Future Applications of Forensic DNA Analytical Methods
Following the description of the structure of deoxyribonucleic acid (DNA) by Nobel Prize laureates Francis Crick and James Watson in 1953, a vast array of applications have emerged based on this structure. Indeed, scientists are identifying innovative ways to treat a host of human ailments based on this discovery, and future research will undoubtedly continue to identify additional applications for this information. Other researchers have also found ways to use DNA for forensic applications. To determine what these applications are and how they are being used, this paper provides a review of the relevant literature to identify current applications and limitations of DNA-based methods using in forensic analysis. An examination of the current forensic literature with respect to DNA-based methods, including an overview of how DNA is being used, a discussion concerning the possible limitations to the use of these methods for forensic purposes and an analysis of potential future applications of these technologies. A summary of the research and important findings are presented in the conclusion.
Review and Discussion
Basic principles of DNA analysis methods
Research in the early 1950s by Crick and Watson led to the description of the double-helix structure of DNA in 1953, for which they were jointly awarded the Nobel Prize for Physiology or Medicine in 1962 (Edelson 1998). According to Meyer, "In recent years, huge advances in DNA technology in general had already been made, meaning that the analysis of DNA was becoming ever more sophisticated. It had become an important tool for studying various aspects of living species, and it was now a routine task to take a sample of blood from a living animal, extract the DNA and carry out experiments on it" (2005, p. 38). The analytical methods used for DNA to identify individuals typically involve forensic scientists scanning 13 DNA regions, or loci, that differ from individual to individual (Drell, 2009). This information is then used to develop a so-called "DNA profile" for that individual (sometimes called a DNA fingerprint). There is an extremely small chance that another person has the same DNA profile for a particular set of 13 regions (Drell, 2009). According to Zedlewski and Murphy, "When law enforcement officers arrive at the scene of a major crime, they routinely collect biological evidence: blood, semen, hair strands. The evidence goes to the crime lab, where forensic technicians analyze the DNA and run the 'profile' against the national, State, or local DNA database, hoping to get a 'hit' or match that will help bring the offender to justice" (2006, p. 2). The first instance of DNA evidence being used to convict a criminal (in this case, rape) occurred in Great Britain in 1987 (Hammond 2010).
In the United States, DNA samples are maintained in the COmbined DNA Index System which combines computer-based applications with various DNA technologies (discussed further below). The CODIS uses two different indexes to produce potential forensic evidence based on biological samples obtained at crime scenes:
1. The Convicted Offender Index. This index contains DNA profiles of individuals who have been convicted of felony sex offenses as well as other types of violent crimes; and,
2. The Forensic Index. This index contains DNA profiles that have been produced using biological evidence from crime scenes (Drell 2009).
The CODIS therefore represents an enormously valuable tool in establishing identity and allows law enforcement authorities at all levels to share and compare the DNA profiles they develop using this biological evidence (Drell 2009). According to Zedlewski and Murphy, "The real strength of CODIS lies in solving cases that have no suspects. If DNA evidence entered into CODIS matches someone in the offender index, a warrant can be obtained authorizing the collection of a sample from that offender to confirm the match. If the offender's DNA is in the forensic index, the system allows investigators -- even in different jurisdictions -- to exchange information about their respective cases" (2006, p. 2).
One of the first methods used for DNA forensic analysis was restriction fragment length polymorphism (RFLP) (Drell 2009), but this outdated technology largely been replaced by the other technologies used to analyze DNA samples for matching with repositories described in Table 1 below.
Basic DNA analytical methods
Polymerase chain reaction (PCR)
This analytical method reproduces copies of a DNA sample from a tiny fragment and can be used for forensic analysis of biological samples that may have been degraded as a result to exposure to environment elements (Drell 2009).
Short tandem repeat (STR)
This method, which is used by the U.S. Federal Bureau of Investigation, analyzes specific loci contained in nuclear DNA based on the standard set of 13 specific STR loci contained in data repositories such as CODIS (Drell 2009).
Mitochondrial DNA analysis
This method analyzes DNA samples that cannot be examined with the other techniques described above (Kaestle, Kittles, Roth & Ungvarsky 2006). This method is especially useful for analyzing biological samples that may be several years old (Drell 2009).
Finally, this method is used to identify genetic markers on the Y chromosome which is inherited by sons from their fathers, making is particularly useful in establishing relationship between males, or for analyzing biological evidence that was obtained from several males (Drell 2009).
Low copy number (LCN)
Although not as widely used as some other analytical methods, this approach has been used by forensic scientists to develop profiles from exceedingly small sources of DNA (including perspiration); however, it is time-consuming and expensive and its use has been reserved for the most serious types of crimes to date (Pepper 2005). The use of this technique was temporarily suspended in the UK due to concerns about its reliability, but its efficacy has been confirm and its use has since been reinstated (O'Connor 2008).
Single-nucleotide polymorphism (SNP)
This method is used to detect differences in unique gene expression by identifying the presence of small modifications in the DNA that occur naturally and differentiate one person from another (Walter, McWeeney, Peters, Belknap, Hitzemann & Buck 2008).
Allele-specific polymerase chain reaction (PCR)
This technology, developed during the early 1990s, allows forensic scientists to amplify small amounts of DNA (as small as a billionth of a gram) (Pepper 2005). This method has been shown to be a cost-effective method of genotyping single nucleotide polymorphisms and mutations (Wangkumhang, Chaichoompu, Ngamphiw, Ruangrit, Chanprasert, Assawamakin & Tongsima 2007). The effectiveness of this method has been shown to be enhanced when chemically modified primer probes are used (Sterath, Detmer, Gaster & Marx 2007).
Current applications of DNA analysis for forensic investigations
Given its potential for accurately establishing identity, it is not surprising that law enforcement authorities have used DNA analysis for a wide range of forensic investigations. According to Caines and Gabriele, "Law enforcement/forensic science use applications in which DNA information generates a genetic profile to serve as an identification tool. The profile is defined and stored in a database, and a sample is then stored in a DNA repository for future analysis at the discretion of a law enforcement agency" (2004, p. 33). The use of DNA for these types of forensic investigations has been facilitated in large part by the creation of tissue repositories in the United States such as the National Pathology Repository and the DNA Specimen Repository for Remains Identification and the repository at the U.S. government-funded National Institutes of Health (NIH) that contain several million specimens (Tutton & Corrigan, 2004). Likewise, the United Kingdom has established a National DNA Database that is used by the forensic science service for criminal investigations (Tutton & Corrigan, 2004).
Some other common uses for DNA forensic identification applications include the following:
1. Identify potential suspects whose DNA may match evidence left at crime scenes;
2. Exonerate persons wrongly accused of crimes;
3. Identify crime and catastrophe victims;
4. Establish paternity and other family relationships;
5. Identify endangered and protected species as an aid to wildlife officials (could be used for prosecuting poachers);
6. Detect bacteria and other organisms that may pollute air, water, soil, and food;
7. Match organ donors with recipients in transplant programs;
8. Determine pedigree for seed or livestock breeds; and
9. Authenticate consumables such as caviar and wine (Drell, 2009).
Some of the potential advantages and disadvantages of banking DNA samples of individuals who have been arrested and charged with a criminal offense are listed at Appendix A.
Potential future applications of DNA analysis for forensic investigations
Despite the potential for abuse by law enforcement and other governmental and institutional authorities, it is reasonable to suggest that an extension of current trends in DNA analysis into the future will see an ever-increasing database of DNA samples, perhaps including most of the people on earth by the mid-21st century. Likewise, Caines and Gabriele note that, "Without question the global outpouring of concern over the events of September 11th makes extremely understandable a desire to use DNA profiling to discover the identity of any potential terrorist" (2004, p. 32).…