Expanding the Use of RNA in Forensic Science: A Quantum Dot Molecular Beacon Approach

As the popularity of shows such as CSI increases, so does the demand for DNA evidence in court cases. This has led to the overwhelming of capacity for analysis of biological samples at crime labs across the country, and to the development of a massive backlog of DNA evidence waiting to be processed. At the end of 2011, labs had a processing capacity of 250,000 cases per year, but an annual total of nearly 350,000 that needed to be processed. Such delays have effects throughout the US justice system. One way to reduce the backlog would be to increase the value of the evidence retrieved from the scene, reduce the collection of unnecessary evidence, and retrieve as much data from the evidence as possible in the fewest steps. We investigated a novel, confirmatory method of body fluid identification using quantum dot molecular beacons (QDMBs). The QDMBs target RNA species that are tissue-specific or sex-specific, allowing for the identification of body fluid stains and identifying the sex of the depositor of a bloodstain. Our results show that we were successful in developing QDMBs that identify blood, semen, saliva, male blood, and female blood, along with a human-specific beacon. We were also able to detect aged stains, although the age detectable is dependent upon the particular fluid tested. This technique has a low cost, confirmatory testing, and a high potential for portability, meaning it could be performed at the scene to increase the value of evidence retrieved. In addition to being a confirmatory test, it does not lead to the degradation of DNA, as can some presumptive tests. We believe this technique holds great potential for increasing the value of RNA in forensic evidence and helping to reduce the biological evidence backlog