Bones are defined to be rigid organs that constitute part of endoskeleton of vertebrates. Bones are important medico-legally in various aspects. Before bones are to be used for any medico-legal examination, there are certain things to take care of. Many a times, the bones are fragmented, burnt, mixed with wood, or decolorized to such extents that a direct examination of the bone without establishing the following facts would result in wrong interpretation.
- Whether the specimens are bone or not. This may be identified by physical examination, chemical examination or microscopy.
- Whether the bones are human in origin or not. Many a times, bones are recovered in such degraded states that even experts of osteology find it difficult to confirm the human origin with mere physical examination. A chemical test such as precipitin test would come handy in such cases. Bones of great apes are not very different from that of humans and it becomes virtually indistinguishable in the case of the distal carpels, meta-carpels, tarsals or meta-tarsals.
- Whether the bones are from a single individual or not. This is achieved by making a skeleton chart of the available bones. Any disproportion in size or count would point in the direction of multi individual origin. This becomes important in bones that are obtained while digging unknown areas as it might even be from an old graveyard!
Once these characteristics of the available bones are established, the bones may be considered for further forensic analysis. Bones are helpful in forensic medicine in establishing the following facts.
Bones are extremely useful in establishing the identity of the individual of origin. Bones help in this regard because they may be used to establish the following characteristics of the individual of origin:
- Race: This had been observed that there are differences in the anatomy of different races at the skeletal level. For example, the Negro populations of Africa tend to have long femurs compared to the rest of the word. This would mean that a skeleton with an abnormally long femur should remind us to think in that direction.
- Gender: There exist anatomical, physiological and mental differences between the male and the female. It is safe to assume that these differences reflect in the bones as well. The most important of it is the pelvic bone or the hip bone. In females, the pelvic bone should be adapted to serve the additional function of child bearing and delivery and hence will be different from the male pelvic bone. Forensic experts claim that they can state with 95% certainty the gender of the person if the hip bone is provided and with 98% certainty if the hip bone and skull are provided.
- Age at Death: In children, bones serve the additional function of providing a scope for growth. These centers, also called growth centers, close down, or ossify once a specific age is achieved. This age is different for different bones. If there is a full set of skeleton, there opens an option to compare them to determine the approximate age of the person at the time of death. There are other changes in the skeleton that are age dependent, such as fusion of sutures, ossification of fibrous joints, ossification of cartilages, etc. These add to the level of certainty of the age estimation. Advanced microscopy can determine the age at death by looking at the cross section of the bone and comparing calcification levels and patters.
- Dimensions: Legends such as Leonardo da Vinci and Leonardo Fibonacci had already talked about the ratios and proportion on which the human body is built. Modern scientists had succeeded in applying this knowledge to the levels of bones to successfully derive relations between the length of the bones and the dimensions of the person, such as height. There are formulae that can predict the height of a person to astonishing degrees of accuracies from lengths of certain bones. This will add to the knowledge for identification.
- Direct Identification clues: Very rarely, bones provide direct clues to the identity of the person. Consider an example of a person who has undergone a hip replacement surgery. The head of his corresponding femur would always contain the replaced metallic part and would give strong indication to identity, if the skeleton is obtained for identification.
- Source for DNA: We owe a lot to the developments in the field of molecular science. DNA being the basic molecule of life work as the unique unmistakable source of identity. If a body is found in burnt stage, it will be very difficult to identify physically. DNA fingerprinting comes to the rescue in such scenarios, but from where will we collect DNA on a burnt body? Depending on the level of burn, teeth or bones act as sources for DNA. Teeth have got pulp that may be protected from fire by the intrinsic properties of teeth. Similarly, bone can provide bone marrow from which DNA extraction is possible.
Establishing Time since Death
It is very important to establish the time since death of a body, as this stand as a strong evidence in court. In very old dead bodies, the bones are sometimes the only things left from decomposition and the time since death of the body should be extracted from the bones, in such cases. Carbon dating, being the usual method of estimating age of biological specimens is not very useful here, because it had been observed that there is no considerable reduction in the levels of C14 for bodies that are less than 100 years old. Scientists had discovered alternatives such as estimation of levels of certain isomers of nitrogen, estimation of levels of certain amino acids, etc. However, these details give only a rough estimate of the time since death and should only be considered with caution because the levels of biological parameters on a decomposing body are mostly dependent on the surroundings of decomposition.
Establishing Cause of Death
This is ultimately the reason why we do a bone examination. This is most important in cases of exhumations and re-autopsies. In countries such as India, there is no limit to the time after which one cannot do exhumation. This implies that the jurisdiction can always ask for exhumation of a body that was dead hundreds of years ago. In such scenarios, what one will encounter will be mostly bones, and a re-autopsy will consist mostly of bone examination. The details that bones can provide may not be many. It can provide the following information, to start with:
- Toxicological Profile: Levels of various toxins. It is important to compare this with the levels of the same toxin in the surroundings to rule out environmental influences.
- Fracture Profile: Any fracture in the bones that would have been missed in the previous autopsy. Care should be taken to separate this from the natural disintegration of bones.
- Wound Profile: Wounds such as those produced from gun shots are often deep enough to produce marks on the bones. These marks can provide useful insights into the cause of death.
- Organic Profile: Scientists had succeeded in recovering the microorganisms that caused the death, from old fossilized bodies and mummies. Due to the ability of bones to provide a micro environment for the organism to fossilize, bones provide an important reservoir to investigate for the presence of causative organism.