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Introduction
Introduction
In Fall 2024, I took FIS-I420: Forensic Biology. This class focused on the biological applications of forensic science. Everything from the makeups of various bodily fluids, to the intricacies of the tests used to detect them were discussed in depth. For my honors project, I teamed up with my classmates Joy Corbett and Sara Hartley. Our professor, Dr. Ryan Eller, wanted us to test out whether the type of laundry detergent he bought worked better than the average detergent, since it was advertised to get out any stain.
We took several different kinds of fabric and stained them with our own blood (by using a fingerstick) and saliva. We washed our control groups in the laboratory sink with the normal Tide pod, and then washed our test groups with the Dr. Eller's Hygienic Clean. After drying them with a hair dryer, we then used different forensic tests to test for the presence of blood and saliva on the cloths, indicating if one had cleaned up better than the other.
Summary
Summary
In order to complete this project, we needed to use tests that target both human blood and saliva. First, presumptive tests were completed. These tests indicate that the substance might be present. If these tested positive, the plan was to move on to confirmatory testing. Confirmatory testing does just as it says and confirms the presence of that substance. In this case, the only test for saliva that we had access to was the presumptive Starch-Iodine test. All of these ended up testing positive for both the control and test groups. This indicated that the saliva had not washed away.
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The Kastle-Meyer test was then used as a presumptive test for blood. Once again, all of the samples for both groups tested positive, indicating that there may be blood present after the wash. To confirm this, we turned to the RSID blood kit. After completing the tests, we found that all of them appeared to be negative, contradicting the presumptive tests. This told us that we got false positives in all of our presumptive blood tests. This also made us question the presumptive saliva tests, since we did not have a confirmatory test for them.
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After doing some digging, we discovered that both the normal Tide pod and the Hygienic Clean products have amylase enzyme in them. This is the very thing that is in our saliva, and the very thing that can provide a positive result in the Starch-Iodine test. We decided that the saliva tests were most likely false positives, telling us that saliva was present when, in reality, it was not. The thing that was most confusing to us were the positive results on our Kastle-Meyer tests. We knew there was no blood thanks to the RSID kits, so why did the presumptive tests test positive? After getting stuck on this, we decided to turn to Dr. Eller who quickly realized he had made a batch of bleach in the sink we had used. Bleach can cause the Kastle-Meyer test to provide a positive result, which is what we assumed happened here.
Reflection
Reflection
Needless to say, our experiment did not go as planned. None of us knew that amylase enzyme was an ingredient that Tide commonly uses, nor did we know about Dr. Eller's batch of bleach. False positives happen in the world of forensic science, so it was good to see it play out in our project and determine why the results were what they were. This project taught us a lot about problem solving and gave us a very good understanding of how these forensic tests worked and how easily the presumptive tests could provide false results.
Forensic scientists need to be as perfect as possible when handeling evidence and testifying about it. Because of this, it is important to realize where mistakes were made, how to fix them, and why they occurred. Being able to explain these mistakes to a court and confidently state why they happened and how they were corrected (if need be) is a large part of why this project turned out to be extemely helpful to my future career as a forensic biologist.
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