Trace Evidence Essay Example | Topics and Well Written Essays - 750 words

Trace Evidence - Essay Example 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