Question 4: Let’s uncover the secrets hidden in bones!

So, other than identifying the victim by dental means, what other ways can the identity be revealed? In many criminal cases, forensic anthropology made an obvious contribution in identification of the victim.

Picture from www.forensicscsi.com

Anthropology is the scientific study of the origin, the behavior and the physical, social and cultural development of the humans. Forensic anthropologists are trained to identify human remains along with pathologists, homicide detectives and other specialists.

Roles of a forensic anthropologist:
1. Aids in collection and analysis of human remains
2. Identifies victims beyond recognition (normally victims are examined in the late stages of decomposition i.e. completely skeletonized)
3. Estimates time since death
4. Establishment of injuries and potentially cause of death
“Bones offer amazing clues”
Human remains may give some clues for these aspects:

-Age 
-Age of remains

-Sex
-Ethnicity
-Stature, weight and individual differences
-Facial reconstruction
-DNA

J Age J
As an individual ages, ossification (fusing of separate pieces of bone) occurs in around 800 points around the body. As the bones fuse together, sutures are formed in between them, appearing as ‘zigzag seams’. The fusion of particular bones generally occurs at specific points in an individual’s life. From here, the age of the individual can be estimated.

Bone plate
Around the age of 6, two bone plates form at either end of the radius bone in the arm. The lower bone plate fuses with the radius years later, at age 17 in males and age 20 in females. The upper bone plate follows shortly after. 

Fusing of epiphysis (rounded end of bone) to diaphysis (bone shaft)
Growth centers within the limb bones allow the limbs to lengthen for growth. Throughout this period, the epiphyses are soft, eventually hardening into bone and fusing with the main shaft as adulthood approaches. The head of the femur generally fuses at age 18-20, and part of the hip fuses at around age 24. After this point, the study of this fusing is fairly useless in age determination. 

Cranial sutures (on the skull)
At birth, the human skull is composed of numerous smaller bone segments, their division giving the skull flexibility. As the individual ages, ossification occurs. It is useful in age estimation only if the victim is <30 years old, after which ossification of skull bones is usually complete. 

Cartilage
Some sections of cartilage around the body gradually turn into bone at a particular age (e.g. the wrists). If the victim is < age of 13, a wrist x-ray can often pinpoint the child’s age. 

Pubic symphysis (the midline joint between the left and right pubic bones)
The two pubic bones, joined by cartilage, are characterized by a rough, uneven surface which gradually smoothens out over time.

Osteon counting by microscopy  
Osteons are minute tunnels within the bone housing nerves and nutrient-providing blood vessels. In general, the more osteons present in the bone, the older the victim. 

Dentures, worn teeth, signs of bone degeneration, arthritis, osteoporosis (increased bone porosity) can indicate old age. Tooth eruption date can also help in determining age, particularly in younger individuals.

J Age of remains J
The age of bones can be established by carbon dating. The radioisotope carbon-14 is taken up by humans in life. As the half-life of carbon-14 is known as being 5,700 years, the amount of the isotope remaining in the sample can be used to calculate its age. Hence, time since death can be estimated. This not only narrows down the time frame, but often also the range of suspects. However, if the remains are completely skeletonized, determining time since death based on the bones may be extremely difficult.

J Sex J
The most obvious feature that helps to differentiate between two genders is the pelvic bone. Women generally have proportionally wider pubic bones than men to allow room for a baby’s head to pass through during childbirth. In most cases a female will bear a sub-pubic angle of >90 degrees, whilst the sub-pubic angle of a male’s pubic bone will generally be <90 degrees. The use of the pelvic bone alone has proved extremely precise in establishing sex, with an accuracy of up to 95% (Byers, 2002). However, this is not a useful indicator when determining the sex of a pre-pubescent child, as the pelvic bone in girls is yet to widen, thus meaning there is a lack of sexual dimorphism between the sexes.

The skull is also beneficial in sex determination, though slightly less accurate than the pelvic bone [80-90% using the skull, according to Byers (2002)]. We had discussed about the differences between a male skull and a female skull earlier in Part 1.

Besides, males tend to have larger, heavier, and more rugged bones in general, with slightly larger ends to support stronger muscles. Sex is generally easier to establish if the racial background of the victim is known, due to differences between different ethnic groups.

J Ethnicity J
A Caucasian victim
- narrower face and high-bridged nasal bone
- flat lingual surface in upper incisors
- prominent chin and flat cheekbones

A Negroid victim
- broader nose bridge with wider nasal openings and subnasal grooves
- outward-sloping jaws
- flat lingual surface in upper incisors

A Mongoloid victim
- broader face
- squarer, forward-sloping, wing-like cheekbones
- lower nose bridge
- shovel-shaped upper incisors
- flatter skull 
The morphology of hair between different ethnicities varies. Thus, the structure and colour of any remaining hair may indicate the ethnic origin of the victim. However, the remains of mixed-race victim are likely to display signs of two ethnic groups, making the deduction of race much more difficult.

J Stature, Weight & Individual Differences J
stature identification

-if the skeleton is whole, direct measurement may be used to establish the rough height, with a few inches added to account for flesh.

-established using a formula based around the length of a long bone such as humerus or femur ( Human generally has height two and two thirds length of femur)

-approximated by a measurement from fingertip to fingertip of outstretched arm

Weight

-difficult to establish as layers of fat leave no markings on the bones. However, well developed muscles will leave markers on the bones. ( The more they are used, the rougher the bone’s surface becomes to anchor the tendons of the muscle in use)

-any clothing found worn by the victim may indicate their clothes size and so their weight.

Individual Differences

-through medical and dental records (certain diseases, previous injuries, and birth defects can all leave marks on the bones)

-body implants (artificial hips and breast implants) often hold a unique serial number

J Facial Reconstruction J
It is the method of reconstructing the living face of an individual from skeletal remains.

1.the skull is cleaned of any remaining tissue in preparation for the reconstruction.

2.A number of round, rubber markers are placed at specific points on the skull. (These landmarks are used to indicate the depth of flesh in these locations, their depth being dependent on the likes of sex, age, race, and the presumed weight of the individual.)

3.Strips of clay join these landmarks, with more clay applied in between to act as the ‘flesh’ of the face.(Facial muscles are laid over the flesh, their structures and sizes based on the shape and size of particular facial bones.)

4.External features are then added, such as eyes, ears and a nose. 

5.the skin is coloured and an appropriate hair colour and style selected. 

J DNAJ
If a forensic anthropologist has been called upon, the remains are most likely skeletonised, meaning bodily tissues have decayed. In these situations, it is highly unlikely that nuclear DNA can be extracted. However it may be possible that mitochondrial DNA can be utilised to create a DNA profile. Mitochondrial DNA, or mtDNA, is transmitted through the maternal line, meaning an individual’s mitochondrial DNA originated from their mother. Though not as valuable, mtDNA is much more resilient, and can sometimes be extracted from severely decayed corpses. 

Reference: http://forensicsciencecentral.co.uk/anthropology.shtml