Trace Evidence and Methods Used to Properly Collect Trace Evidence, Blood and Biological Evidence - Essay Example

trace evidence and the methods used to properly collect trace evidence, blood and biological evidence Forensic science is currently regarded asa very powerful and reliable professional field that deals with the analysis and identification of individuals that may be associated with a criminal case (Hunter, 2006). The field of forensic science generally deals with the application of specific and highly sensitive techniques that allow the forensic analyst to identify both the victim and the assailant of a criminal case. The main material employed in forensic analysis cases is any biological material that is present at the scene of the crime. These materials may be in the form of blood, hair, skin or any other samples that are primarily derived from the human body, such as sweat, saliva or mucous secretions. The main biological molecule of target for forensic analysis is deoxyribonucleic acid (DNA), which is present in all cells of all organisms. Biological evidences at the scene of the crime thus serve as essential resources for DNA that could be employed in the forensic analysis of a criminal case. DNA from cells of both the victim(s) and the assailant(s) may be extracted from biological materials that are collected from the crime scene. With the proper application of molecular biology techniques, DNA could be extracted from forensic samples and subjected to DNA analysis. The main procedure employed in the analysis of DNA is the polymerase chain reaction, which is an enzymatic process that generates several copies of DNA based on the sequence of a template DNA (Giardina et al., 2009). The reaction involves a bacterial enzyme that has the capacity to withstand high temperatures that are required for DNA amplification. The amplified DNA fragments are then subjected to a separation assay called agarose gel electrophoresis, which mainly involves running the DNA according to its molecular weight in the presence of an electric field. The fragments are then expected to migrate through the gel and stop at its corresponding molecular size. Both the victim and the suspect's DNA samples are subjected to the polymerase chain reaction, as this will allow the identification of the source of each biological material that is collected at the crime scene. The most common DNA sequences involved in forensic analysis are the short tandem repeats (STRs), which are usually between 20 to 100 nucleotides in length and highly variable in the human population. It is thus expected that every individual in the human society may carry a different sequence in the STRs and the only other individuals that could have a match with a person are those of his parents or his children. Other biological materials that could be collection from the scene of a crime include insects, as well as pollen, that may be present on and within the body of the victim. It should be understood that a human body immediately undergoes the process of decomposition within the first hour after the individual dies. Insects deposit eggs within the first few hours of death and these develop into larvae, or maggots, that are often observed in a body that has been left in the open for a couple of days (Nazni et al., 2008). Forensic entomology allows the researcher to identify the species of the larvae, as well as to determine the age of the larvae in terms of developmental stages or instars. This estimation plays a critical role in determining the time of death of the victim. The presence of pollen on the body of the victim of a criminal case may also provide information on whether the victim was murdered at the site or was otherwise transferred from one place to another. Every place has a specific collection of pollen, and this is mainly based from the types of plants and trees that are present in the area. If a crime was performed within a forest, then the pollen that could be collected on the body of the victim should be of those that were derived from the plants and trees of that same forest. If the pollen collected from the body of the victim is different from those that are present in the area, then it is most likely that the victim was murdered in another area and subsequently transported to the current area. As forensic science is currently considered as a powerful method in the presentation of evidence in criminal cases, it is thus important that the collection of biological samples be performed in a very cautious and systematic way. One of the most important factors to consider during the collection of biological material is the avoidance of contamination. Each biological sample should be collected aseptically, wherein materials and containers should be free of reagents and other materials that could result in erroneous forensic analysis. Each piece of biological evidence should thus be picked up using clean forceps or gloves and immediately kept in sterile containers such as plastic bags, test tubes or containers. Biological evidences should also be properly labeled, indicating the date and time of collection, as well as the approximately place of collection within the crime scene. It would also be helpful that photographs of the entire crime scene be taken first before any collected of biological material is performed. It is also important to keep all biological evidences free from any bacterial contamination, as this may result in the generation of DNA from both the individual of interest and the bacterial species. When bacterial DNA is present in the sample, the STR analysis may generate misleading and confusing results. Biological samples should also be collected using extreme caution from heat because DNA and other proteins are highly likely to be degraded by extreme temperatures. One of the most difficult criminal cases that involve forensic analysis are those associated with fires, as most of the cells and the DNA of the victims have been destroyed by the heat. This results in the difficulty of identifying the victims of the crime, as most of the evidence has already been destroyed. In such cases, the bones and the teeth of the victims are usually collected for forensic DNA analysis, as these parts of the body are somehow resistant to heat and destruction. The DNA banding pattern could be correlated with any other non-biological evidences that may still be present in the body of the victim. References Giardina, E., Pietrangeli, I., Martone, C., Zampatti, S., Marsala, P., Gabriele, L., Ricci, O., Solla, G., Asili, P., Arcudi, G., Spinella, A. and Novelli, G. (2009). Whole genome amplification and real-time PCR in forensic casework. BMC Genomics, 10, 159-163. Hunter, P. (2006). All the evidence. EMBO Reports, 7, 352-354. Nazni, W.A., Jeffery, J., Sa'diyah, I., Noorjuliana, W.M., Chen, C.D., Rohayu, S.A., Hafizam, A.H. and Lee, H.L. (2008). First report of maggots of family Piophilidae recovered from human cadavers in Malaysia. Tropical Biomedicine, 25, 173-175. Read More