Helping Solve "Whodunnit": Determining the Number of Contributors in a Sample Earlier in the Forensic Workflow [online video]


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7th Annual VCU 3MT® Competition, held on October 15, 2021.


The research involves developing a tool to earlier identify DNA from multiple sources in forensic samples.


Chastyn Smith: We've all probably seen a crime mystery show at some point, whether it was Scooby Doo or true crime. So let's play "whodunnit." We arrive at a crime scene and we see this puddle of blood. We take a sample of the blood, and we send it to the lab for testing. In the lab, the sample is taken through the old workflow only to reveal at the end that it contains DNA from maybe one, maybe two people. We can't be quite sure because all the DNA is not crossing the level of detection. Now we could reanalyze this sample, and hope for better results, but this process already took weeks, and at most it could take months. This is a problem in the forensic DNA community. Samples that contain DNA from multiple individuals, called "mixtures," produce complex results like the picture on top, and are not revealed until the end of the workflow, at which point it's too late to do things differently in order to get better results. Now, a solution would be to detect that a sample is a mixture earlier in the workflow so that we could then know to modify how we process that sample so that we can ensure we get better results later on, like the sample on the bottom. Well, this is what my research is. I am developing a tool that can be used earlier in the forensic workflow that will determine if a sample is a mixture. The way this tool works is we look at two different regions of the DNA that differ between individuals. The more differences that are seen, the more likely that sample contains DNA from multiple people, and the tool predicts it to be a mixture. And the good thing about this tool, is that it is combined with a step that's already in the workflow, so it doesn't add an increase in time. So far, in proof of concept testing, this tool has been able to accurately identify 90% of the mixtures tested. Further research will be done to, one, increase the accuracy of this tool, and to develop more features. For example, we not only want this tool to tell you that a sample contains DNA from multiple people, but exactly how many people. The most immediate impact of this research will be seen in DNA labs, as it will allow for more samples to be tested, which could be the determining factor in a case. But looking at the bigger picture, this research is significant to society because it is bettering the DNA analysis process by allowing stronger results to be obtained the first time a sample is analyzed. This will allow cases to be solved faster, the majority of which are committed by repeat offenders. So if we can stop a re-offender before they offend again, this will ultimately lead to a decrease in crime.


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