Date of Graduation
Eberly College of Arts and Sciences
Forensic and Investigative Science
With the current state of the field of forensic biology, collecting DNA from evidence samples may pose some difficulty. Traditional methods for collection of DNA from biological fluids and touch samples include cuttings, scrapings, and the double swab method. While all of these methods have benefits, they also have their drawbacks. In order to more efficiently collect DNA from an evidence sample, novel approaches need to be explored. This novel approach is the microbial vacuum (M-Vac®) Wet Vacuum System.
This system utilizes a sterile collection solution and a vacuum to collect DNA material from evidence samples. While it is similar to the double swab method, it takes collection a step further by collecting DNA material within the pores of samples. It is especially beneficial for cold cases where DNA material from the surface of a piece of evidence was previously collected but there was still trace DNA trapped in the pores. This method eliminates issues related to sample size and attempting to determine where to collect on a piece of evidence. It also has the benefit of sampling evidence areas directly and in its entirety. This can decrease the number of evidence samples needed to be transported to the laboratory for processing since the M-Vac® can be used at crime scenes. Therefore, this system is beneficial for its use as a serological tool for a crime scene analyst and a DNA analyst.
Some preliminary research has been performed by the Moroose Research Lab comparing the M-Vac®to traditional cuttings for collection of blood, saliva, and semen, and wet swabbing for touch DNA on unworn and 15-minute worn cotton t-shirts. The unworn study showed that the M-Vac®might be beneficial with the collection of touch DNA as compared to swabbing. As for the 15-minute worn study, it was shown that background wearer DNA has the potential to interfere with the interpretation of an evidence sample’s electropherogram when collected with the M-Vac® by being preferentially amplified over DNA from the evidence sample. However, with t-shirts being worn for 15 minutes is not very indicative of a true crime scene scenario. So, to determine the extent of interference wearer DNA can have on an evidence sample’s electropherogram when collected with the M-Vac®, a study with t-shirts worn for 12 hours was conducted.
This study was the same as the previous worn study conducted with the only difference being that the t-shirts were worn for 12 hours instead of only 15 minutes. T-shirts were worn by individuals for 12 hours consecutively and then a biological fluid or touch DNA was placed onto the worn t-shirt. Fluids were either blood, saliva, or semen. This new study helped to fill the gap of knowledge from the previous 15-minute worn study by determining the extent wearer DNA had on the quantity of human DNA and the electropherograms for evidence samples collected with the M-Vac® and traditional collection methods, such as a cutting or a wet swab, after a participant wore a t-shirt for 12 hours consecutively. Initially, based on the DNA quantity data, the M-Vac® was deemed to be less efficient than the traditional method of cuttings for the collection of blood, saliva, and semen, but more efficient for the collection of touch DNA. However, when reviewing the electropherograms, the M-Vac® outperformed the traditional method of cuttings for the collection of blood, saliva, and semen, and the traditional method of wet swabbing for the collection of touch DNA. Yet, this does come with one drawback. As the amount of wearer DNA starts to increase in quantity to either match the quantity of an evidence sample or exceed the quantity of an evidence sample, a mixture profile occurs and it becomes harder to reliably determine who the contributor is for the sample and the person who wore the t-shirt, especially if both sources are unknown.
Irion, Phillip Reilly, "Evaluating the Use of the M-Vac® Wet Vacuum System to Recover DNA from Cotton Fabric" (2020). Graduate Theses, Dissertations, and Problem Reports. 7951.