DNA Analysis in Forensic Science

    As technological advancement takeover the world, the field of criminology and forensic science has not been left behind. There has been increased application of DNA technology in the forensic science casework over the last few years. The use of biological evidences in the scene of crime has transformed forensic science making it more accurate and able to solve cases other evidences have been unable to solve. By use of DNA analysis, the identity of the perpetrator of a crime can be identified with a lower degree of uncertainty. This has been valuable especially in case where the suspect is involved in violent criminal acts where no eyewitnesses are available. The development of DNA analysis in forensic science gained momentum in the second half of the 20th century and has since been instrumental in solving major criminal activities all over the world.

    DNA analysis in forensic science has since become an acceptable scientific advancement all over the world and is considered very sensitive and therefore it is essential in the modern world. Federal security agencies such as the FBI have for that reason developed index systems with databases which provide data for comparison of the suspected criminal profiles. The database contains millions of profile of convicted criminals and thousands of profiles from crime scenes and has aided in the investigation of thousands of criminal activities. Moreover, the United States government has established two federal and forty nine state forensic laboratories dealing with DNA analysis (Dale, et al, 2006).

DNA analysis in forensic science
    For many years, the only physical evidence that could be used to identify the suspect with the scene of crime was comparison of the hidden fingerprints on the scene and the suspects fingerprints. Looking for fingerprint from the files in the absence of the criminal suspects was both a demanding and tedious process. This led to the development of an Automated Fingerprint Identification System, which solved the problem of manual search for the matching fingerprint as well as the need for the suspect in the process. The use of AFIS technology increased the accuracy involved in identification of the suspect with the crime scene. A database was also developed which was thought to be a breakthrough in forensic science due to the rate at which criminals could be identified with great precision (Wickenheiser, 2002). 

    However, the advent of DNA analysis and profiling opened a new chapter in forensic science. The link of biometric information of the suspect with the crime scene has brought unimaginable dimensions in forensic science. Three decades ago, forensic technologies used ABO blood typing techniques in forensic science to rule out or include individuals in the suspects lists. Over the years, forensic science has advanced progressively to more reliable and accurate DNA analysis techniques. In the past, the use of ABO blood typing and electrophoresis could categorize and thus exclude the suspected individuals but could not be depended upon as a method of positively identifying the criminals (Dale, et al, 2006).

    The structure and the possible importance of DNA in living organisms was first proposed in the 1950s by two scientists, Watson and Crick. However, the successful use of DNA in forensic science was developed in the mid 1980s.

    The use of DNA typing in the investigation of crime in the crime scene was first introduced in 1980s and it is clear that it has transformed forensic science since then. Today, the law enforcing agencies are able to match the criminals and the scene of crime more accurately. Many cases have been solved as well as guiltless suspects gaining their freedom, thanks to the biological witness which is now easy to obtain from the scene of crime. DNA profiling was first developed by an English scientist Alec Jeffreys in the mid 1980s. The scientist noted a unique pattern in every individuals studied DNA. He noted that a certain section in the individuals DNA was repeating itself and was unique for every individual. He was able to develop his observation to a technique that could be used to identify individuals from their DNA materials. This repetitive region in the DNA strand is called the variable number of tandem repeat which is commonly abbreviated as VNTRs. The technique used by this English scientist to examine the repeating regions in the DNA was called RTLP (restriction fragment length polymorphism). The method was useful is solving several cases such as the English immigration and double homicide. In the last two decades, there has been tremendous development in DNA analysis with application of different field of human identifications including crime and parentage (Jeffreys, et al, 1985).

    Although the use of RFLP and VNTR was seen as a powerful technological advancement in forensic science, it had some setbacks which led to the improvement of forensic DNA analysis. The technique was costly and consumed up to eight weeks to give results. This basically was a lot of time. The procedures involved were also risky because of the healthy hazards involved since it used radioactive probes. The technique also required relatively large amounts of material for analysis which had to be intact and was unavailable in many crime scenes.

    As a result of these shortcomings, better molecular techniques such as polymerase chain reaction, PCR were developed. PCR was developed in 1986 and has since played a major role in amplification of DNA materials collected in small amounts at the scene of crime. PCR is a very sensitive technique and can synthesize and replicate large amounts of DNA molecules for analysis from the traces collected at the scene of the crime. The technique has the ability of producing millions of DNA molecules from one template in three hours time. This is because each molecule synthesized serves as a template in the subsequent synthesis. PCR techniques require the law enforcement agencies to collect traces of the suspects blood, semen or saliva at the scene of the accident which will then be analyzed to develop evidence against the suspect.

    Since the development of PCR in the mid 1980s, other techniques of forensic analyses based on DNA have been developed. This includes the mitochondrial DNA or the mtDNA technique. This technique is based on material outside the nucleus of the cell. The material is available in relatively better volumes compared to the DNA material in the nucleus and is less vulnerable to damage in the environmental. This technique is more applicable since the profile of the suspect can be developed from cells such as hair shafts which do not contain nucleus. It is applicable in solving cases that involves degraded human tissues such as decomposed bodies. However, this technique provide a less accurate statistical probability, it is expensive and consumes more time in sample preparation and analysis. These limitations are hoped to reduce with the increased automation of the processes as well as efficiency as a result of economies of scale.  

    The usefulness of mtDNA is instrumental in the modern forensic science due to its ability to obtain a statistical probability from specimen that may not yield any profile using other techniques. For example, if the specimen available consists of charred material, it is almost impossible to develop a profile using other techniques but mtDNA can easily be applied in such cases. This is because in many cases, it is possible to obtain sufficient material from any remains which can be used for mtDNA analysis. The information required for this technique is therefore not affected by physical or chemical changes of the specimens. Another feature that of these technique which makes it superior is in the ability of mtDNA to be inherited from the mother. The feature makes it applicable in tracing the remains of a lost person where the reference of the analysis is derived from the missing persons relative. The mtDNA profile of sibling who shares the same mother has some similarity.

    Mitochondrial DNA profiling has been used in several case studies in the United States and other parts of the world to solve historical forensic confusions. This technique has been used successfully in the identification of soldiers who fought in Vietnam War and Second World War. These case studies involved comparing the material from their distance relatives with the remains of the soldiers. These case studies were successfully used to identify the remains of Tsar Nicholas II by comparison with materials from his family. Other case studies include identifications of missing individuals and casualties in disasters involving mass such as the 911 attack.

    In the past few years, the main focus in the development of DNA analysis technology has been in increasing sensitivity threshold by improving the PCR amplifying technique to sense even lower levels of DNA material. The improvement of any of the techniques always results into increased benefits on its adequacy. Improvement of the technique results in more accurate profile as well as a reduction in the overall time consumed in the preparation and analysis of the samples. PCR technique has since been improved to STRPCR technique (single tandem repeat polymerase chain reaction technique) which gives a more conclusive report as compared to the previous technique. Due to this improvement, forensic science laboratories have been able to develop profiles from despoiled materials using the DNA techniques, for example in the TWA flight 800 disaster (Butler, 2005).    

    Following the 911 attack by terrorists, the federal forensic science laboratories received major challenges on their ability to solve forensic cases. In this particular case study, the forensic community was faced with the job of analyzing large volumes of despoiled samples. To increase the sensitivity, single nucleotide polymorphism techniques as well as mtDNA techniques were used to develop the victims profile. All the personal effects which belonged to the terrorist attack victims were collected by detectives and analyzed. The data was then compared with the profiles developed. The personal effect data was compiled in the forensic center located in Albany while the victims profile was developed by the chief medical examiner in New York. The two laboratories collaborated in the development of a network system to aid the identification of the victims. A good number of the victims were positively identified although most of the samples have not yet been analyzed. The unanalyzed samples have been stored in controlled system to avoid degradation as the forensic scientist wait for the development of more advanced forensic techniques (Presidents DNA Initiative, 2006).

    There is even more hope in the development of better and more sensitive techniques. Modern technologies which have not been fully developed are in the final stages of development such as Low Copy Number may be a breakthrough in the fields of forensic science. In the future, detectives may be able to develop the DNA profile of a suspected criminal from the fingerprints on the scene of crime. This could be done using technology which develops the profile from the skin cell in the fingerprints. This can be used to back the evidence collected and the statistical probability developed using other forensic techniques. The DNA profiles developed using the fingerprint may be very useful incase the sample obtained in the scene contains degraded DNA materials which may not be easy to develop a DNA profile.

    There is also hope of development of modern laboratory kids which can be used by forensic scientists at the scene of crime. Therefore, in the future, highly trained detectives may be able to develop the suspects profile right at the scene of crime using portable chips with better precision. Research is currently going on in the development of such portable and sophisticated ultramodern forensic equipments. Recovery of physical evidence at the scene of crime and timely processing of the data may be instrumental in the reduction of doubts about the identity of the suspect. Through the use of such techniques, the suspect profile will be developed automatically at the scene of crime and circulated through the security database and it will be easy to trace and arrest the suspect.

    Towards the end of the 20th century, FBI sponsored an index system that is today used by 177 laboratories in the United States. This index system which is known as the Combined DNA Index System was a pilot project where fourteen states participated. The national DNA indexing system is administered by a memorandum between the FBI and the states and all forensic laboratories are expected to support the index system. The use of DNA analysis has not only been used to solve crime cases against people but also use in pets. DNA analysis of animals has been useful in case the suspect was accompanied by a pet or an animal in the crime scene. Forensic institutions have also developed missing persons database using different DNA analysis techniques (Dale, et al, 2006).

    The contribution of DNA analysis in forensic science since the potential role of DNA was suggested in the mid 20th century has been unimaginable. It has been used as evidence in law courts where innocent individuals have been released and prime suspects in crimes being identified. After the first successful use of DNA profiling in the mid 1980s, more interest has developed on the usefulness of this technique. It has been successful in various case studies such as profiling the 911 victims, identifications of soldiers who died in wars and other disasters. However, research is underway in the development of more efficient forensic techniques.


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