Introduction
DNA analysis, or the study of deoxyribonucleic acid, has revolutionized the field of criminal investigations. The ability to extract, analyze, and compare DNA samples from crime scenes, suspects, and victims has led to a greater understanding of crime and the criminal mind, improving the reliability and accuracy of criminal investigations. Advancements in DNA analysis technology have enabled the study of DNA samples in greater detail, thereby increasing the likelihood of finding a match. Additionally, the use of DNA databases, such as the national DNA database (CODIS) in the United States, has enabled the rapid and efficient comparison of DNA profiles (Oosthuizen & Howes, 2022). To fully understand the importance and impact of DNA analysis used in criminal investigations, this essay will discuss its history, methods, databases, applications, and associated concerns.
History of DNA Analysis
DNA analysis has a rich history that has evolved. A discovery of DNA dates back to the 19th century, when Swiss physician Friedrich Miescher first isolated a substance he called “nuclein” from the nuclei of white blood cells (Tsuji et al., 2019). In the following decades, scientists such as James Watson and Francis Crick worked with data obtained by Rosalind Franklin and Maurice Wilkins (Tsuji et al., 2019). As a result, they discovered the double helix structure of DNA, revealing it as the genetic material that carries the instructions for the development and function of all living organisms.
DNA fingerprinting, the first practical application of DNA analysis in criminal investigations, was developed in the late 1970s by British geneticist Alec Jeffreys (Tsuji et al., 2019). Jeffreys found that certain DNA regions, called “minisatellites,” vary significantly among individuals and can be used to generate a unique DNA profile. (Tsuji et al., 2019). This profile could then be compared to DNA samples from crime scenes or suspects to establish a match.
Since the development of DNA fingerprinting, DNA analysis technology has undergone significant advancements. Polymerase Chain Reaction (PCR) technology, which amplifies small amounts of DNA, was developed in the 1980s, allowing for the analysis of smaller and more degraded DNA samples (Oosthuizen & Howes, 2022). In the 1990s, Restriction Fragment Length Polymorphism (RFLP) analysis and Short Tandem Repeat (STR) analysis were developed, providing more robust and reliable DNA profiles (Tsuji et al., 2019).
In recent years, even more advanced DNA analysis methods have been developed. Whole-genome sequencing, which analyzes the entire genome, has become increasingly cost-effective, allowing for the detection of more genetic variations and a more sensitive identification of suspects. New technologies, such as Rapid DNA analysis, which can produce a DNA profile in under 90 minutes, have been developed for use in forensic and field settings (Tsuji et al., 2019). The history of DNA analysis has been a journey of discovery and innovation, leading to a deeper understanding of genetics and a wide range of practical applications in various fields.
Methods of DNA Analysis
Several methods are employed in DNA analysis, each with its advantages and disadvantages, and are best suited for different types of samples. As mentioned above, the Polymerase Chain Reaction has allowed the analysis of smaller and more degraded samples. Consequently, PCR is ideal for samples with small amounts of DNA, such as hair, saliva, or blood stains. (Tsuji et al., 2019).
The main disadvantage of PCR is that it can introduce errors into the amplified DNA, and there are several reasons for this. First, PCR relies on a polymerase enzyme to replicate DNA, and this enzyme can make mistakes during the replication process. Second, PCR uses short pieces of DNA called primers to initiate the replication process. Sometimes these primers can bind to each other, forming “primer-dimers” which can be amplified along with the target DNA, introducing errors into the amplified DNA (Oosthuizen & Howes, 2022). While these factors can make this method less reliable, it remains effective and is commonly used in crime investigations.
Another method is Restriction Fragment Length Polymorphism, which cuts DNA at specific locations, creating patterns of fragments unique to each individual. RFLP is best suited for samples that contain large amounts of DNA, such as blood or semen stains. Additionally, it enables the analysis of various genomic regions, yielding a high-resolution DNA profile (Tsuji et al., 2019). However, the method is relatively time-consuming and requires large amounts of DNA. As a result, it is less sensitive than some other techniques and may be unable to detect small amounts of DNA. RFLP can also be described as a low-throughput method, meaning that only a limited number of samples can be analyzed simultaneously.
Short Tandem Repeat (STR) analysis is a method that analyzes specific regions of DNA known as microsatellites, which are highly variable between individuals and can be used to create a unique DNA profile. STR is best suited for samples that contain small to moderate amounts of DNA, such as hair or blood stains (Oosthuizen & Howes, 2022). Additionally, STR is a high-throughput method, allowing for the simultaneous analysis of many samples. It is also more sensitive and reliable than RFLP, and is the standard method used in most forensic DNA laboratories.
Finally, whole genome sequencing (WGS) analyzes an individual’s entire genome, providing a much more detailed and sensitive DNA profile. It is best suited for samples that contain high amounts of DNA, such as blood or semen stains. It is more sensitive than other methods, but also more expensive and time-consuming. This method requires specialized equipment, a large amount of reagents, and several days or even weeks to complete (Qureshi et al., 2021). As a result, WGS is not yet widely used in forensic DNA analysis due to its high cost, complexity, and limited ability to provide information specific to forensic investigation.
DNA Databases
DNA databases are collections of DNA profiles stored in a computerized system and can be searched against to find potential matches between crime scene evidence and known individuals. The most widely used DNA database in the United States is the Combined DNA Index System (CODIS), which is maintained by the Federal Bureau of Investigation (FBI) (Tsuji et al., 2019). CODIS is a system that enables the sharing and comparison of DNA data across local, state, and national laboratories.
DNA samples are collected from crime scenes, suspects, and convicted offenders, and are analyzed to create a DNA profile. The profile is subsequently uploaded to CODIS, where it can be compared with other DNA profiles in the system. Once a DNA profile is entered into CODIS, it is stored in one of three indexes: the convicted offender index, the arrestee index, and the forensic index (Parsons et al., 2019). The Convicted Offender Index includes DNA samples of convicted criminals, the Arrestee Index includes DNA samples of arrested individuals, and the Forensic Index includes DNA samples from crime scenes.
When a DNA profile is entered into CODIS, it is searched against all three indexes to see if there is a match. If a match is found, the investigating agency is notified, and the match is used to identify suspects and link crimes. If there is no match, the DNA profile remains in the database and is searched again when new DNA profiles are entered. It is worth noting that CODIS and other DNA databases are subject to strict regulations to protect individuals’ privacy and civil rights. For example, in the United States, DNA samples and profiles are collected and retained only for certain crimes, and the profiles are removed from the database if the individual is cleared of the crime or if a specific period has passed.
Sample Collection
There are several best practices for collecting DNA samples from crime scenes and suspects, designed to minimize contamination and preserve the integrity of the samples. First, DNA analysts must use proper personal protective equipment (PPE) (Parsons et al., 2019). When collecting the samples, they should wear gloves, face masks, and other PPE to avoid introducing their own DNA to the samples. Second, sampling equipment and areas should be distinct for each sample; separate tools, such as swabs, combs, and scissors, should be used to prevent cross-contamination between samples.
Additionally, DNA samples should be collected, packaged, and labeled to maintain a chain of custody, which documents everyone who has handled the samples and when. This helps to ensure the integrity of the samples and the accuracy of the DNA analysis (Parsons et al., 2019). All samples should also be stored in a way that preserves the integrity of the DNA, such as refrigeration or freezing.
It is essential to note that different types of samples have varying storage requirements, so it is crucial to follow the instructions provided by the DNA analysis laboratory. Only validated methods for collecting and preserving DNA samples should be used, as they have been proven effective in maintaining the integrity of the samples. Finally, it is essential to document the collection process, including date, time, location, type of sample, and the name of the person collecting the sample.
Interpretation of DNA Evidence
Interpreting DNA evidence involves evaluating the similarities between DNA samples collected at a crime scene and those obtained from individuals of interest to establish if they match. The first step involved in this process is DNA profiling, when DNA samples are analyzed to create a set of specific genetic markers unique to each individual (Machado & Silva, 2019). A comparison is made between the DNA from a crime scene and that of a suspect or known person to see if they match (Machado & Silva, 2019).
Next, the likelihood of a match between the two DNA profiles is determined using statistical calculations. This is done by comparing the number of genetic markers that match between the two profiles to the total number of markers analyzed. Finally, the results are interpreted in the context of the investigation, taking into account other available evidence and information.
Applications of DNA Analysis
Several primary applications of DNA analysis can be identified in the context of criminal investigations. First, it is used to identify suspects; if a match exists, the suspect’s DNA profile can be used as evidence in the investigation. Second, it can identify victims by comparing their samples to those obtained from family members or other known individuals (Qureshi et al., 2021). This can be particularly useful in cases where the victim’s body is not easily recognizable.
Another critical application is linking crimes and suspects; this can be used to establish a pattern of criminal activity and link suspects to multiple crimes. DNA analysis can also be used to exonerate individuals wrongfully convicted by comparing their DNA to samples obtained from the crime scene. This can help to prove that the individual did not commit the crime and clear their name. Various DNA analysis methods can be used to solve old or cold cases (Parsons et al., 2019). Finally, DNA analysis can identify human remains in cases of mass disasters or unidentified human remains.
Nevertheless, there are also limitations and potential sources of error in DNA analysis, including concerns about sample quality, laboratory errors, statistical calculations, technological limitations, and the risk of false positives. The quality of the DNA sample can affect the accuracy and reliability of the DNA analysis. Degraded or contaminated samples can lead to inaccurate or unreliable results. Human error can also occur during the DNA analysis, such as contamination or mislabelling of samples. The statistical calculations used to determine the likelihood of a match are based on assumptions about the population and the frequency of the genetic markers analyzed. If these assumptions are not valid, the statistical calculations may not accurately reflect the actual likelihood of a match.
Moreover, DNA analysis methods and techniques constantly evolve, and not all laboratories can access the most advanced technologies. This can lead to limitations in the sensitivity and accuracy of DNA analysis, particularly in cases involving older individuals or those with limited resources (Qureshi et al., 2021). False positive results concern cases where a match is found where, in fact, there is no match. This can occur due to cross-contamination of samples, laboratory errors, or issues with statistical analysis.
DNA and the Courtroom
DNA evidence is commonly employed in criminal cases to determine whether a defendant is guilty or innocent. The admissibility of DNA evidence in court is governed by the rules of evidence, which vary by jurisdiction. However, DNA evidence is generally considered admissible in court if it is relevant and reliable. The process of admitting DNA evidence in court typically involves the testimony of a DNA analyst, who explains the scientific principles behind the DNA analysis and the results of the analysis. The defense may also call its own DNA expert to challenge the prosecution’s evidence or to provide an alternative explanation for the results.
Once DNA evidence is admitted in court, it can be used to establish the guilt or innocence of a defendant in several ways. For example, a DNA match between a suspect and a crime scene sample can be used to establish the suspect’s presence at the crime scene. Similarly, a DNA match between a suspect and a victim can be used to establish the suspect’s guilt (Qureshi et al., 2021).
However, potential challenges may arise during the trial when using DNA evidence. These include contamination, misuse of statistics, and interpretation of results. Contamination of DNA samples can lead to inaccurate results, making it challenging to determine whether a DNA match is the result of contamination or an actual match. Misuse of statistics can lead to inaccurate conclusions about the significance of a DNA match. Interpreting the results of DNA analysis can be complex, and experts may disagree on the significance of those results.
Ethics and Privacy Concerns
DNA evidence in criminal investigations raises several ethical and privacy concerns. First, collecting DNA samples from suspects and individuals who have not been charged with a crime raises ethical concerns about privacy and the potential for law enforcement abuse of power (Oosthuizen & Howes, 2022). Second, the storage of DNA samples raises concerns about the potential for the samples to be misused or mishandled, which can lead to privacy invasion and inaccuracies in DNA analysis. Sharing samples between law enforcement agencies and other countries raises concerns that the samples may be used for purposes other than solving crimes, such as genetic research or population tracking.
Moreover, the use of DNA databases can lead to racial and ethnic bias, as certain groups of people may be disproportionately represented in the database due to over-policing or discrimination in the criminal justice system. There are also significant privacy concerns: DNA analysis can reveal sensitive personal information about an individual, such as medical conditions or family relationships, which can affect their privacy (Machado & Silva, 2019). Ultimately, DNA testing can clear the names of those wrongly convicted, yet if mishandled, it may also contribute to wrongful convictions.
To mitigate these concerns, laws and regulations have been put in place to protect individuals’ privacy and civil rights. An example is the DNA Identification Act in the United States, which regulates the collection, storage, and sharing of DNA samples (Oosthuizen & Howes, 2022). Additionally, DNA analysis should be conducted by accredited laboratories, and experts in the field should interpret the results to ensure the integrity of the evidence and minimize the possibility of errors.
Conclusion
It can be concluded that DNA analysis plays a crucial role in criminal investigations, providing a powerful tool for identifying suspects, linking crimes, and exonerating the innocent. DNA evidence is widely used in criminal trials, and the rules of evidence govern its admissibility in court. However, its use also raises several ethical and privacy concerns that must be addressed to ensure the analysis is conducted reliably and accurately.
The future direction of DNA analysis includes the continued development of new technologies, such as next-generation sequencing, that will make DNA analysis faster, cheaper, and more sensitive. This will make it possible to analyze more complex samples, such as samples from old or degraded DNA, and to analyze more markers, increasing the power of the analysis.Additionally, utilizing artificial intelligence and machine learning in DNA analysis is a promising area of research that can potentially enhance the accuracy and speed of DNA analysis.
References
Machado, H., & Silva, S. (2019). What influences public views on forensic DNA testing in the criminal field? A scoping review of quantitative evidence. Human Genomics, 13(1). Web.
Oosthuizen, T., & Howes, L. M. (2022). The development of forensic DNA analysis: New debates on the issue of fundamental human rights. Forensic Science International: Genetics, 56(2), 102606. Web.
Parsons, T. J., Huel, R. M., Bajunović, Z., & Rizvić, A. (2019). Large scale DNA identification: The ICMP experience. Forensic Science International: Genetics, 38(3), 236-244. Web.
Qureshi, S., Prakash, R., & Gupta, S. C. (2021). Role of DNA profiling in criminal investigation based leading case laws. Journal of Mountain Research, 16(3), 171-178. Web.
Tsuji, S., Takahara, T., Doi, H., Shibata, N., & Yamanaka, H. (2019). The detection of aquatic macroorganisms using environmental DNA analysis—A review of methods for collection, extraction, and detection. Environmental DNA, 1(2), 99-108. Web.