formed from mesenchymal tissue with no cartilaginous precursor Clavicle, mandible, frontal, parietal, facial bones, vault portions of the temporal, occipital and sphenoid

Endochondral bone formation:      

Formed from cartilaginous precursor All other bones form via this method Cartilage model is produced, periosteum forms around model, osteoblast secrete osteoid against the cartilage shaft Primary areas of ossification are the areas where ossification begins In long bones, the diaphysis in the primary ossification centre and the epiphysis are secondary Most primary centres develop prenatal – initiation of primary ossification is related to the presence of associated nerves

Epiphyses:   

Growth plate (metaphysis) ceases growth and ossifies and fuses the epiphysis to the diaphysis In dry bone, unfused epiphyses are separate elements Use fusion charts by Scheuer and Black, 2000

Dentition:       

The tooth surface which touches the tongue is the lingual side The surface touching the cheek is called the buccal side or labial side for the anterior teeth Mesial refers to the surface of the tooth facing along the arcade towards the median Distal refers to the opposite; facing along the arcade away from the median Occlusal refers to the chewing surface Apical refers to the apex of the root Comprised of three mineralised tissues: enamel (95% hydroxyapatite), cementum and dentine (70% HA) which surround a central pulp





Dentine is the tissue that forms the core of the tooth, the crown is coated in enamel, and the root is coated in cementum from which the periodontal ligaments arise (attach tooth to bone) Apical foramen is a tiny opening at the root apex for nerves and blood vessels

Incisors:     

Flattest teeth with a cutting surface Crown shape is spatulate Maxillary are broader than mandibular Lingual surface is concave Lower incisors are more chisel shaped whilst upper and shovel shaped

Canines:   

Tusk like with pointed occlusal surface Upper canines are broader than lower canines Lower canines have less developed lingual features

Premolars:  

Premolar have two cusps and rounder crown shape Upper premolars have strong median grooves

Molar:     

Crowns are larger and square, with 3-5 cusps Upper crowns tend to be rhomboid in shape 3rd molar crowns are the smallest with more irregular crown positioning Upper molars have three roots Lower molars have two roots

20 deciduous teeth precede 32 permanent teeth: 8 incisors, 4 canines, and 8 molars Mineralisation:     

Correlation between tooth mineralisation and age At birth, all deciduous teeth and first permanent molars have started to mineralise Age estimation combines crown and root mineralisation with emergence By 3 all deciduous teeth have emerged and roots have mineralised From 6-12 years, permanent teeth replace deciduous teeth

Teeth are highly resistant to degradation and survive well, however, alveoli do not, therefore fragmented skulls and loose teeth are very common. Teeth lost antemortem will result in the resorption of alveolar bone. Forensic dental anthropology: focus on profiling the skeleton for age and race estimation. Forensic odontology: focus on matching evidence of dental surgery and pathology with dental records to identify individuals and to assess sustained trauma. Adult age estimation: Certain joints are more accurate for age estimation; these are the less mobile joints. Cartilage in these joints allow slight and subtle movement; when this cartilage is gone we can see similarities in the patterns left behind on the bone between individuals. These patterns are studied and contextualised against age estimation; there is a predictable pattern to a series of categories. Using the pubic symphysis: Key features of the PS are:     

Ventral and dorsal borders Superior and inferior extremities (borders) Superior and inferior demi-faces Ventral and dorsal demi-faces Symphyseal rim

Todd (1920) was the first method for estimating age from PS. Discovered that patterns appear to correlate with age. Based on a sample of 306 males of known afes. Distinguished 10 phases in which an adult could be places. However, small age ranges lead to error, and derived from only males! McKern and Stewart (1957) updated Todd’s method. Noted variation in dorsal plateau, ventral rampart and symphyseal rim. Each component can be given a separate score and added to form a composite score which is then assigned to age ranges. However, sample was again all male (n=349), and ages only applied up to 50 years of age. Brooks and Suchey (1990) applied the previous method to females and found it unreliable. They worked to refine Todd’s method into fewer phases which meant wider age ranges to minimise error, and allows for broader observation so reduces interobserver error. They used modern skeletons of both males and female. They also decided that females reach later stages earlier, possibly due to child birth.

Pubic symphysis is often damaged by scavenging or during excavation, and surface damages if not stored correctly. Maceration techniques to remove soft tissue have also been shown to impact bone surface. Pathology can also affect the pubic symphysis and this means if pathology is present it should not be used for age estimation. Using auricular surface: Key features:    

Superior and inferior demi face Apex Pre-auricular sulcus Retroauricular area

Lovejoy (1985) were first to associate surface texture changes to age. They described specific features and applied them to narrow age ranges. However, some features appear in more than one age category, narrow ranges mean more error, and shown to be less affecttive in older bones.

Osborne (2004) revised Lovejoy and broadened descriptions to remove overlap and increase age ranges which increases accuracy and usability.

Less prone to damage than the pubic symphysis, however does require more maceration to access surface due to its protection. Both methods are based on visual elements so are subjective. Also affected by population, however appears to be consistent against multiple populations. Using 4th rib: Morphology of sternal end is used for age estimation; this is due to costal cartilage that allows thorax elasticity. Iscan (1985) – revised in 1993. Key features:    

Surface bone (smooth, granular, or porous) Surface contour (billowy, indented, v-shaped, or u-shaped) Rim (rounded or sharp) Rim contour (straight, undulating, or projections)

Using cranial sutures: Meindl and Lovejoy (1985) – degree of closure of ectocranial sutures. 1. 2. 3. 4.

Open – no closure Minimal – some evidence of closure Significant – marked degree of closure but still some not completely fused Obliteration – complete fusion

Ancestry Race - Morphological assessment:

and

Caucasoid – Europe, Indian sub-continent, North Africa, and the Middle East. Negroid – Sub-Saharan Africa Mongoloid – Asian outside Indian sub-continent, Native American and Inuit. Australoid – Australian aborigine, and Pacific islanders. Lewontin: 

1972

   

Cited as evidence that differences among human groups are too small to allow accurate classification 85% of variation is found within populations, 8% within populations of the same race or regional grouping, and 6% is found among races or religions Overlooked the fact that some markers are significantly correlated with others and therefore are not independently distributed among groups Edwards (2003) confirmed Lewontin as correct at the single locus level, but multiple loci reveal a more realistic picture of among-group variation

Ancestry and Race – Metric Methods:   





Gall (1758-1822) developed cranioscopy Lombroso (1835-1909) anthropological criminology 14 identified traits of a criminal – large projecting jaw, low sloping forehead, high cheekbones, flattened or upturned nose, handle-shaped ears, hawk-like nose, fleshy lips, and small shifty eyes Retzius (1796-1860) cephalic index to classify ancient remains: Dolichocephalic (long and thin), Brachycephalic (short and broad), and Mesocephalic (intermediate length and width) Lapouge (1899) hierarchy of dolichocephalic Aryan race, and mediocre and inert Brachycephalic

Craniometry: Technique of measuring the bones of the skull; measures linear distances between anatomically defined points, angles between anatomical structures, or subtenses. Measurements can be directly compared (statistically) or mathematically transformed. Stature Estimation:

Forensic stature (FSTAT) is self-reported. Males overestimate by about ½ inch, females by ¼ inch. Taller people over estimate less, whilst older people overestimate more. Height reduction is not accounted for. Failure to update is a source of error. Biological stature is measured stature (MSTAT). Interobserver error. Diurnal variation. Age related stature loss. Sex affects age related loss. Cadaver stature (CSTAT) is greater than standing stature, by approx. 2.5cm. Secular change is pone that is continuous and non-periodic – Meadows and Jantz (1995) showed that there has been an increase in lower limb long bone length and longer tibiae. Populations differ proportionally in statute, however, lower limb correlates more strongly in all populations. The use of population specific equations is important – use generally across all populations would result in too large an error. Bogin and Loucky (1997) showed that Mayan children born and raised in Guatemala were shorted than Mayan children born and raised in the US – major phenotypic differences. Anatomical method of stature estimation:     

Dwight (1894) Reconstruction of a skeleton using clay Enables accurate reconstruction of spinal curves and disc spaces, other soft tissue spaces, and allows for scalp and heel pad. However, this requires a whole skeleton and is very time consuming. This was revised in 1956 and added up measurements from individual bones and added a correlation factor to account for soft tissue – not practical for forensic use though.

Mathematical method of stature estimation:   

Pearson 1899 Uses linear relationship between long bone length and stature To calculate: factor x length in mm + constant = ??? +/- 90%PI

Generally, long bone length provides lower margins of error than other skeletal elements. However, in cases where skeletal elements are limited, other elements may be useful. All equations are based upon work using specific sample sets – there may be population or group specific considerations. Projectile Trauma: Careful and thorough trauma analysis is essential to prove evidence or cause of death. Subject to deposition environment and post mortem interval, degradation of skeletal elements may eliminate evidence of trauma. Knowledge of the mechanics of trauma is essential.

Ante-mortem trauma – characterised by signs of healing and important for medicaleal and identification reasons. Peri-mortem trauma – specific fracture characteristics (broken edges are angled and jagged, and surfaces and sharp and irregular and often hinging. Staining on or around the fracture from haematoma. Formation of fracture lines from the point of impact. Important for medico-legal circumstances surrounding death. Postmortem damage – rarely exhibits radiating fractures, broken ends are flat and at right angles, and broken ends are frequently lighter in colour. GSW to the cranium:      

Entrance is smooth and rounded margins on the outer table, the inner table is bevelled around the margins Radiating fractures may propagate from the entrance hole Concentric heaving fractures may develop around the entrance hole between the radiating fractures Exit hole exhibits smooth margins on the inner table, has a larger hole compared to entrance, and is ragged on the outer table Exit wounds may produce radiating fractures, however these will stop at preexisting fracture lines so sequence of entrances and exits can be made Key hole defects occur if the bullet enters and exits at an acute angle to the bone

Blunt, sharp and hacking trauma:       

Tension Compression Torsion Bending Shearing Speed of force Focus of force

Blunt force: Typically sustained from low-energy impacts resultings from a broad instrument delivered over a large surface area. Most blunt force injuries result from vehicular accidents of falls. The severity and appearance depends on: 1. 2. 3. 4. 5.

Amount of force used Time over which the force is delivered The region struck Extent of the body surface hit Nature of the weapon

Could be abrasions, contusions, lacerations, and fractures. Inbending will occur at the site of impact with outbending at some distance from this point. Sharp force trauma: Analysis may provide information about the direction of the cut, handedness and the type of tool used. What should you record? 1. 2. 3. 4. 5. 6. 7. 8. 9.

Shape of the cut mark – linear or irregular? Cross section of the cut mark Characteristics of the walls of the defect – smooth or serrated? Characteristics of the floor of the defect – smooth or serrated? Depth of the feature Presence of hilt Presence and shape of defect Presence of associated fractures with defect Presence of crushing associated with cu mark or defect

Cut marks are shallow linear striations on the surface of the bone which generally have a V-shaped cross section and are caused by a sharp or bladed instrument. Peeling or shaved defects result when a blade strikes bone at an angle and a piece of pone is lifted from the surface, or can be caused by torsion. Point insertions or notched defects are penetrating injuries in which only the tip of the instrument hits the surface of the bone. Slot fractures occur when a shopping wound penetrates the skull and often results in multiple fractures as the blade is removed. Chop marks are caused by long and thick bladed instruments with one cutting edge. They cause disruption to the continuity of the bone and cause chattering by fracturing the edges of the bone it impacts. Scoop marks chara...