Table of Contents
Materials and Methods.
The study that is being critically analysed is based on the aim of finding out the possibilities of detecting the DNA after scrubbing surface of the objects such as textile and smooth services. The article contains a good summary of the existing knowledge in the field as there is a number of information that shows though DNA is a highly reliable source of information for solving a crime at the court, it all becomes difficult by the possible attempts of the criminals to remove the traces by cleaning the surfaces of the crime scene as it is easy to remove the visible parts of blood or semen or others source of DNA. There is also information regarding correlation of the success of cleaning and the surface being cleaned (Helmus et al., 2019).
A gap in the existing knowledge has been shown by questioning the cause of transfer of DNA from one surface to the other. The aim of the current study addresses the gap as studying whether cleaning an object may cause DNA traces to be distributed. Through this, the question regarding chances of the DNA changing from one position to the other can be solved. The gaps in the existing knowledge’s have been supported with the relevant research studies which lead to the effectiveness in statement of the gaps. For instance, studies working on DNA and STR analysis associated with cleaning the crime scene objects have been discussed. Research has been done before on similar contexts before, and the article makes use of technology that is relatively modern with an example being the Polymerase Chain Reaction (PCR) testing methods. However, technologies currently in use rely on higher computational dynamics, which limit the time-based validity of the article in question.
There is enough details regarding the place of collecting sample which is the Institute of Legal Medicine, Germany, the experimental set-ups and the items and materials used in the current study has been discussed. The samples included blood, saliva, cell line DNA and epithelial cells collected in fabric or from touching a table with hand in 15 N pressure or rubbing the area with neck skin cells on cloths. The process in which the samples were placed has also been clearly indicated in the method of the study. The size of the table used in the study, length and width of the table and cloths used, the cleaning agents used to clean the surface areas and the process of DNA extraction have been elaborated which will help in completing the current research by another researcher.
There were negative controls where after cleaning the fabric and the table surface has been indicated before starting any new scenario. This has improved the attempt to reduce the chances of masking the authentic results to be gathered in different experimental conditions due to the presence of any DNA remnants. It comprised fabrics, table surface and sponge which further ensure that the results of cleaning different surfaces with different cleaning agents can be achieved. The controls therefore can be considered as enough and appropriate used in the current study (Schneider-Poetsch & Yoshida, 2018). There were enough replicates in the study used such as sponge and the table surface along with the fabric has been used in different sizes. Apart from that, different cleaning agents have been used to wipe off or clean the surfaces. It has also been ensured that one condition of the experiment does not affect the results gained in another condition. Therefore, it can be stated that there were enough replicates to ensure reliable results.
The sample chosen in the study are needed to be selected appropriately so that it can achieve the aim of the research and fulfill the purpose of the researcher. Samples used from the “right upper corner, left and right lower corner” have resulted in 109 samples in total. This chosen sample is justified with the aim of reducing the impacts of previous experiments on the later ones. For instance, different places have been used to reduce the ordering bias which could affect the reliability of the result. In other experimental conditions the researcher has created four samples for all the eight cleaning agents with different amounts of body fluids. It is justified as different body fluids used in different conditions may have different position in the context of distribution of the DNA.
The results are clear and effective for understanding as DNA concentrations in different experimental set-ups have been developed through using real time PCR. Along with this, the results have been presented in graphs differentially identifying the performances of the cleaning agents in removing the DNA concentrations from different surfaces. The current study has also used statistics to where concentration of the DNA has been studied corresponding with STR analysis. For instance, samples that comprise of DNA below 0.001 ng/μl were considered to demonstrate no profile. This statistical base line has provided the researcher to compare results of every experimental conditions of the current study. Therefore, the significance of the results has been decided based on this ground rule statistical base to make the answers comprehensible. The table and figures used for graphical representation of the results gathered from the current study has been clearly depicted and visible to the readers. These are easy to comprehend and the images are of high quality. For instance, in the first experimental set up, it is clearly understandable that partial profiles took place in samples in very low amount from the surface of the table which is 13% though the amount is high in the case of textile which is 35%.
The results from second experimental set up has also been presented in graph where a clear symbolization of the different agents used has been indicted along with the micro liter amount of saliva and blood. The variations of the profiles such as complete profile (CP), Partial Profile (PP) and No Profile have been mentioned to provide the readers a clear understanding. Moreover, the concentration of each of the sources such as blood, saliva and epithelial cells has been differentiated by depicting the same in separate charts.
The figures and captions have appropriate titles, captions and labels throughout the article. For instance, at the starting of the research existing knowledge regarding the same topic has been shared and main issues regarding the topic faced by the investigating authorities have also been depicted and the aim of the study has been shared. This can be considered as effective introduction as readers will be well aware of the reason and value of the study being conducted (Leatherdale, 2019). Apart from that method and materials used in the current study has been described under comprehensive section names such as artificial scenario where the sample collection process and development of the experimental set-ups have been shared in a comprehensive manner. Additionally, the tables and graphs also have captions and titles that carry the adequate introduction of results to be presented.
The information shared through figures and tables are consistent with the text written. The information provided in pictorial and numeric forms have been clearly elaborated through using comprehensive texts. As shown in the figure “blood Table” the entire blood sample from the surface of the table irrespective of the time taken to dry it, addition or omission of soap has shown complete profile. This information has been clearly described in text depicting that the attempt of cleaning the original stained area will have the potential to distribute DNA from blood cells over a large area. Therefore, there is congruence between the information shown in the tables and results described through the use of text.
There are more than 300 samples and all were separately used in order to fulfil the purpose of the current research. After thoroughly describing the obtained results in the case of each of the samples, the researchers considered and tied all the results together. In doing so, the researchers have compared different sampling areas. For instance, authors of the study have shown that comparatively the “drop point of blood and saliva” demonstrated complete profile in predominant manner despite of several attempts for cleaning. As compared to this, a complete profile has been displayed by the second and the third sample by 68% and 14% respectively. The partial profiles have also not displayed complete profile to the extent the first area has shown.
Thus, the authors have come to the end point of their discussion that even if the cleaning agents are used there is a high possibility of DNA distribution by cleaning. However, no limitations have been identified to be indicated by the authors which has been attempted to be addressed by them. The current study has suggested for future researchers to include “dirt free areas or use cleaning cloths in a routine analysis” as there is always a possibility for clean areas in the naked eye in leading to complete profile.
The current study is reasonable to put value in their results as it indicates that the amount of transfer that is required for a complete profile is unlikely for DNA from epithelial cells. However, the distribution of DNA is largely probable in case of saliva or blood source of DNA. Thus, it has provided inputs to the forensic community’s knowledge base that contact directly with the body or the belongings are less likely for DNA transfer as compared to saliva or blood which will help the community to consider the sample that will adequately provide evidence for the victims (Wienroth, 2018).
The authors have noted that the aim of the study has been achieved as the question which triggered the current study has been answered successfully which has led the researchers to meet the aim.
The current study can be considered of a good quality for some different reasons describes below. The study has started with an aim for supporting the forensic community to find the answer to the question “if the DNA has the possibility to be distributed from one actual position to several others through cleaning up the whole car with chemical detergents”. In doing so, the problems found out by different studies related to the current topic has also been summarized which provides the readers with overall idea and understanding of the purpose of the study. The methods and materials used in completing the research have been clearly defined that it can be replicated by any other researcher. On the other hand, different experimental conditions have been differently studied which has provided in depth understanding about the probability of DNA transfer in case of different surfaces. The graphs demonstrating the results have increased comprehensiveness of the results obtained. Additionally, the current study has also effectively answered the main question of the research.
Helmus, J., Pfeifer, M., Feiner, L. K., Krause, L. J., Bajanowski, T., & Poetsch, M. (2019). Unintentional effects of cleaning a crime scene—when the sponge becomes an accomplice in DNA transfer. International journal of legal medicine, 133(3), 759-765.
Leatherdale, S. T. (2019). Natural experiment methodology for research: a review of how different methods can support real-world research. International Journal of Social Research Methodology, 22(1), 19-35.
Schneider-Poetsch, T., & Yoshida, M. (2018). Along the Central Dogma—Controlling Gene Expression with Small Molecules. Annual review of biochemistry, 87, 391-420.
Wienroth, M. (2018). Governing anticipatory technology practices. Forensic DNA phenotyping and the forensic genetics community in Europe. New Genetics and Society, 37(2), 137-152.
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