Forensic Information Retrieved From Bones
Forensic anthropology is a sub-field of physical anthropology that has medico-legal implication (Dayal, et al. 2008). Forensic anthropology then has two main branches: studies of ancient cultures, and the legal forensic science application. The two respective branches are studied with many of the same technologies and purposes in mind. The human participation in both arenas has always been great, but with the advent of better technology methodologies have improved. Many characteristics such as behavior and lifestyle may be inferred through bone analysis. Also, anthropological examinations of a skeleton with accurate measurements of various bones may help determine age, the sex, and to a limited degree, the probably racial origin (Kade, et al 1967). It is for this reason the following paper draws heavily from ancient cultural research while maintaining the forensic science application.
Divisions of the bones into three categories aids systematic study of bones found at the scene (Eakins, 1980). There are flat bones: the pelvis, scapulae, ribs, sternum, and skull, tubular bones: long and short bones of the arms, hands, legs, and feet, and finally the irregular bones: including vertebrae, knee caps, and other small bones of the wrist and ankle (Eakins, 1980).
Habitual activity, behavior tendencies, and or evidence of trauma are another type of evidence that can be recovered from bone analyses. Trauma to bone, including cutmarks and or fractures suggests behavioral aspects of violence and or circumstances of death (Milner 1995). Ostearthritis patterns in joints and skeletal hypertrophy of major muscle attachments have allowed researchers to reconstruct past activities or occupations of the deceased (Boyd, 1996). However, judgments on behavior tend to be speculative in that assessing the pain suffered by is difficult and determining that individual's personality is impossible from just bones. Identification by characteristics which show a wide range of natural variation may be as conclusive, though less dramatic, than identification by fracture, disease etc (Brues, 1958).
There are two methods used in determining statue from bone remains: anatomical methods, and the mathematical method. The anatomical method estimates total skeletal height via the sum of skeletal elements (cranium, vertebrae, femur, tibia, talus, and calcaneus) and subsequently corrected to attain the living stature (including the soft tissue) (Dayal, et al. 2008). The main disadvantage of the anatomical method is that a nearly complete human skeleton is required for an accurate estimation of stature (Dayal, et al. 2008). The mathematical method places bone length measurements into regression equations of skeletal height or living stature (Dayal, et al. 2008). The advantage of such a method is that measurements obtained from a single bone could be extrapolated to give desired information. However, the main disadvantage of the mathematical method is that different regression formulae are required for different populations, different bones, and also for each sex (Dayal, et al. 2008). Regression formulas derived from the major long bones are considered most accurate (Dayal, et al. 2008). However, correlations (between bone calculations and actual height, tend to be greater where combinations of bone rather than a single bone (Dayal, 2008).
Estimates of sex, skeletal analysts typically record features indicative of morphological dimorphism most notably in the pelvis bone (Geller, 2005). This dimorphism is present due to the fact that females give birth and males do not. Therefore female arcs and sciatic notches are greater. In the adult the skull is the second most helpful portion of the skeleton for determining sex (Eakins, 1980). In general, concerning the rest of the skeletal bones, robusticity tends to characterize males and gracility females (Geller, 2005). Other bones, particularly the sternum, may provide useful information, but in the absence of the pelvis or the skull, sex is often impossible to determine with certainty (Eakins, 1980.)
Racial characteristics are grouped into three classes: those which are apparent only in soft tissues, those apparent both in soft tissue and bone, and finally those apparent only in bone (Brues, 1958). The first class is easily identifiable, eye color, skin pigmentation, shape of eyelids and lips, if the soft tissues are present. However, often these soft tissues are not present to make such a determination. The second class of features is that of the contour of bone around the root and bridge of nosean area in which racial differences are especially developed (Brues, 1958). The last set of characteristics apparent only in bone examinations includes: the formation of the lower border of the nasal aperture, very distinctive in reasonably full-blooded Negros or extra suture lines in respective skull races (Brues, 1958).
Age determination is used more frequently in anthropological endeavors, but can be extremely useful for forensic endeavors as well. For non-adult individuals assessment of the bone growth development, and the formation or eruption of teeth can lead to accurate age determinism (Aykroyd, et al. 1999). However, estimating the age of an adult skeleton is more problematic (Aykroyd, et al. 1999). "Age determination is ultimately an art, not a precise science"- a cautionary tale for biological anthropologists when determining age in an adult skeleton (Aykroyd, et al. 1999). The primary problem with such an Endeavour is that: once all the bones of the skeleton have developed and all the teeth have erupted the body will start to degenerate but that degeneration will not occur at the same rate for everybody; disease, diet and physical activity, for example mat all affect how fast or slow a body (and its skeleton) ages (Aykroyd, et al. 1999). Individual human beings, unlike other animals, exhibit many varied eccentricities in behavior, diet, and or routine. The (bone) pubic symphysis is probably the most commonly used (and most widely trusted) method of age estimation when that part of the pelvis is present (Aykroyd, et al. 1999). Results of age determinism are certainly more reliable when it is possible to combine a wide range of age indicators, including a mixture of skeletal and dental indicators (Aykroyd, et al. 1999).
All of the aforementioned feature estimates are not identifying characteristics because of the fact that shape, size, and general contours of one or more bones may be similar in different persons of the same sex, age, and body build (Kade, H. et al. 1967). However, x-ray examinations of the details of bone structure will reveal individual characteristics which may be compared in the same way fingerprints are compared in the establishment of identity (Kade, H.et al 1967). This x-ray analysis is conducted more routinely with comparing teeth and jaw x-rays with that of available dental records. Nevertheless, x-ray examination of bone structure may provide a means of positive identification when compared with x-rays taken during life (Kade, H. et al 1967).
Ultimately identification is the strongest when distinctive features are identified between physical evidence and prior records or subsequent reference samples of the suspect. The teeth may present many features valuable for identification (Brues, 1958). If an individual has had good dental care, the dentist should have a detailed record of work done on the teeth, including the number of fillings, which teeth they are in, and what part of the tooth (Brues, 1958). Each one of those features add to quite a convincing identification case, especially is those features are present at several respective teeth. Unfortunately, many people participating in acts of crimes and deception might fall from the social class which regularly attends a dentist. The value of teeth in these cases is limited to information obtainable from those who knew the individual in life, or from photographs (Brues, 1958). However, the true value of identification via teeth is when the teeth are the most distinguishing feature of the corpse remaining. The identification of charred, mutilated or decaying corpses is made possible only through examinations of the teeth (Klein, 1929). It is of the utmost importance in recovery of the corpses and in clearing off of the dust and debris after a fire to collect carefully loose teeth, bridges, full dentures with metal plates, and other parts which may be of value in identification (Klein, 1929).
Forensic archeologists along with forensic analysts seek human identification. Deoxyribonucleic acid (DNA) is one of the most discriminative tools available for identification. However, the forensic archeologists will have little success in extracting DNA from such old bones. Mitochondrial (mtDNA) is the most commonly extracted form of genetic code material from ancient specimens such as Neanderthals (Machugh, et al. 2000). The forensic analysts will reap the same benefits as the forensic archeologists due to the characteristics associated with the nature of mtDNA itself: The mitochondrion organelle and its associated small circular genome (16kb approximately) is present at a very high copy number in most cells (usually 1000-10,000 copies as opposed to 2 DNA copies) (Machugh, et al. 2000). Excluding mutations, mitochondrial DNA is identical for all maternally related relatives (recombination does not occur as in DNA) (Allen, M. et al. 1998). A higher success rate with tying mtDNA, as opposed to nuclear DNA, is expected and experiences due to the high copy of mtDNA (Bogenhagen & Clayton 1974). In addition to the high copy number; mtDNA is preferentially protected (kept generally sterile) in bone due to the durability of the bone tissue (Machugh, et al. 2000). Mitchondrial DNA is typing useful in forensic identification, normally for samples of shed hair or charred remains, which are often recovered at crime scenes and which contain little or no nuclear DNA (Wilson, et al. 2003). Mitochondrial DNA analysis has been performed successfully in many other applications too: mtDNA has been successfully typed from saliva from stamps (a noted DNA poor source) (Wilson, et al. 2003).
Albeit mtDNA has drawbacks: mitochondrial DNA suffers from a serious drawback in a forensic setting: because of the absence of recombination, the mitochondrial DNA sequence of two apparently unrelated individuals can be identical, or very similar, owing to shared inheritance from a common maternal ancestor, possibly many generation in the past (Wilson, et al. 2003). This makes it difficult to assess the evidential weight of matching mitochondrial DNA profiles in a way which is fair but makes efficient use of the data (Wilson, et al. 2003). Hence, organizations such as the UK Forensic Science Service (FSS) employs mitochondrial DNA minisequences consisting of 12 loci in the mitochondrial DNA control region that displays a high level of genetic variation (discriminatory power) while being relatively quick to type (Wilson, et al. 2003). Various statistical models exist to attempt to quantifiably assess the chance of these many mtDNA base pair similarities. The stand coalescent is a stochastic model resulting is a genealogical tree representing the ancestral relationship between samples of mtDNA sequences (Wilson, et al. 2003). Additionally, mtDNA is maternally inherited, and it is mandatory to be used in cases where relatives by the maternal side are accessible to give reference samples (Andelinovic, et al. 1994).
In conclusion, there is a vast array of information which is retrievable from bones of a crime scene. Mitochondrial sequencing provides only another useful tool for characterizing biological evidence (Allen, et al. 1998). Of course, the types of evidence sought in each individual forensic case would vary on the details of the case, conditions of the body (level of degradation or assault) and the circumstance of the case overall (amount and types of supporting evidence). Because the forensic lab has so many choices in processing the evidence; leadership, forethought, and organization is paramount to the execution of an excellent investigation. The every expanding repertoire of tools available for the forensic analyst should be seen as an asset. It is also important to note that no single forensic method alone will solve a case. Conversely, each piece of evidence should support the other in some form and strengthen the overall case being presented for either the prosecution or that of the defense lawyers.
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