Identification of Unknown Bodies using DNA - Research Paper Example

Running head: IDENTIFICATION OF UNKNOWN BODIES USING DNA Identification of Unknown Bodies using DNA Insert Here Insert Affiliation Here Identification of Unknown Bodies using DNA The identification of an unknown body is perhaps one of the most daunting tasks for forensic detectives. The obscurity of the task further multiplies when the bodies to be identified belong to victims of mass disasters, catastrophes, gruesome murders and accidents, in which they are deformed or decayed to a large extent. Traditionally, fingerprints have been used for the forensic identification of individuals for a long time, yet they have their own limitations. They are easily deformed due to injuries and scratches, and even suffer from the risk of being misinterpreted. Owing to technological advancements, fingerprint analysis has now been replaced by DNA (Deoxyribonucleic acid) analysis. Like fingerprints, the DNA of every individual is unique. This fact can be exploited for the determination of the identity of an individual by studying his/her DNA. DNA from hair, skin and nails, or even traces of semen or blood holds the key for the successful identification of a body, through the technique of DNA fingerprinting, also called DNA profiling or typing. DNA fingerprinting has been in use in forensic science since the time of its inception, and has helped in the identification of criminals, missing persons, murder victims and even ancient bodies. This paper discusses how forensic detectives use DNA to identify unknown bodies. A brief history of DNA analysis is also reviewed. A few incidents in which unknown dead bodies have been successfully identified based on DNA analysis are also discussed. I. Use of DNA for Identification A. Why DNA? As indicated earlier, the DNA of every individual is unique. About three million bases, equal to “one-tenth of a single percent of DNA”, varies among individuals (BERIS, 2009). These variations can be analyzed to determine a person’s DNA profile from samples such as hair, nail, blood, tissues, semen or any other specimen that contains his/her nuclear or mitochondrial DNA. Trace amounts of a sample are usually sufficient to carry out DNA analysis. Furthermore, in case of deformed or decayed bodies and even corpses that have been buried for a long time, DNA is the only available source for identification as the bodies are damaged beyond recognition. In some cases, the body parts of a victim of a gruesome murder or a mass disaster (both natural, such as hurricanes and earthquakes, and man-made, such as bomb blasts or a plane crash) are burned or charred, and sometimes are even separated from one another. Most military casualties are also unidentifiable. Traditional methods of identification such as those involving fingerprints and odontology (dental records) require intact fingers and jawbones of the victim along with his previously recorded and documented fingerprints and dental records, to enable their comparison and subsequent identification of the victim (Butler, 2009, p. 404). In absence of these samples and records, DNA analysis is the method of choice as DNA can be extracted from any sample of the body, even from traces of tissues or blood from clothing or other material. Minute quantities of DNA can be amplified using the Polymerase Chain Reaction (PCR). For the identification of an individual, about 13 regions/loci of DNA are examined for creating a DNA profile. Except for identical twins, the odds of two individuals having the same DNA profile are negligible, about one in a billion (BERIS, 2009). B. History of DNA Analysis – DNA Fingerprinting/typing/profiling Alec Jeffreys, an English geneticist was the first to describe DNA fingerprinting in 1985 (Butler, 2009, p.4). He observed that certain sequences in some parts of the DNA repeat over and over again. The fact that these repetitive sequences, now called VNTRs (Variable Number of Tandem Repeats), vary in length among different individuals gave rise to the possibility of using these variations for identifying and differentiating one individual from another. Alec Jeffreys developed a technique that could be used to examine variation in the length of these repetitive sequences (VNTRs), thereby enabling “human identity tests” (Butler, 2009, p. 5). The technique used by Jeffreys was Restriction Fragment Length Polymorphism (RFLP), in which, the DNA region surrounding the VNTRs is cut using restriction enzymes and the VNTRs are then analyzed. The fragments of repetitive sequences are used to create a DNA profile/fingerprint of an individual, which is unique to him and does not match with any other human being. Although this technique was the first to be used in DNA analysis for forensic investigations, it is rarely used anymore because of the large amounts of sample required for it. Another drawback of this technique is that samples of DNA that are degraded by environmental factors cannot be easily analyzed (BERIS, 2009). DNA analysis using RFLP is thus being replaced by other advanced techniques discussed below. C. Other Methods of DNA Analysis Technological advancements have enabled the evolution of other technologies using DNA for the identification of unknown individuals. 1. STR (Short Tandem Repeat) Analysis Using this technology, short repeating sequencing in DNA, called STRs can be examined. These regions vary from one individual to another, and these variations can be used to distinguish between different individuals. The Federal Bureau of Investigation (FBI) uses thirteen STR loci as a standard set for DNA profiling (BERIS, 2009). 2. Mitochondrial DNA (mtDNA) Analysis This technique is used to analyze the DNA isolated from mitochondria, when nuclear DNA is unavailable for RFLP or STR analysis (BERIS, 2009). This technique is helpful for analyzing samples from hair, teeth and bones, when tissue or blood samples are not available. The cells in hair, teeth and bones do not contain nuclei, and so, nuclear DNA cannot be extracted from these samples. While identifying very old bodies that have been decaying for a long time, hair, bones and teeth are the only source of DNA. In such cases, mt-DNA analysis has helped in identification of the unknown bodies. Mitochondria are transferred from the mother’s egg cell to an embryo. Therefore, unlike nuclear DNA, which is transferred from both the parents to their offspring, mitochondrial DNA is transferred only from the mother. Therefore, mt-DNA analysis can be used to establish maternal relatives and identify unknown bodies by comparing their DNA with probable mothers or maternal relatives. 3. Y-Chromosome Analysis Y-Chromosome analysis involves the analysis of the Y-chromosome, which is transferred only from a father to his son. Just like mt-DNA analysis that is used to trace maternal relatives, Y-chromosome analysis can help in tracing male relatives for identification, and also for analyzing biological samples containing DNA from many males (BERIS, 2009). D. How Unknown Bodies are Identified by DNA Analysis As already discussed, DNA is the most preferable sample for determining the identity of an unknown body. Given below is a stepwise description of how forensic detectives identify an unknown body using DNA: 1. Procurement of the sample For the identification of dead bodies using DNA analysis, teeth are very good sources of DNA, in the absence of tissue samples and blood. Teeth are very useful for DNA analysis even in a highly decomposed condition (as cited in Minaguchi et al, 2005, p. 146). Apart from teeth, DNA samples can also be obtained from hair, skin, bones, tissues and blood specimens. 2. Extraction and Quantification of DNA The DNA is extracted from the biological specimen using standard DNA extraction procedures or those suggested by DNA extraction kits. Once DNA is extracted from the biological source, the quantity of recovered DNA is estimated (Butler, 2009, p. 8). 3. Amplification of STR markers using PCR Once the DNA has been isolated from the cells and quantified, it is subjected to Polymerase Chain Reaction (PCR). This is done to amplify the regions of DNA that contain STR loci. Millions of copies of the desired regions can be obtained using PCR. The same procedure can be used for amplification of mtDNA and Y-chromosome too. 4. Examination of PCR products and construction of DNA profile The PCR products containing many copies of the desired DNA regions (13 STR loci in this case) are then run on agarose gel for separation based on size. The separated DNA fragments appear as bands on the agarose gel. Fluorescent DNA probes are designed to bind to specific complementary sequences of STR alleles, also known as markers, on these DNA bands. The binding pattern of a series of probes to the sample DNA is unique to every individual. This distinctive pattern is called a DNA profile (BERIS, 2009). 5. Comparison of DNA profile to population databases or probable relatives for determination of identity For carrying out the identification of an individual, apart from DNA samples of the body, the individual’s previously archived DNA profile should be available. This is required because once the DNA profile of the body is obtained, it has to be compared with other DNA profiles to get a match, so that the identity of the person can be ascertained. For the identification of criminals, the DNA profile of the sample obtained at a crime scene is compared with the DNA profiles of suspects or with DNA profiles stored in a database, such as CODIS. The CODIS database (COmbined DNA Index System) is a National DNA Databank of the United States, containing the DNA profiles of criminals. If the DNA profile obtained from the sample procured at a crime scene matches that of the suspect or with any one of the DNA profiles present in the CODIS databank, it can be said with certainty that the sample DNA belongs to the suspect or to a criminal whose data is stored in the CODIS databank. This makes it easier to identify criminals. However, in case of unknown bodies, it is difficult to find a DNA profile with which the DNA of the unknown body can be compared or matched to ascertain its identity. This problem reduces to a certain extent because of the availability of missing persons’ databases. When a person goes missing, his/her DNA is acquired using samples of hair, skin etc from hairbrushes, razors, toothbrushes and other such utilities frequently used by the missing person (Caesar, 2009). A DNA profile of the missing person is then stored in a database. In addition, the DNA profiles of other relatives of the missing person are also stored. When an unknown body is found, its DNA profile is compared to those found in the missing persons’ database. If the DNA profile of the unknown body matches a DNA profile in the database, the person can easily be identified. Several cases of missing persons have been solved this way. Absence of archived DNA profiles makes the identification of an unknown body difficult. Databases that include DNA profiles of the entire population will be helpful. However, the development of such a database is still a distant possibility. II. Instances where DNA Analysis has been used for Identifying Unknown Bodies There are innumerable instances where DNA analysis has been successfully used for the identification of unknown bodies. A few such instances are discussed here. Identification of Victims of September 11 – DNA analysis has been used for the identification of victims of the September 11 disaster of the World Trade Center in the United States. Twenty thousand victims were reported as missing, and the figure came down to 2753, later on. Yet, there is still an uncertainty in the “total number of dead” (Kirby, 2011). Of the 2753 reported victims, 1585 had been identified using DNA analysis. Identification of Jeffery Dahmers Victims – Jeffery Dahmer, a psychopathic serial killer, has been accused of killing more than 15 males (Caesar, 2009). Body parts such as skulls and penises of his victims were the only evidences available. DNA analysis from these sources revealed DNA profiles that matched with most individuals in the missing persons databases, leading to a successful identification of the victims to whom the body parts belonged. Thanks to DNA analysis, “the young men could be given a name and a burial” (Caesar, 2009). Identification of remains in the Tomb of the “Unknown Soldier” – The remains in the Tomb of the “Unknown Soldier” were found to belong to First Lieutenant Michael J. Blassie from the United States Air Force (Butler, 2009, 387). This identification was done by analyzing mitochondrial DNA obtained from the remains. The mtDNA in the remains was a close match with that of Jean Blassie, Michael’s mother. Successful identification of unknown bodies has helped in the closing of many hitherto open cases of missing persons and mysterious corpses. While DNA analysis and the use of DNA databanks have proven beneficial to forensic scientists and detectives, speculations on their misuse abound. Moreover, the use of only a few STR loci for identification is condemned on the basis that these loci are fairly limited, and so, the conclusions are “probabilistic” (Cho & Sankar, 2004). While the creation of more precise technologies and vast DNA databanks are still underway, DNA profiling will continue to solve innumerable forensic mysteries. References BERIS. (2009). DNA Forensics. Biological and Environmental Research Information System (BERIS), U.S. Department of Energy Genome Program. Retrieved 2011, September 25, from http://www.ornl.gov/sci/techresources/Human_Genome/elsi/forensics.shtml. Butler, J.M. (2009). Fundamentals of Forensic DNA Typing. Massachusetts: Academic Press. Retrieved 2011, September 25, from http://books.google.com/. Ceasar. (2009, June 24). DNA Used To Identify Jeffery Dahmers Victims Parts. UnsolvedMysteries.com. Retrieved 2011, September 25, from http://www.unsolved-mysteries.com/forensics/dna_jeffery_dahmer.html Cho, M. K., & Sankar, P. (2004). Forensic genetics and ethical, legal and social implications beyond the clinic. Nature Genetics, 36(11 Suppl), S8-S12. Nature Publishing Group. Retrieved 2011, September 25, from http://www.nature.com/ng/journal/v36/n11s/full/ng1594.html. Kirby, T. (2011). Mechthild Prinz: using DNA to identify the victims of 9/11. The Lancet, 378(9794), 868. Retrieved 2011, September 25, from http://www.thelancet.com/journals/lancet/article/PIIS0140-6736(11)61401-3/fulltext. Minaguchi, K., Maruyama, S., Kasahara, I., Nohira, C., Hanaoka, Y., Tsai, T., Kiriyama, H., et al. (2005). Identification of unknown body using DNA analysis and dental characteristics in chest X-ray photograph. The Bulletin of Tokyo Dental College, 46(4), 145-153. Retrieved 2011, September 25, from http://ir.tdc.ac.jp/irucaa/bitstream/10130/244/1/46_145.pdf. Read More