September 11, 2001 was a day that started like any other. With winter soon approaching, it was a time to enjoy the last of the nice weather with nothing on our minds but another meeting, another homework assignment to do, another business trip to prepare for. For most, it was a day that would pass just as quickly, just as naturally, and just as forgettable as any other day, or so we thought. It was on this day that "the sleeping giant" was once again shaken from its rest and rattled to the core. It was a day that will never be remembered as just another day, for it was the day where thousands lost their lives, their families, their opportunity to breath the air of 'another day'.
What occurred on the day the Twin Towers was destroyed was an event that defined the term mass disaster better than any recent event in my lifetime up until that point. Even with the fear, heartache, and anger that rose, it was important to remember that identification of the victims was necessary in order for families and friends of loved ones to obtain closure to their grief (Okoye and Wecht 2007). Under these conditions, especially for the 9-11 attack, identification of individuals were extremely difficult due to the scattering of body parts and the fact that sections of victims were blown into tiny pieces. However, this problem was solved with the use of DNA typing. As the key ingredient for all living organisms, DNA is a biological source which requires our undivided attention (Seager and Slabaugh 2000). Its chemical makeup is unique to every individual, with the exception of identical twins, and therefore provides the information needed to make a clear distinction between individuals (Seager and Slabaugh 2000).
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DNA was collected from each piece of biological material found at Ground Zero and then compared to the families of the victims to obtain a match to someone believed to be at the site the day of the attack. As the collection pile grew, the hours, days, weeks, and months also grew. Finding, testing, and matching all the material collected to a specific individual was no doubt a daunting and meticulous task, especially with almost 3,000 fatalities. However, the task continued with the help of numerous forensic scientists aiding in the identification process.
When a mass disaster occurs, the recovery of an entire body is difficult to do. Even so, there are several ways to uncover an identification of the remains that are collected by using DNA. Biological material (tissue, bone, blood, ect.) is left behind when people die and is a crucial source of evidence that can be collected and used for identifying those casualties lost in a mass disaster (Okoye and Wecht 2007). The biological material that is collected from the remains at the site of the disaster is then compared to those lost during the devastating event (Okoye and Wecht 2007).
The techniques that are used to retrieve DNA from the small pieces collected after a disaster include "resin based DNA extraction, real-time PCR, use of mini-STRs, (and) SNP detection procedures" (Budowle et al. 2005). Mitochondrial DNA can also be used in some cases where sample fragments are compared to the mothers of the victims (Butler 2005). The process that these techniques follow varies, but in general, identification using DNA is a very clear-cut method (Okoye and Wecht 2007).
Polymerase chain reaction, PCR, is performed in three steps. These steps include denaturation at 94 degrees C, annealing at 60 degrees C, and extension at 72 degrees C. Denaturation is the process of using heat to break apart the double helix of the DNA template. The template is the original sample that you want to copy. Annealing adds primers to the complimentary pairs at opposite ends of the separated helix. Extension uses DNA polymerase, an enzyme, to extend the primers and complete the replication process in order to accomplish the goal of copying the original DNA. This method is very useful for mass disasters, because only a small amount of DNA is needed to start with and then replication can occur as many times as necessary for an analyst to obtain a useable sample for identification (Butler 2005).
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Short tandem repeats, STR, is a newer version of PCR that was developed to help profile and visualize the DNA that was amplified (James and Nordby 2009). STRs are analyzed using PCR to amplify the specific regions of alleles for comparison (James and Nordby 2009). There are four nucleotides or base pairs that comprise the double helix. These nucleotides can be in any order, but when these bases are grouped in four, that makes up a sequence. If sequences of four nucleotides are repeated over and over in a strand of DNA, then the numbers of repeats are counted and used to find a positive or negative match among missing individuals. In order to measure the number of repeats, capillary electrophoresis is used and the sample is inserted in an agrose gel (James and Nordby 2009). The information is interpreted by a computer and peaks are revealed for a DNA analyst to interpret the output. These peaks indicate the presence of an allele on a specific locus (James and Nordby 2009). Although DNA between any two humans is 99.7% identical, this method is successful because the likelihood of finding two people with the same number of repeats within the same loci is 1 in 32.4 quadrillion (Rudin and Inman 2002). This frequency is calculated using the product rule where the number of allele frequencies on a loci are multiplied together to determine the probability of individuals with the identical genetic makeup (Rudin and Inman 2002). The STR method is very useful for degraded DNA because "the size of DNA fragments produced by amplification of STR loci is in the range of 200 to 500 base pairs" (Rudin and Inman 2002).
Single nucleotide polymorphisms, SNPs, are used for comparison between two individuals as well. SNPs are favorable in the forensic community, because the method is well suited for degraded DNA and there is a greater ability to multiplex the sample using SNPs rather than STRs. The process consists of using a specific area in an individual's genome to find variation in single based sequences. The abundance of SNPs in an individual is about 1 in every 1 kb, therefore they play a large role in differentiating between individuals. The downside of this method is that the sample needs to contain several alleles in order to achieve a discriminatory power high enough to distinguish between two individuals, because there are only two alleles on each locus. Therefore, 25-45 is the average amount of SNP loci needed to acquire acceptable results (Butler 2005).
Mitochondrial DNA, mtDNA, is also a great source taken from biological material to help identify victims of mass disasters. This is because compared to other biological materials, mtDNA is a reasonably secure source (Rudin and Inman 2002). In order to examine mtDNA, a sample collected must be amplified using PCR and then sequenced using fluorescent dye (McCurdy 2007). Forensically, mtDNA provides a very influential tool for acquiring the necessities needed to identify someone, however this source of DNA is unable to differentiate between those with similar DNA, such as siblings. This problem is caused due to the fact that mtDNA is a DNA source inherited only from the mother and therefore siblings would acquire the same genetic inheritance, making it difficult to distinguish between certain individuals (James and Nordby 2009). Although useful, this type of DNA profiling is only used if absolutely necessary due to an increased risk of contamination (Butler 2005).
Although technology has helped enhance the possibility of identifying an individual by using DNA, problems still exist. Mass disasters create such astronomical damage that biological specimens that are collected at the casualty site are not highly suitable to provide faultless information (Okoye and Wecht 2007). Using our example of a mass disaster from above, the following issues were problematic; DNA was burned due to the crash of the airplanes, it was degraded due to extreme heat caused from the fire which was created by the jet fuel and from the gallons of water used to try and put out the flames. The samples that were collected for possible identification were most likely highly contaminated due to being mixed with airborne pathogens from the rubble or chaos occurring, and possible decomposition of samples due to environmental factors not already enhanced by those at the site (Okoye and Wecht 2007). These samples are found to be useless once testing reveals low peak levels that are not comparable to what would be expected from a DNA sample (Okoye and Wecht 2007). These problems not only cause frustration, but also uncertainty in the identification process.
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What occurred on that dreadful day was devastating to our entire nation, but good has come out of the bad. The event provoked the forensic science community into improving the methods used for identification. After the terrorist attack, a computer system was created to help in the identification process specifically for mass disaster situations. This program was developed by Howard Cash, president of a bio-informatics firm called Gene Codes, based in Michigan. This firm, before 9-11, produced software that was used by scientists who worked on the Human Genome Project. Cash and several of his employees aided in the identification process conducted at Ground Zero by providing a software program called M-FISys, mass fatality identification system (Lovgren 2003). This program has aided in "rewriting the science on DNA mass identification" (Lovgren 2003). M-FISys was able to identify victims by "direct match algorithm and helped in collapsing and sorting data sets to obtain identifications" (Butler 2005). The software was able to take the data collected "from three different DNA tests on human remains and compare them to DNA samples taken from victims' kin and genetic material" (Lovgren 2003). This information was given within minutes rather than weeks, which was how much time it took before Cash's program was created (Lovgren 2003). By decreasing the time it takes to obtain an identification, the total output of overall identifications can increase tremendously. These types of technologies that contribute to the forensic field has allowed for an enormous advancement as well as time and cost efficiencies, which play a major role in the field.
Although the process for crime scene management remains the same for every case, mass disasters make it very difficult to follow protocol due to the numerous individuals involved and the chaos that occurs. Contamination risks are very high because of this and positive identification may become difficult. Even so, it is very important that the identification process become a priority for those involved.
The identification process conducted after the 9-11 terrorist attack was "the most difficult ever undertaken by the Forensic Science community" (Sanders 2006), because of the degree of damage caused. The success of hundreds of individuals identified was possible due to the enormous effort put forth by volunteers within the community. It was also possible because of the technology that has improved the use of DNA typing for identification purposes.
Although not all of the 2,749 victims of September 11th were identified (Butler 2005), DNA typing allowed for hundreds of families to find peace in knowing the finality of their loved ones. September 11th was only one example of many where DNA was a great contributor to the forensics field and where the identification of thousands of individuals were revealed from the minute pieces of evidence that was collected. Found in every cell throughout the body, DNA is the key to providing evidence necessary for discovering the identity of individuals. It is for this reason why time should be invested to uncovering the knowledge it is capable of providing and to create any means necessary for improving the methods involved in such processes.
- Budowle, B., FR. Bieber, AJ. Eisenberg. Forensic Aspects of Mass Disasters: strategic considerations for DNA-based human identification. 7(4): 230-43.
- Butler, John M. Forensic DNA Typing: Biology Technology and Genetics of STR Markers, 2nd ed. Elsevier Academic Press, New York, USA.
- James, Stuart H., Jon J. Nordby. Forensic Science: An Introduction to Scientific and Investigative Techniques, 3rd ed. CRC Press, Boca Raton, FL.
- Lovgren, Stefan. Rewriting the Science on DNA Mass Identification. National Geographic. 5 May 2005.
- McCurdy, Leslie D. Multiplex PCR electrospray-ionization mass spectrometry (ESI-MS): application to forensic mitochondrial DNA examinations. Forensic Sci Int-Gen. 01:052-054.
- Okoye, Dr. Matthias I., Dr. Cyril H. Wecht. Forensic Investigation and Management of Mass Disasters. Lawyers & Judges Publishing Company, Inc., Tucson, AZ.
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- Sanders, Catherine. Department of Justice Issues Guidance for the Use of DNA Identification in Mass Disasters. (http://www.ojp.usdoj.gov/).
- Seager, Spencer L., and Michael R. Slabaugh. Chemistry for Today: General, Organic, and Biochemistry, 4th ed. Brooks/Cole, Pacific Grove, CA.