DNA Comparison

DNA Comparison

There’s always that one scene in crime show thrillers—the one where the the lab technician in a white lab coat nails the killer by extracting or finding the smallest amount of evidence through DNA. Blockbusters also seem to do the same thing. The witty, nerdy, and attractive lab tech turns around evidence in a short matter of time and the there’s almost always a happy ending. 

Crime > Investigation > Trial. The story line remains relatively the same.

Seems quite simple on the big screen, but in fact these types of scenarios Hollywood perpetuates for their audience actually causes more problems than solutions. DNA evidence is often not found in most cases and without DNA, most jurors are hung because they lack this “gold standard” of evidence they see quite often on television. DNA also puts away innocent individuals and costs people their livelihoods. DNA has become the golden standard of all forensic sciences in the twentieth century but even science has its shortcomings.

What is DNA?

DNA stands for deoxyribonucleic acid (nDNA) and is “the molecular structure in all living things containing their genetic information” (Shelton 27). Even though a crime may have been committed years earlier (depending on the preservation), DNA can still be extracted from the smallest remains. According to Shelton, DNA started “as a method of determining paternity” and is now the used in every jurisdiction throughout the country (27). DNA analysis is only one of many forensic methods, but the National Academy of Sciences (NAS) have found that “among existing forensic methods, only nuclear DNA (nDNA) analysis has been rigorously shown to have the capacity to consistently, and with a high degree of certainty, demonstrate a connection between an evidentiary sample and a specific individual or source” (Shelton 27). Methods and procedures pertaining to the admissibility of DNA evidence is consistently changing and are not universal throughout the U.S. There are in fact different types of analysis and procedures. For DNA analysis, there are two methods known as the (1) nDNA method and (2) mitochondrial DNA, and the nDNA testing is the most discriminating, while the second has more leeway. “DNA testing also does not really produce a match between two samples, but instead describes the statistical likelihood that the evidence sample came from someone other than the defendant” (Shelton 28). Another myth debunked from hit TV shows. It’s not really a match but more less a statistical factor.  

Three types of methods are used to generate DNA profiles: restriction fragment length polymorphism, polymerase chain reaction (PCR), and short tandem repeats test. PCR-based DNA methods are routinely used because of its reliability and solid scientific foundation that is accepted by the scientific community. However, not all sciences are foolproof. With continuous reconstruction and evaluations of guidelines regarding DNA analysis, DNA testing can also help produce wrongful convictions.

Problems with DNA Analysis

“According to the Innocence Project, ‘Of of first 225 wrongful convictions overturned by DNA testing, more than 50% (116 cases) involved invalidated or improper forensic science’” (Acker 316). These cases and many alike are not only subjected to improper handling of evidence but also involve expert testimony from “experts” that have actually cost individual’s their lives. The validity of the evidence and the expert testimony are often not met due to human error and therefore NAS has set strict guidelines. “Two important questions underline the law’s admissibility of and reliance upon forensic evidence in criminal trials: (1) the extent to which a particular forensic discipline is founded on reliable scientific methodology that gives it the capacity to accurately analyze evidence and report findings and (2) the extent to which practitioners in a particular forensic discipline rely on human interpretation that could be tainted by error, the threat of bias, or the absence questions are significant (Acker 318). So it matters a great deal on whether the expert is qualified and whether the evidence is reliable. Finally, jurors are also not well versed with scientific terms or the fundamentals of any science (medicine, physics, chemistry, neurobiology, and related disciplines) and can be a factor in determining a wrongful conviction.

Citation
Acker, James R., and Allison D. Redlich. Wrongful Conviction: Law, Science, and Policy. Carolina Academic Press, 2011.
Shelton, Donald E. "The "Who" Question." Forensic Science in Court: Challenges in the Twenty-first Century. N.p.: Rowman & Littlefield, 2011. pp. 39-50. Print.