Forensic Biology and DNA Profiling - Research Paper Example

Forensic biology Introduction Forensic biology is the analysis of biological materials recovered from a crime scene. Forensic biology is primarily aimed at identification of the perpetrators or victims of a crime. Blood, saliva, semen, bones, soft tissues and dental pulp are biological materials that are often analyzed. The process examines the biological material with a view of identifying the source of that material. Forensic biology is necessary in the current case as it is principal in the identification of both the remains and possibly the perpetrators. A proper identification cannot be achieved if a DNA profiling is not conducted on the remains (Butler & Hill, 2012). The first step in investigating the crime is to secure the crime scene. Securing the crime scene assists in reducing interference of physical evidence and reduces the chances of contamination to the crime scene. After securing the crime scene the next step is to conduct a preliminary survey of the area to establish the presence of any other evidence around the crime scene. At this stage it is indispensable to take photographs of the crime scene and collect evidence that may be incidental to the crime. After the preliminary survey is conducted, evaluation of physical evidence is conducted. The evaluation in this case will be to determine the position of the remains, if the remains have been moved by the initial respondents, the condition of the remains and other materials at the scene. After the evidence is evaluated, samples are collected from the remains at the scene. Samples of other biological materials at the scene should also be collected. When collecting the samples from the remains it is important to safeguard against contamination. Contamination occurs when something that was not present is introduced to the crime scene or in the samples collected. Contamination can compromise the analysis and accuracy of samples collected. An effective way of reducing contamination is to limit access to the crime scene which is done by securing the crime scene until evidence is collected and documented. In doing so it is important to restrict the first responders and the law enforcement officers from further access to the scene as they can potentially contaminate the crime scene (Kobilinsky, Levine & Margolis-Nunno, 2009). DNA profiling DNA profiling is a technique employed by forensic analysts in establishing identification of unknown individuals. DNA analysis uses the DNA make-up of the remains to form a profile that can be used for identification. Because the remains at the scene have decayed, visual identification cannot be used and therefore use of DNA profiles can be helpful in identifying the victims. Although it is possible to use the remains, especially the skeletons, to develop a profile on the age and sex of the victims’, positive identification can be obtained primarily from the use of DNA. The process involves the creation of the victims DNA profiles from the analysis of the remains and thereafter cross matching these profiles with profiles of potential victims or with profiles in a database with a view of finding a match. DNA materials are very stable and can stay intact for a very long time and therefore the best method of analysis of the remains in the current case. It is however important to follow proper documentation and preservation standards to ensure reliable results. After the evidence is collected from the scene, it is packaged and transported to the laboratory for analysis (Kobilinsky, Levine & Margolis-Nunno, 2009). The manner the evidence is packaged is important since improper packaging may compromise the samples and affect the accuracy of the results. Proper packaging involves placing different samples in different bags and labeling the bags properly. Labels must also be included on the packages as well as maintaining a proper chain of custody. Proper chain of custody means maintaining a chronological history of the evidence. Once the evidence is packaged and labeled it is then transported to the laboratory or a storage facility as soon as possible to avoid degradation. The manner of transporting the samples is also important as prolonged exposure to heat or humidity may degrade or spoil biological evidence. It is essential to ensure that the evidence is properly packaged in separate bags, sealed, and kept away from heat and humidity and proper chain of custody maintained to render the evidence valuable for analysis (Butler, 2005). Because very small samples of DNA are used, a lot of attention is required to avoid contaminating the samples. A primary contaminant of samples once in the laboratory is cross contamination, where the sample gets mixed up with biological materials from another source. This kind of contamination can occur when an individual coughs or sneezes over the sample or touches the samples with DNA from other parts of his body or other samples. The introduction of contaminants or other materials in the sample will affect the interpretation of DNA results; therefore it is essential to avoid contamination. Effective measures to avoid contamination in the laboratory include using gloves and changing them regularly, especially before handling a different sample. Disposable instruments can also be used and any instrument that is used should be cleaned thoroughly (McClintock, 2014). Analysis of DNA DNA analysis for the decomposing remains will focus on DNA fingerprinting. DNA fingerprinting is a technique that is used to evaluate the genetic information of an individual. The process is referred to as fingerprinting because there are no chances of finding a profile that is similar to another except for identical twins. DNA fingerprinting comprises compilation of a profile from the DNA sequence from the evidence and comparing that profile to known profiles or to profiles of relatives to the victims. DNA fingerprinting is suitable for decomposed bodies because it is only a few cells from the remains that are used to form a profile (Butler, 2011). The specific test conducted in DNA profiling is short tandem repeats (STR) analysis. This procedure uses polymerase chain reaction analysis (PCR) to denature DNA samples into individual strands. The DNA from the sample is then amplified and multiple copies of the target region are obtained. Amplification of the DNA using PCR is necessary where the samples are small and furthermore the process eases the analysis of samples. After the target sections of the DNA are amplified the regions with short tandems are analyzed. The target sections of the short tandems are amplified using PCR and then these sections are compared to short sections of another DNA sample to establish the relationship between the two individuals (Butler & Hill, 2012). Because unrelated individuals have different number of repeats this process can be used to determine the relationship of individuals. The use of STR analysis is a very accurate method of DNA profiling as several STR loci are studied simultaneously and the resulting patterns of alleles give accurate identification. The DNa analysis ca yield three types of results, which are inclusive , exclusoive and inconclusive. Inclusive resulklts implies a positive match between the suspects DNA and that found at the crime scene. Exclusive results precludes the suspect from the crime scene as the DNA between the sample and the suspect do not match. Inconclusive resultrs on the other hand means the results were not sufficient to match the DNA from the sample to that from the suspect (Butler, 2011). Serology is the study of blood and its constituents and these tests depend on antigen-antibody reactions. The conventional methods of serology use polymorphic antigens, enzymes and proteins in blood or other body fluids. Serology can be utilized in individualization and the categories for these tests are serum or protein groups, enzymes and blood groups. Antibodies in blood and other body fluids can be found in decomposing bodies and, therefore, serology can be conducted on the decomposing body. The test that can be conducted in this case is blood typing which is often referred to as ABO typing. Although serological tests can be accurate in identification, the use of DNA is preferred over this method as the earlier method yields more accurate results (Butler, 2005). Issues with the analysis of DNA Challenges that may affect the interpretation of a DNA test are degradation of the evidence. This occurs when the evidence is contaminated and the interpretation of the results can give false findings due to the presence of other DNA apart from the crime scene DNA. Degradation can also occur when the sample is exposed to environments, such as heat and humidity that are likely to destroy the DNA in the samples. Apart from degradation, another challenge is missing DNA profiles. For a positive identification of a perpetrator in a crime, it is essential to match the sample from the crime scene to an available profile in order for the test to be admissible in court. If the profile obtained from the crime scene does not match any other profile, then the test is useless unless an individual of interest or a suspects profile is matched to the profile (McClintock, 2014). Where there is no profile match in the victims DNA, facial reconstruction can be used to identify the victims. Facial reconstruction is the process of recreating the facial appearance of an individual whose identity is not known. Facial reconstruction is achieved by placing layers of facial flesh on the skull of the victim and using proper tissue depth determined by the age and sex of the victim. Available types of facial reconstruction include 2 D reconstruction, 3 D reconstruction and superimposition. Facial reconstruction is significant in the current case since the remains of the victims are skeletal remains or decomposed remains. Since it is possible to have a missing profile of the victims, facial reconstruction can be used to identify victims who lack DNA profile matches (Wilkinson, 2004). A scenario of a court case with the sucesful identification and conviction of a suspect is where the suspects DNA was positively matched to a sample collected from the crime scene. . A positive cross match between the DNA from the sample and that of the suspect signifies similarity in the DNA make up of the two and, therefore, the suspect is the source of the DNA from the crime scene.DNA obtained from a cigarrete butt collected inside the hole where the remains were found places the suspect at the scene of crime. On the other hand, a scenario which would not lead to a successful identification and conviction of a suspect is where the DNA obtained does not match that of the suspect. DNA results that are inconclusive is the reason for the failure to identify and convict a perpetrator. Inconclusve results can result from insufficient DNA materials in the samle as well as contamination of samples. Reference list Butler, J. M. (2005). Forensic DNA typing: biology, technology, and genetics of STR markers. Academic Press. Butler, J. M. (2011). Advanced Topics in Forensic DNA Typing: Methodology: Methodology. Academic Press. Butler, J. M., & Hill, C. R. (2012). Biology and genetics of new autosomal STR loci useful for forensic DNA analysis. analysis, 24(15). Kobilinsky L. F., Levine L. & Margolis-Nunno H. (2009). Forensic DNA Analysis. Infobase Publishing. McClintock J. T. (2014). Forensic Analysis of Biological Evidence: A Laboratory Guide for Serological and DNA Typing. CRC Press. Wilkinson, C. (2004). Forensic facial reconstruction. Cambridge University Press. Read More